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I know that a diplobacillus is a bacillus bacteria that has a buddy 'attached' to it.
What I haven't been able to determine is exactly how is it 'attached'? Are their cell membranes fused - are they even touching? If they aren't fused, what keeps them together? Also, does this make diplobacillus a multi cellular organism because there are multiple cells in this organism?
I couldn't find anything about diplobacilli, but I did find some information on Streptococcus pneumoniae, which has been extensively studied. S pneumoniae (R6 strain) normally occurs as diplococci. Electron micrographs-see here and here-show that the two cocci of a pair share a portion of cell wall. This is a result of incomplete separation during cell division. Also, mutations in peptidoglycan-hydrolysing enzymes have been shown to produce longer chains of cocci.
Presumably, something similar holds for diplobacilli.
Calling these bacteria 'multicellular' might be inappropriate, because multicellularity implies at least some division of labour: the cells perform different functions in a cooperative manner. Diplobacilli (such as Moraxella lacunata) or diplococci have not been shown to have such a division of labour, as far as I know.
The Missing Link Between Psychology and Biology
The distinction between mind and body was unfortunately made centuries ago and remains with us today. We label illnesses caused by germs or viruses as "physical." We label other illnesses such as depression and anxiety as "mental." Yet the distinction between mental and physical is often unclear. For example, placebos are substances, such as sugar pills, that are thought to be physically inactive but can produce medical benefits in patients who believe they will work. In my book Cognitive Neuroscience and Psychotherapy, I point out that “Kirsch et al. (2008) reported that placebos are about 80% as effective as antidepressant medications are and 50% as effective as analgesic medications are. Kirsch and Sapirstein (1998) estimated that placebos were 75% as effective as antidepressive medications” (p. 252). The field of psychobiology studies placebo responses and other instances of mind-brain links. The field of biopsychology involves the reverse case it is concerned with ways that the physical body effects mental states. For example, it studies how legal and illegal psychoactive drugs alter the ways that we think, feel, and act.
Most people probably think of transitional fossils or species when they hear the term “missing link,” but another just as important missing link is the one between psychology and biology, between our physical and mental states. The terms psychobiology and biopsychology imply that psychology and biology are connected and interact. The problem with both psychobiology and biopsychology is that there is a missing causal explanatory link between mind and brain.
A very well accepted theoretical orientation in psychological science is the BioPsychoSocial (BPS) model. You might think that this model explains how psychology and biology interact, but you would be wrong. The BPS model is actually just a list of ingredients. It lists important biological, psychological, and social variables and claims that they mutually interact but does not provide any natural science mechanism information that can explain how they interact.
Some authors place these terms in boxes and draw arrows among them to impute causality but never provide any natural science mechanism information that actually explains how they physically interact. In short, the BPS model explains nothing more about how psychology and biology interact than explaining how a car works by listing that it is made of glass, metal, and petroleum. Listing is not explaining. Instead, the missing explanatory link is glossed over in hopes that you will either not notice or ask about it.
The most important task facing psychobiologists and biopsychologists is to provide a natural science explanation that links psychology and biology. This task requires identifying principles that provide mechanism information because mature sciences are organized around principles psychology is currently not. Those of you who have taken an introductory psychology course or who have read about psychology will recognize that psychology is currently organized around famous people, such as Freud and Skinner, or around “isms” such as behaviorism and cognitivism. This organization differs from all other natural sciences. They are organized around physical entities such as the cell in biology and molecules in chemistry. This allows biologists and chemists to explain more about how things work than psychologists can. Imagine how much better our therapies will become once we understand how and why they work.
I provide some of the missing explanatory details in my book entitled Cognitive Neuroscience and Psychotherapy: Network Principles for a Unified Theory. The remainder of this blog briefly presents the general conceptual framework for understanding how psychology and biology interact that my book is based on. I refer to this explanatory approach as a Bio«Psychology Network (BPN) explanatory system because it consists of four core and now nine corollary principles that together can explain a wide variety of well replicated psychological phenomena in ways that are fully consistent with neuroscience.
The first thing to understand is that our brains are made up of neurons that form neural networks. Hence, some form of network theory is required to explain how psychology and biology interact. How can these neural network models explain psychology? To answer that, we must first recognize that learning and memory form the basis of all psychology. Carlson, Miller, Heth, Donahoe, and Martin (2010) stated that: “Learning refers to the process by which experiences change our nervous system and hence our behavior. We refer to these changes as memories” (p. 440 italics in the original). Learning is crucial to human survival. If we could not form memories as infants, we could not learn to do anything. We would not develop language nor could we benefit from experience. In short, we would never develop into the children, adolescents, and adults that we are familiar with.
Rumelhart and McClelland (1986) and McClelland and Rumelhart (1986) provided demonstration proofs that artificial neural networks, called connectionist models, can form memories, can learn, and therefore can do psychology. Connectionist models of many psychological phenomena have been developed. The Psychological Review is a journal that specializes in psychological theory. It has published numerous long articles featuring connectionist neural network models. Many other demonstration proofs have been published in a wide variety of journals and books. Connectionist neural network models now rival traditional cognitive psychology models.
How Psychology Changes Biology
Here I sketch a general explanation that derives from parallel-distributed-processing (PDP) connectionist-neural-network (CNN) models that I collectively refer to as Computational Neuropsychology (CNP). Two major features characterize these models. The first major feature of these models is that they simulate neural architecture by using layers of simulated neurons. The second major feature of these models is that these simulated neurons are connected by simulated synapses. Artificial neural networks learn through training that modifies these synapses. Some synapses become more excitatory while others become more inhibitory of received activations. The difference between what the neural network computes as simulated behavior and the desired response is considered to be an error. These errors are used to modify the simulated synapses. These changes simulate the way that experience-dependent plasticity mechanisms modify real synapses in biological neural networks while they learn by forming memories. And then another learning trial begins. The network’s performance gradually improves through additional synaptic modification. Here we can see that learning is mostly about modifying synaptic connections.
But more brain changes are involved in psychological development. Infants are born with far more synapses than they will need as adults. Neural network pathways that are active while learning language, music, reading, writing, and playing sports, among other skills, are biologically reinforced by modifying synapses. Unused synapses are cannibalized to save precious metabolic energy. Psychological development literally, physically, sculpts the brain in addition to modifying synapses and thereby changes biology! Our brains physically specialize as we develop psychologically. This explains why it is more difficult for older people to learn a new language.
How Biology Changes Psychology
Our neural network understanding of how psychology changes biology prepares us to understand how biology modifies psychology. Understanding that the synapses that connect neurons contain our memories of who we are, the people that we know, the experiences we have had, and our attitudes about everyone and everything along with how we feel enables us to see that directly modifying them with legal or illegal psychoactive substances will change our psychology. Psychology normally changes our synapses by activating internal experience-dependent plasticity mechanisms. Drugs directly modify these same synapses pharmacologically and consequently alters our psychology. Pharmacological psychiatry is a relatively young field. The clinical practice of selecting the right medication to make therapeutic synaptic modifications is, by and large, a trial and error business. It can take several weeks for therapeutic effects to be noticed. Therapeutic effects are often dose dependent, which means that dosage may need to be systematically increased.
Neural network models enable us to see how psychology changes biology because the memory formation process that drives learning and all psychological development modifies synapses through experience-dependent plasticity neuroscience mechanisms. This knowledge enables to understand that modifying synapses pharmacologically will also change our psychology. The causal role of synapses in learning and memory make them the missing link in psychobiology and biopsychology. I predict that psychology will organize around the synapse when it becomes a mature natural science just as biology organized around the cell when it became a mature natural science. Subsequent blogs will present more by way of fascinating new developments—stay tuned.
Carlson, N. R., Miller, H., Heth, C. D., Donahoe, J. W., & Martin, G. N. (2010). Psychology: The science of behavior (7th ed.) (p. 196) Boston: Allyn & Bacon.
Kirsch, I., Deacon, B. J., Huedo-Medina, T. B. H., Scoboria, A., Moore, T. J., & Johnson, B. T. (2008). Initial severity and antidepressant benefits: A meta-analysis of data submitted to the Food and Drug Administration. PLoS Medicine, 5, 260-268.
Kirsch, I., & Sapirstein, G. (1998) Listening to Prozac but hearing placebo: a meta-analysis of antidepressant medication. Prevention and treatment, Vol. I, article 0002a, posted June 26, 1998, available at http://journals.apa.org/prevention/volume1/pre0010002a.html.
McClelland, J. L., Rumelhart, D. E., & the PDP Research Group (1986). Parallel distributed processing: Explorations in the microstructure of cognition, Vol. 2: Psychological and biological models. Cambridge, MA: MIT Press.
Rumelhart, D. E., McClelland, J. L., & the PDP Research Group (1986). Parallel distributed processing: Explorations in the microstructure of cognition, Vol. 1: Foundations. Cambridge, MA: MIT Press.
The Science Of Human Connection And Wellness In A Digitally Connected World
The most precious commodities on this planet are our health, love, and happiness. Regardless of what we accomplish and accumulate in life, we are unable to take it with us.
In the fast paced, consumer driven, social media shared world that we live in today, success and happiness are often defined by the status of what we achieve, and the value of the things that we own.
Everywhere we look, we are inundated with the same message: the measure of our self-worth is directly equal to the measure of our material wealth.
Whether it’s the status car, the trendiest clothes, the luxury home or the CEO title that comes with the envied corner office with a view, these and the many other status symbols of wealth and success seem to forever define our value in our culture today, immortalized by the cinematic perfection of super heroes and super stars, and broadcasted through the perfectly curated lives that bombard us daily by “friends” on social media.
Fueled by equal parts aspiration and expectation, in an entirely odd and unusual way, envy has become the 21st Century’s most enduring economic driver, feeding our most persistent social cravings and endless material consumerism.
In our effort to keep up with all that is expected of us — and expected of ourselves — many of us find ourselves in perpetual motion, filling our days with the hyper-active, turbo-charged, “crazy busy” schedules that keep us struggling to eat healthy, find and maintain balance between our work, busy careers, and all that’s happening in our personal lives. And despite our success, when we achieve it, it seems that quality personal time for ourselves and for nurturing our relationships has become increasingly more elusive.
Psychologists see a pattern in this success driven culture of busyness and the associated “connection disconnection” of an increasingly digitally remote world, and it’s triggering what they say is rapidly becoming a dire epidemic of loneliness. In the elderly, this epidemic of loneliness is known as the “hidden killer.”
With our daily use of email, texting, smart phones, professional and social media, we live in an age of instant global connectivity. We are more connected to one another today than ever before in human history, yet somehow, we’re actually increasingly feeling more alone.
No longer considered a marginalized issue suffered by only the elderly, outcasts or those on the social fringe, the current wave of loneliness sweeping the nation is hitting much closer to home than you might think. And as shocking as it may seem, new research shows that loneliness may now be the next biggest public health crises to face Americans since the rise of obesity and substance abuse.
In fact, loneliness and its associated depression has become downright rampant, even amongst some of the most successful, with studies showing that business executives and CEOs may actually suffer at more than double the rate of the general public as a whole, which is already an astonishing twenty percent.
What’s more, this ever-growing loneliness among the hyper successful is not just a result of the social and professional isolation of living in a more global and digitized world, but rather it’s a “lonely at the top” malaise that’s spreading largely due to the sheer emotional exhaustion of business and workplace burnout.
Science is now sounding the alarm that there’s a significant correlation between feeling lonely and work exhaustion — and the more exhausted people are, the lonelier they feel. This, of course, is made worse by the ever-growing trend for a large segment of professionals who now work mobile and remotely.
Throughout history, human beings have inherently been social creatures. For millions of years we’ve genetically evolved to survive and thrive through the “togetherness” of social groups and gatherings. Today, modern communication and technology has forever changed the landscape of our human interaction, and as such, we often decline without this type of meaningful personal contact. Today’s highly individualistic, digitally remote, and material driven culture is now challenging all of this, as we turn to science to unlock the mysteries of human connection and wellness in a digitally connected world.
Connection of Disconnection
In a world where some of our most personal moments are “Shared” online with “Friends”, business meetings are replaced with digital “Hangouts”, and the most important breaking news is “Tweeted” online in a mere 140 characters or less, today we often seem much more captivated by flashing notifications on our mobile phones than what we’re actually experiencing outside of our tiny 5'.7" screens.
Mobile technologies ushered in by Internet icons like Google, who have literally defined what it means to have “the world’s information at your fingertips”, have no doubt brought us one step closer to truly living in a “Global Village”. However, no matter how small the world may seem to be getting, it now also feels like it’s often becoming a much less personable place to live in as well.
This also means understanding just how much the “connection disconnection” of loneliness negatively impacts our health, and to begin attending to signs and symptoms of loneliness with preventative measures, the very same way we would do with diet, exercise, and adequate sleep.
Dr. John Cacioppo, PhD, is a Professor of Neuroscience and director of the Center for Cognitive and Social Neuroscience at the University of Chicago, and a leading researcher on the effects on loneliness and human health. According to Dr. Cacioppo, the physical effects of loneliness and social isolation are as real as any other physical detriment to the body — such as thirst, hunger, or pain. “For a social species, to be on the edge of the social perimeter is to be in a dangerous position,” says Dr. Cacioppo, who is the co-author of the best-selling book “Loneliness: Human Nature and the Need for Social Connection”, hailed by critics to be one of the most important books about the human condition to appear in a decade.
Loneliness changes our thoughts, which changes the chemistry of our brains, says Dr. Cacioppo. “The brain goes into a self-preservation state that brings with it a lot of unwanted side effects.” This includes increased levels of cortisol, the stress hormone that can predict heart death due to its highly negative effects on the body. This increase in cortisol triggers a host of negative physical effects — including a persistent disruption in our natural patterns of sleep, according to Dr. Cacioppo. “As a result of increased cortisol, sleep is more likely to be interrupted by micro-awakenings,” reducing our ability to get enough quality sleep, that in time begins to erode our overall greater health and well-being.
One of the most important discoveries of Dr. Cacioppo’s research, is the Epigenetic impacts that loneliness has on our genes. In his recent studies, tests reveal how the emotional and physical impacts of loneliness actually trigger cellular changes that alter the gene expression in our bodies, or “what genes are turned on and off in ways that help prepare the body for assaults, but that also increases the stress and aging on the body as well.” This Epigenetic effect provides important clues in improving our understanding of the physical effects of loneliness, and in an increasingly remote and digitally connected world, minding our digital footprint and ensuring that we cultivate real and meaningful relationships with others may hold the key to keeping us healthy and keeping the onset of loneliness at bay.
Social Media’s Alone Together
Worldwide, there are over 2.01 billion active monthly users of social media, and of the 300 million of us in the United States, sometimes it feels like we’ve all just become new “Friends” on Facebook.
With so many of us being “Friends” and so well connected, you’d think that our social calendars would be totally full.
But the sad truth is that for all of the social media friends that we may have out in cyberspace, studies show that social media usage is actually making us less socially active in the real world, and Americans in particular are finding themselves lonelier than ever.
According to a recent study by sociologists at Duke University and the University of Arizona, published by American Sociological Review, American’s circle of close friends and confidants has shrunk dramatically over the past two decades, and the number who say they have no one outside of their immediate family to discuss important matters with has more than doubled, reaching a shocking 53.4% — up 17% since the dawn of the Internet and social media.
What’s more, nearly a quarter of those surveyed say they have no close friends or confidantes at all — a 14% percent increase since we all became so digitally connected.
Looking at the stats, we should ask ourselves, are digital communication technologies and social media platforms like Facebook and Twitter helping us or actually hurting us?
Many experts seem to feel the latter, and see a clear pattern with social media use and the decline in social intimacy, contributing greatly to today’s social and personal breakdown.
In her recent book “Alone Together: Why We Expect More from Technology and Less from Each Other”, MIT Professor Dr. Sherry Tuckle, PhD argues the case that this just may be so.
Dr. Turkle puts forth a host of pretty convincing signs that technology is threatening to dominate our lives and make us less and less social as humans. In Alone Together, she warns us that in only just a few short years, technology has now become the architect of our intimacies. “Online, we fall prey to the illusion of companionship, gathering thousands of Twitter and Facebook friends, and confusing tweets and wall posts with authentic communication.” But this relentless online digital connection is not at all real social intimacy, and leads us to a deep feeling of solitude.
Compounding matters is the added burden of increasingly busy schedules. People are now working very long hours — far more than in any recent history — and many feel that the only way that they can make social contact is online via social media or even online dating apps — which they often feel is faster and cheaper than actually going out for an intimate connection in person. Many even prefer the limited effort necessary to maintain digital friendships, verses live interpersonal relationships, which allows them to feel connected — but actually still remain somewhat disconnected.
This is perhaps ever more apparent with a new generation of Americans who have grown up with smartphones and social media, and as a result, may have even lost some fundamental social skills due to excessive online and social media use.
Dr. Brian Primack, PhD is the director of the Center for Research on Media, Technology and Health at the University of Pittsburgh, and co-author of a study published by the American Journal of Preventive Medicine, which shows that those who spend the most time digitally connecting on social media — more than two hours a day — had more than twice the odds of feeling socially isolated and lonely, compared to those who spend only a half hour per day. While real life face-to-face social connectedness seems to be strongly associated with feelings of well-being, the study shows that this naturally expected outcome seems to change when our interactions happen virtually. These results seemed very much to be counterintuitive — yet somehow this negative outcome is entirely consistent and true.
Dr. Primack’s earlier research on the connection of social media use and depression in young adults seemed to confirm what many already suspected, that our self-esteem can easily take a nosedive each time we log in to a social media network. There is a natural tendency to compare our lives to those we see online, and when we see others seemingly living the life of our dreams, it’s human nature not to feel just a little bit envious. However, if left unchecked, that envy can quickly turn into low self-esteem — and that can quickly spiral into depression. And like a vicious cycle, the more depressed and the lower our self-esteem, the lonelier we feel.
Meanwhile, a recent study found that those who gave up Facebook for even just a week felt much happier, less lonely and less depressed at the end of the study then other participants who continued using it.
The message is clear, that it’s important to use social media in positive ways. It’s a strong reminder of the importance of establishing real and meaningful interpersonal friendships, versus isolating ourselves in the digital social world. Real life interactions help us to build lasting relationships that fulfill our innate human need to form bonds and feel connected.
The solution, experts say, is that we have to begin to recognize the inherent pitfalls of social media and begin to utilize our online time in more positive ways that enhance our relationships — not detract from them. Social media can actually be a positive step toward building a “Global Village”, if we make it so.
It all depends on how we choose to interact online. It’s important to remember this, in our ever-busy quest for success in our increasingly digitally connected lives.
Connect With Your Friends The Old Fashioned Way — Device Free.
I have established really strong boundaries to have device free outings on date nights, also with my friends or if I am having a business meeting. Let me clarify, a device can be present however it must be switched off completely and preferably out of sight.
I have one friend who I visit sometimes. She is unable or unwilling to hear the boundaries that I would like to have regarding our device free get togethers. She is really smart and quite amazing, we will talk for about 10 minutes and we will be having a delightful deep meaningful conversation, and then like a merciless predator she preys on her phone like she going in for the kill and starts in on her social media. She is an addict. I overtly exit “stage left.” She is disappointed that I leave. This is the only way I can train her with regards to having a device free get together. The lengths of conversation have actually gotten longer since I have been doing that. When we go out for dinner she has to leave her phone at her home otherwise she is unable to help herself to her phone. The question I ask her is, “Dinner with Marina or will it be Dinner with your Phone?” She does opt for Dinner with Marina.
Self Love is one of the most important loves of all. When we learn to love ourselves completely, then we can truly love others
Connect with Your Friends & Loved Ones & Disconnect from Loneliness
01. Choose Self Love & Practice Self Love With Regards To How You Want It To Show Up In Your Life.
02. Choose To Be Worthy & Deserving Of Being Loved By Others On Your Own Terms.
03. Choose To Love People Unconditionally With Strong Boundaries.
04. Choose To Love People Unconditionally Without Being Taken Advantage Of.
05. Choose To Celebrate Who You Are.
06. Choose To See Your Value & How Valuable You Are To Yourself & Others.
07. Choose To Have Self Worth & Self Esteem & Positive Self Deserving In All Areas of Your Life.
08. Choose To Be Empathic With Your Friends With Strong Boundaries.
09. Choose To Be A Great Listener.
10. Choose To Be Worthy & Deserving To Be Listened To & Be Heard.
11. Choose To Be A Good Friend Without Being Taken Advantage Of.
12. Choose To Be Respectful, Present and Mindful With Your Friends.
13. Choose To Speak Your Truth With Emotional Intelligence.
14. Choose To Have Confidence In All Areas of Your Life.
15. Choose To Authentically Live Your Own Personal Truth In All Areas of Your Life.
Fetal development and hormones Edit
The influence of hormones on the developing fetus has been the most influential causal hypothesis of the development of sexual orientation.   In simple terms, the developing fetal brain begins in a "female" typical state. The presence of the Y-chromosome in males prompts the development of testes, which release testosterone, the primary androgen receptor-activating hormone, to masculinize the fetus and fetal brain. This masculinizing effect pushes males towards male typical brain structures, and most of the time, attraction to females. It has been hypothesized that gay men may have been exposed to little testosterone in key regions of the brain, or had different levels of receptivity to its masculinizing effects, or experienced fluctuations at critical times. In women, it is hypothesized that high levels of exposure to testosterone in key regions may increase likelihood of same sex attraction.  Supporting this are studies of the finger digit ratio of the right hand, which is a robust marker of prenatal testosterone exposure. Lesbians on average, have significantly more masculine digit ratios, a finding which has been replicated numerous times in studies cross-culturally.  While direct effects are hard to measure for ethical reasons, animal experiments where scientists manipulate exposure to sex hormones during gestation can also induce lifelong male-typical behavior and mounting in female animals, and female-typical behavior in male animals.    
Maternal immune responses during fetal development are strongly demonstrated as causing male homosexuality and bisexuality.  Research since the 1990s has demonstrated that the more male sons a woman has, there is a higher chance of later born sons being gay. During pregnancy, male cells enter a mother's bloodstream, which are foreign to her immune system. In response, she develops antibodies to neutralize them. These antibodies are then released on future male foetuses and may neutralize Y-linked antigens, which play a role in brain masculinization, leaving areas of the brain responsible for sexual attraction in the female-typical position, or attracted to men. The more sons a mother has will increase the levels of these antibodies, thus creating the observed fraternal birth order effect. Biochemical evidence to support this effect was confirmed in a lab study in 2017, finding that mothers with a gay son, particularly those with older brothers, had heightened levels of antibodies to the NLGN4Y Y-protein than mothers with heterosexual sons.   J. Michael Bailey has described maternal immune responses as "causal" of male homosexuality.  This effect is estimated to account for between 15 and 29% of gay men, while other gay and bisexual men are thought to owe sexual orientation to genetic and hormonal interactions.  
Socialization theories, which were dominant in the 1900s, favored the idea that children were born "undifferentiated" and were socialized into gender roles and sexual orientation. This led to medical experiments in which newborn and infant boys were surgically reassigned into girls after accidents such as botched circumcisions. These males were then reared and raised as females without telling the boys, which, contrary to expectations, did not make them feminine nor attracted to men. All published cases providing sexual orientation grew up to be strongly attracted to women. The failure of these experiments demonstrate that socialization effects does not induce feminine type behavior in males, nor make them attracted to men, and that the organizational effects of hormones on the fetal brain prior to birth have permanent effects. These are indicative of 'nature', not nurture, at least with regards to male sexual orientation. 
The sexually dimorphic nucleus of the preoptic area (SDN-POA) is a key region of the brain which differs between males and females in humans and a number of mammals (e.g., sheep/rams, mice, rats), and is caused by sex differences in hormone exposure.   The INAH-3 region is bigger in males than in females, and is thought to be a critical region in sexual behavior. Dissection studies found that gay men had significantly smaller sized INAH-3 than heterosexual males, which is shifted in the female typical direction, a finding first demonstrated by neuroscientist Simon LeVay, which has been replicated.  Dissection studies are rare, however, due to lack of funding and brain samples. 
Long-term studies of domesticated sheep lead by Charles Roselli have found that 6-8% of rams have a homosexual preference through their life. Dissection of ram brains also found a similar smaller (feminized) structure in homosexually oriented rams compared to heterosexually oriented rams in the equivalent brain region to the human SDN, the ovine sexually dimorphic nucleus (oSDN).  The size of the sheep oSDN has also been demonstrated to be formed in utero, rather than postnatally, underscoring the role of prenatal hormones in masculinization of the brain for sexual attraction.  
Other studies in humans have relied on brain imaging technology, such as research lead by Ivanka Savic which compared hemispheres of the brain. This research found that straight men had right hemispheres 2% larger than the left, described as modest but "highly significant difference" by LeVay. In heterosexual women, the two hemispheres were the same size. In gay men, the two hemispheres were also the same size, or sex atypical, while in lesbians, the right hemispheres were slightly larger than the left, indicating a small shift in the male direction. 
A model proposed by evolutionary geneticist William R. Rice argues that a misexpressed epigenetic modifier of testosterone sensitivity or insensitivity that affected development of the brain can explain homosexuality, and can best explain twin discordance.  Rice et al. propose that these epimarks normally canalize sexual development, preventing intersex conditions in most of the population, but sometimes failing to erase across generations and causing reversed sexual preference.  On grounds of evolutionary plausibility, Gavrilets, Friberg and Rice argue that all mechanisms for exclusive homosexual orientations likely trace back to their epigenetic model.  Testing this hypothesis is possible with current stem cell technology. 
Genetic influences Edit
Multiple genes have been found to play a role in sexual orientation. Scientists caution that many people misconstrue the meanings of genetic and environmental.  Environmental influence does not automatically imply that the social environment influences or contributes to the development of sexual orientation. Hypotheses for the impact of the post-natal social environment on sexual orientation are weak, especially for males.  There is, however, a vast non-social environment that is non-genetic yet still biological, such as prenatal development, that likely helps shape sexual orientation.  : 76
Twin studies Edit
A number of twin studies have attempted to compare the relative importance of genetics and environment in the determination of sexual orientation. In a 1991 study, Bailey and Pillard conducted a study of male twins recruited from "homophile publications", and found that 52% of monozygotic (MZ) brothers (of whom 59 were questioned) and 22% of the dizygotic (DZ) twins were concordant for homosexuality.  'MZ' indicates identical twins with the same sets of genes and 'DZ' indicates fraternal twins where genes are mixed to an extent similar to that of non-twin siblings. In a study of 61 pairs of twins, researchers found among their mostly male subjects a concordance rate for homosexuality of 66% among monozygotic twins and a 30% one among dizygotic twins.  In 2000, Bailey, Dunne and Martin studied a larger sample of 4,901 Australian twins but reported less than half the level of concordance.  They found 20% concordance in the male identical or MZ twins and 24% concordance for the female identical or MZ twins. Self reported zygosity, sexual attraction, fantasy and behaviours were assessed by questionnaire and zygosity was serologically checked when in doubt. Other researchers support biological causes for both men and women's sexual orientation. 
A 2008 study of all adult twins in Sweden (more than 7,600 twins)  found that same-sex behaviour was explained by both heritable genetic factors and unique environmental factors (which can include the prenatal environment during gestation, exposure to illness in early life, peer groups not shared with a twin, etc.), although a twin study cannot identify which factor is at play. Influences of the shared environment (influences including the family environment, rearing, shared peer groups, culture and societal views, and sharing the same school and community) had no effect for men, and a weak effect for women. This is consistent with the common finding that parenting and culture appears to play no role in male sexual orientation, but may play some small role in women. The study concludes that genetic influences on any lifetime same-sex partner were stronger for men than women, and that "it has been suggested individual differences in heterosexual and homosexual behavior result from unique environmental factors such as prenatal exposure to sex hormones, progressive maternal immunization to sex-specific proteins, or neurodevelopmental factors", although does not rule out other variables. The use of all adult twins in Sweden was designed to address the criticism of volunteer studies, in which a potential bias towards participation by gay twins may influence the results:
Biometric modeling revealed that, in men, genetic effects explained .34–.39 of the variance [of sexual orientation], the shared environment .00, and the individual-specific environment .61–.66 of the variance. Corresponding estimates among women were .18–.19 for genetic factors, .16–.17 for shared environmental, and .64–.66 for unique environmental factors. Although wide confidence intervals suggest cautious interpretation, the results are consistent with moderate, primarily genetic, familial effects, and moderate to large effects of the nonshared environment (social and biological) on same-sex sexual behavior. 
Chromosome linkage studies Edit
Chromosome linkage studies of sexual orientation have indicated the presence of multiple contributing genetic factors throughout the genome. In 1993, Dean Hamer and colleagues published findings from a linkage analysis of a sample of 76 gay brothers and their families.  Hamer et al. found that the gay men had more gay male uncles and cousins on the maternal side of the family than on the paternal side. Gay brothers who showed this maternal pedigree were then tested for X chromosome linkage, using twenty-two markers on the X chromosome to test for similar alleles. In another finding, thirty-three of the forty sibling pairs tested were found to have similar alleles in the distal region of Xq28, which was significantly higher than the expected rates of 50% for fraternal brothers. This was popularly dubbed the "gay gene" in the media, causing significant controversy. Sanders et al. in 1998 reported on their similar study, in which they found that 13% of uncles of gay brothers on the maternal side were homosexual, compared with 6% on the paternal side. 
A later analysis by Hu et al. replicated and refined the earlier findings. This study revealed that 67% of gay brothers in a new saturated sample shared a marker on the X chromosome at Xq28.  Two other studies (Bailey et al., 1999 McKnight and Malcolm, 2000) failed to find a preponderance of gay relatives in the maternal line of homosexual men.  One study by Rice et al. in 1999 failed to replicate the Xq28 linkage results.  Meta-analysis of all available linkage data indicates a significant link to Xq28, but also indicates that additional genes must be present to account for the full heritability of sexual orientation. 
Mustanski et al. (2005) performed a full-genome scan (instead of just an X chromosome scan) on individuals and families previously reported on in Hamer et al. (1993) and Hu et al. (1995), as well as additional new subjects. In the full sample they did not find linkage to Xq28. 
Results from the first large, comprehensive multi-center genetic linkage study of male sexual orientation were reported by an independent group of researchers at the American Society of Human Genetics in 2012.  The study population included 409 independent pairs of gay brothers, who were analyzed with over 300,000 single-nucleotide polymorphism markers. The data strongly replicated Hamer's Xq28 findings as determined by both two-point and multipoint (MERLIN) LOD score mapping. Significant linkage was also detected in the pericentromeric region of chromosome 8, overlapping with one of the regions detected in the Hamer lab's previous genomewide study. The authors concluded that "our findings, taken in context with previous work, suggest that genetic variation in each of these regions contributes to development of the important psychological trait of male sexual orientation". Female sexual orientation does not seem to be linked to Xq28,   though it does appear moderately heritable. 
In addition to sex chromosomal contribution, a potential autosomal genetic contribution to the development of homosexual orientation has also been suggested. In a study population composed of more than 7000 participants, Ellis et al. (2008) found a statistically significant difference in the frequency of blood type A between homosexuals and heterosexuals. They also found that "unusually high" proportions of homosexual males and homosexual females were Rh negative in comparison to heterosexuals. As both blood type and Rh factor are genetically inherited traits controlled by alleles located on chromosome 9 and chromosome 1 respectively, the study indicates a potential link between genes on autosomes and homosexuality.  
The biology of sexual orientation has been studied in detail in several animal model systems. In the common fruit fly Drosophila melanogaster, the complete pathway of sexual differentiation of the brain and the behaviors it controls is well established in both males and females, providing a concise model of biologically controlled courtship.  In mammals, a group of geneticists at the Korea Advanced Institute of Science and Technology bred a female mice specifically lacking a particular gene related to sexual behavior. Without the gene, the mice exhibited masculine sexual behavior and attraction toward urine of other female mice. Those mice who retained the gene fucose mutarotase (FucM) were attracted to male mice. 
In interviews to the press, researchers have pointed that the evidence of genetic influences should not be equated with genetic determinism. According to Dean Hamer and Michael Bailey, genetic aspects are only one of the multiple causes of homosexuality.  
In 2017, Scientific Reports published an article with a genome wide association study on male sexual orientation. The research consisted of 1,077 homosexual men and 1,231 heterosexual men. A gene named SLITRK6 on chromosome 13 was identified.  The research supports another study which had been done by the neuroscientist Simon LeVay. LeVay's research suggested that the hypothalamus of gay men is different from straight men.  The SLITRK6 is active in the mid-brain where the hypothalamus is. The researchers found that the thyroid stimulating hormone receptor (TSHR) on chromosome 14 shows sequence differences between gay and straight men.  Graves' disease is associated with TSHR abnormalities, with previous research indicating that Graves' disease is more common in gay men than in straight men.  Research indicated that gay people have lower body weight than straight people. It had been suggested that the overactive TSHR hormone lowered body weight in gay people, though this remains unproven.  
In 2018, Ganna et al. performed another genome-wide association study on sexual orientation of men and women with data from 26,890 people who had at least one same-sex partner and 450,939 controls. The data in the study was meta-analyzed and obtained from the UK Biobank study and 23andMe. The researchers identified four variants more common in people who reported at least one same-sex experience on chromosomes 7, 11, 12, and 15. The variants on chromosomes 11 and 15 were specific to men, with the variant on chromosome 11 located in an olfactory gene and the variant on chromosome 15 having previously been linked to male-pattern baldness. The four variants were also correlated with mood and mental health disorders major depressive disorder and schizophrenia in men and women, and bipolar disorder in women. However, none of the four variants could reliably predict sexual orientation. 
In August 2019, a genome-wide association study of 493,001 individuals concluded that hundreds or thousands of genetic variants underlie homosexual behavior in both sexes, with 5 variants in particular being significantly associated. Some of these variants had sex-specific effects, and two of these variants suggested links to biological pathways that involve sex hormone regulation and olfaction. All the variants together captured between 8 and 25% of the variation in individual differences in homosexual behavior. These genes partly overlap with those for several other traits, including openness to experience and risk-taking behavior. Additional analyses suggested that sexual behavior, attraction, identity, and fantasies are influenced by a similar set of genetic variants. They also found that the genetic effects that differentiate heterosexual from homosexual behavior are not the same as those that differ among nonheterosexuals with lower versus higher proportions of same-sex partners, which suggests that there is no single continuum from heterosexual to homosexual preference, as suggested by the Kinsey scale. 
Epigenetics studies Edit
A study suggests linkage between a mother's genetic make-up and homosexuality of her sons. Women have two X chromosomes, one of which is "switched off". The inactivation of the X chromosome occurs randomly throughout the embryo, resulting in cells that are mosaic with respect to which chromosome is active. In some cases though, it appears that this switching off can occur in a non-random fashion. Bocklandt et al. (2006) reported that, in mothers of homosexual men, the number of women with extreme skewing of X chromosome inactivation is significantly higher than in mothers without gay sons. 13% of mothers with one gay son, and 23% of mothers with two gay sons, showed extreme skewing, compared to 4% of mothers without gay sons. 
Birth order Edit
Blanchard and Klassen (1997) reported that each additional older brother increases the odds of a man being gay by 33%.   This is now "one of the most reliable epidemiological variables ever identified in the study of sexual orientation".  To explain this finding, it has been proposed that male fetuses provoke a maternal immune reaction that becomes stronger with each successive male fetus. This maternal immunization hypothesis (MIH) begins when cells from a male fetus enter the mother's circulation during pregnancy or while giving birth.  Male fetuses produce H-Y antigens which are "almost certainly involved in the sexual differentiation of vertebrates". These Y-linked proteins would not be recognized in the mother's immune system because she is female, causing her to develop antibodies which would travel through the placental barrier into the fetal compartment. From here, the anti-male bodies would then cross the blood/brain barrier (BBB) of the developing fetal brain, altering sex-dimorphic brain structures relative to sexual orientation, increasing the likelihood that the exposed son will be more attracted to men than women.  It is this antigen which maternal H-Y antibodies are proposed to both react to and 'remember'. Successive male fetuses are then attacked by H-Y antibodies which somehow decrease the ability of H-Y antigens to perform their usual function in brain masculinization. 
In 2017, researchers discovered a biological mechanism of gay people who tend to have older brothers. They think Neuroligin 4 Y-linked protein is responsible for a later son being gay. They found that women had significantly higher anti-NLGN4Y levels than men. In addition, mothers of gay sons, particularly those with older brothers, had significantly higher anti-NLGN4Y levels than did the control samples of women, including mothers of heterosexual sons. The results suggest an association between a maternal immune response to NLGN4Y and subsequent sexual orientation in male offspring. 
The fraternal birth order effect, however, does not apply to instances where a firstborn is homosexual.  
Female fertility Edit
In 2004, Italian researchers conducted a study of about 4,600 people who were the relatives of 98 homosexual and 100 heterosexual men. Female relatives of the homosexual men tended to have more offspring than those of the heterosexual men. Female relatives of the homosexual men on their mother's side tended to have more offspring than those on the father's side. The researchers concluded that there was genetic material being passed down on the X chromosome which both promotes fertility in the mother and homosexuality in her male offspring. The connections discovered would explain about 20% of the cases studied, indicating that this is a highly significant but not the sole genetic factor determining sexual orientation.  
Pheromone studies Edit
Research conducted in Sweden  has suggested that gay and straight men respond differently to two odors that are believed to be involved in sexual arousal. The research showed that when both heterosexual women and gay men are exposed to a testosterone derivative found in men's sweat, a region in the hypothalamus is activated. Heterosexual men, on the other hand, have a similar response to an estrogen-like compound found in women's urine.  The conclusion is that sexual attraction, whether same-sex or opposite-sex oriented, operates similarly on a biological level. Researchers have suggested that this possibility could be further explored by studying young subjects to see if similar responses in the hypothalamus are found and then correlating these data with adult sexual orientation. [ citation needed ]
Studies of brain structure Edit
A number of sections of the brain have been reported to be sexually dimorphic that is, they vary between men and women. There have also been reports of variations in brain structure corresponding to sexual orientation. In 1990, Dick Swaab and Michel A. Hofman reported a difference in the size of the suprachiasmatic nucleus between homosexual and heterosexual men.  In 1992, Allen and Gorski reported a difference related to sexual orientation in the size of the anterior commissure,  but this research was refuted by numerous studies, one of which found that the entirety of the variation was caused by a single outlier.   
Research on the physiologic differences between male and female brains are based on the idea that people have male or a female brain, and this mirrors the behavioral differences between the two sexes. Some researchers state that solid scientific support for this is lacking. Although consistent differences have been identified, including the size of the brain and of specific brain regions, male and female brains are very similar.  
Sexually dimorphic nuclei in the anterior hypothalamus Edit
LeVay also conducted some of these early researches. He studied four groups of neurons in the hypothalamus called INAH1, INAH2, INAH3 and INAH4. This was a relevant area of the brain to study, because of evidence that it played a role in the regulation of sexual behaviour in animals, and because INAH2 and INAH3 had previously been reported to differ in size between men and women. 
He obtained brains from 41 deceased hospital patients. The subjects were classified into three groups. The first group comprised 19 gay men who had died of AIDS-related illnesses. The second group comprised 16 men whose sexual orientation was unknown, but whom the researchers presumed to be heterosexual. Six of these men had died of AIDS-related illnesses. The third group was of six women whom the researchers presumed to be heterosexual. One of the women had died of an AIDS-related illness. 
The HIV-positive people in the presumably heterosexual patient groups were all identified from medical records as either intravenous drug abusers or recipients of blood transfusions. Two of the men who identified as heterosexual specifically denied ever engaging in a homosexual sex act. The records of the remaining heterosexual subjects contained no information about their sexual orientation they were assumed to have been primarily or exclusively heterosexual "on the basis of the numerical preponderance of heterosexual men in the population". 
LeVay found no evidence for a difference between the groups in the size of INAH1, INAH2 or INAH4. However, the INAH3 group appeared to be twice as big in the heterosexual male group as in the gay male group the difference was highly significant, and remained significant when only the six AIDS patients were included in the heterosexual group. The size of INAH3 in the homosexual men's brains was comparable to the size of INAH3 in the heterosexual women's brains. [ citation needed ]
William Byne and colleagues attempted to identify the size differences reported in INAH 1–4 by replicating the experiment using brain sample from other subjects: 14 HIV-positive homosexual males, 34 presumed heterosexual males (10 HIV-positive), and 34 presumed heterosexual females (9 HIV-positive). The researchers found a significant difference in INAH3 size between heterosexual men and heterosexual women. The INAH3 size of the homosexual men was apparently smaller than that of the heterosexual men, and larger than that of the heterosexual women, though neither difference quite reached statistical significance. 
Byne and colleagues also weighed and counted numbers of neurons in INAH3 tests not carried out by LeVay. The results for INAH3 weight were similar to those for INAH3 size that is, the INAH3 weight for the heterosexual male brains was significantly larger than for the heterosexual female brains, while the results for the gay male group were between those of the other two groups but not quite significantly different from either. The neuron count also found a male-female difference in INAH3, but found no trend related to sexual orientation. 
LeVay has said that Byne replicated his work, but that he employed a two-tailed statistical analysis, which is typically reserved for when no previous findings had employed the difference. LeVay has said that "given that my study had already reported a INAH3 to be smaller in gay men, a one tailed approach would have been more appropriate, and it would have yielded a significant difference [between heterosexual and homosexual men]".  : 110
J. Michael Bailey has criticized LeVay's critics – describing the claim that the INAH-3 difference could be attributable to AIDS as "aggravating", since the "INAH-3 did not differ between the brains of straight men who died of AIDS and those who did not have the disease".  : 120 Bailey has further criticized the second objection that was raised, that being gay might have somehow caused the difference in INAH-3, and not vice-versa, saying "the problem with this idea is that the hypothalamus appears to develop early. Not a single expert I have ever asked about LeVay's study thought it was plausible that sexual behavior caused the INAH-3 differences."  : 120
The SCN of homosexual males has been demonstrated to be larger (both the volume and the number of neurons are twice as many as in heterosexual males). These areas of the hypothalamus have not yet been explored in homosexual females nor bisexual males nor females. Although the functional implications of such findings still have not been examined in detail, they cast serious doubt over the widely accepted Dörner hypothesis that homosexual males have a "female hypothalamus" and that the key mechanism of differentiating the "male brain from originally female brain" is the epigenetic influence of testosterone during prenatal development. 
A 2010 study by Garcia-Falgueras and Swaab stated that "the fetal brain develops during the intrauterine period in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge. In this way, our gender identity (the conviction of belonging to the male or female gender) and sexual orientation are programmed or organized into our brain structures when we are still in the womb. There is no indication that social environment after birth has an effect on gender identity or sexual orientation." 
Ovine model Edit
The domestic ram is used as an experimental model to study early programming of the neural mechanisms which underlie homosexuality, developing from the observation that approximately 8% of domestic rams are sexually attracted to other rams (male-oriented) when compared to the majority of rams which are female-oriented. In many species, a prominent feature of sexual differentiation is the presence of a sexually dimorphic nucleus (SDN) in the preoptic hypothalamus, which is larger in males than in females.
Roselli et al. discovered an ovine SDN (oSDN) in the preoptic hypothalamus that is smaller in male-oriented rams than in female-oriented rams, but similar in size to the oSDN of females. Neurons of the oSDN show aromatase expression which is also smaller in male-oriented rams versus female-oriented rams, suggesting that sexual orientation is neurologically hard-wired and may be influenced by hormones. However, results failed to associate the role of neural aromatase in the sexual differentiation of brain and behavior in the sheep, due to the lack of defeminization of adult sexual partner preference or oSDN volume as a result of aromatase activity in the brain of the fetuses during the critical period. Having said this, it is more likely that oSDN morphology and homosexuality may be programmed through an androgen receptor that does not involve aromatisation. Most of the data suggests that homosexual rams, like female-oriented rams, are masculinized and defeminized with respect to mounting, receptivity, and gonadotrophin secretion, but are not defeminized for sexual partner preferences, also suggesting that such behaviors may be programmed differently. Although the exact function of the oSDN is not fully known, its volume, length, and cell number seem to correlate with sexual orientation, and a dimorphism in its volume and of cells could bias the processing cues involved in partner selection. More research is needed in order to understand the requirements and timing of the development of the oSDN and how prenatal programming effects the expression of mate choice in adulthood. 
Childhood gender nonconformity Edit
Childhood gender nonconformity, or behaving like the other sex, is a strong predictor of adult sexual orientation that has been consistently replicated in research, and is thought to be strong evidence of a biological difference between heterosexual and non-heterosexuals. A review authored by J. Michael Bailey states: "childhood gender nonconformity comprises the following phenomena among boys: cross-dressing, desiring to have long hair, playing with dolls, disliking competitive sports and rough play, preferring girls as playmates, exhibiting elevated separation anxiety, and desiring to be—or believing that one is—a girl. In girls, gender nonconformity comprises dressing like and playing with boys, showing interest in competitive sports and rough play, lacking interest in conventionally female toys such as dolls and makeup, and desiring to be a boy". This gender nonconformist behavior typically emerges at preschool age, although is often evident as early as age 2. Children are only considered gender nonconforming if they persistently engage in a variety of these behaviors, as opposed to engaging in a behavior on a few times or on occasion. It is also not a one-dimensional trait, but rather has varying degrees. 
Children who grow up to be non-heterosexual were, on average, substantially more gender nonconforming in childhood. This is confirmed in both retrospective studies where homosexuals, bisexuals and heterosexuals are asked about their gender typical behavior in childhood, and in prospective studies, where highly gender nonconforming children are followed from childhood into adulthood to find out their sexual orientation. A review of retrospective studies that measured gender nonconforming traits estimated that 89% of homosexual men exceeded heterosexual males level of gender nonconformity, whereas just 2% of heterosexual men exceeded the homosexual median. For female sexual orientation, the figures were 81% and 12% respectively. A variety of other assessments such as childhood home videos, photos and reports of parents also confirm this finding.  Critics of this research see this as confirming stereotypes however, no study has ever demonstrated that this research has exaggerated childhood gender nonconformity. J. Michael Bailey argues that gay men often deny that they were gender nonconforming in childhood because they may have been bullied or maltreated by peers and parents for it, and because they often do not find femininity attractive in other gay males and thus would not want to acknowledge it in themselves.  Additional research in Western cultures and non-Western cultures including Latin America, Asia, Polynesia, and the Middle East supports the validity of childhood gender nonconformity as a predictor of adult non-heterosexuality. 
This research does not mean that all non-heterosexuals were gender nonconforming, but rather indicates that long before sexual attraction is known, non-heterosexuals, on average, are noticeably different from other children. There is little evidence that gender nonconforming children have been encouraged or taught to behave that way rather, childhood gender nonconformity typically emerges despite conventional socialization.  Medical experiments in which infant boys were sex reassigned and reared as girls did not make them feminine nor attracted to males. 
Boys who were surgically reassigned female Edit
Between the 1960s and 2000, many newborn and infant boys were surgically reassigned as females if they were born with malformed penises, or if they lost their penises in accidents.  : 72–73 Many surgeons believed such males would be happier being socially and surgically reassigned female. In all seven published cases that have provided sexual orientation information, the subjects grew up to be attracted to females. Six cases were exclusively attracted to females, with one case 'predominantly' attracted to females. In a review article in the journal Psychological Science in the Public Interest, six researchers including J. Michael Bailey state this establishes a strong case that male sexual orientation is partly established before birth:
This is the result we would expect if male sexual orientation were entirely due to nature, and it is opposite of the result expected if it were due to nurture, in which case we would expect that none of these individuals would be predominantly attracted to women. They show how difficult it is to derail the development of male sexual orientation by psychosocial means.
They further argue that this raises questions about the significance of the social environment on sexual orientation, stating, "If one cannot reliably make a male human become attracted to other males by cutting off his penis in infancy and rearing him as a girl, then what other psychosocial intervention could plausibly have that effect?" It is further stated that neither cloacal exstrophy (resulting in a malformed penis), nor surgical accidents, are associated with abnormalities of prenatal androgens, thus, the brains of these individuals were male-organized at birth. Six of the seven identified as heterosexual males at follow up, despite being surgically altered and reared as females, with researchers adding: "available evidence indicates that in such instances, parents are deeply committed to raising these children as girls and in as gender-typical a manner as possible." Bailey et al. describe these sex reassignments as 'the near-perfect quasi-experiment' in measuring the impact of 'nature' versus 'nurture' with regards to male homosexuality. 
'Exotic becomes erotic' theory Edit
Daryl Bem, a social psychologist at Cornell University, has theorized that the influence of biological factors on sexual orientation may be mediated by experiences in childhood. A child's temperament predisposes the child to prefer certain activities over others. Because of their temperament, which is influenced by biological variables such as genetic factors, some children will be attracted to activities that are commonly enjoyed by other children of the same gender. Others will prefer activities that are typical of another gender. This will make a gender-conforming child feel different from opposite-gender children, while gender-nonconforming children will feel different from children of their own gender. According to Bem, this feeling of difference will evoke psychological arousal when the child is near members of the gender which it considers as being 'different'. Bem theorizes that this psychological arousal will later be transformed into sexual arousal: children will become sexually attracted to the gender which they see as different ("exotic"). This proposal is known as the "exotic becomes erotic" theory.  Wetherell et al. state that Bem "does not intend his model as an absolute prescription for all individuals, but rather as a modal or average explanation." 
Two critiques of Bem's theory in the journal Psychological Review concluded that "studies cited by Bem and additional research show that [the] Exotic Becomes Erotic theory is not supported by scientific evidence."  Bem was criticized for relying on a non-random sample of gay men from the 1970s (rather than collecting new data) and for drawing conclusions that appear to contradict the original data. An "examination of the original data showed virtually all respondents were familiar with children of both sexes", and that only 9% of gay men said that "none or only a few" of their friends were male, and most gay men (74%) reported having "an especially close friend of the same sex" during grade school.  Further, "71% of gay men reported feeling different from other boys, but so did 38% of heterosexual men. The difference for gay men is larger, but still indicates that feeling different from same-sex peers was common for heterosexual men." Bem also acknowledged that gay men were more likely to have older brothers (the fraternal birth order effect), which appeared to contradict an unfamiliarity with males. Bem cited cross-cultural studies which also "appear to contradict the EBE theory assertion", such as the Sambia tribe in Papua New Guinea, which ritually enforced homosexual acts among teenagers yet once these boys reached adulthood, only a small proportion of men continued to engage in homosexual behaviour - similar to levels observed in the United States.  Additionally, Bem's model could be interpreted as implying that if one could change a child's behavior, one could change their sexual orientation, but most psychologists doubt this would be possible. 
Neuroscientist Simon LeVay said that while Bem's theory was arranged in a "believable temporal order",  : 65 that it ultimately "lacks empirical support".  : 164 Social psychologist Justin Lehmiller stated that Bem's theory has received praise "for the way it seamlessly links biological and environmental influences" and that there "is also some support for the model in the sense that childhood gender nonconformity is indeed one of the strongest predicators of adult homosexuality", but that the validity of the model "has been questioned on numerous grounds and scientists have largely rejected it." 
Sexual practices that significantly reduce the frequency of heterosexual intercourse also significantly decrease the chances of successful reproduction, and for this reason, they would appear to be maladaptive in an evolutionary context following a simple Darwinian model (competition amongst individuals) of natural selection—on the assumption that homosexuality would reduce this frequency. Several theories have been advanced to explain this contradiction, and new experimental evidence has demonstrated their feasibility. 
Some scholars  have suggested that homosexuality is indirectly adaptive, by conferring a reproductive advantage in a non-obvious way on heterosexual siblings or their children, a hypothesised instance of kin selection. By way of analogy, the allele (a particular version of a gene) which causes sickle-cell anemia when two copies are present, also confers resistance to malaria with a lesser form of anemia when one copy is present (this is called heterozygous advantage). 
Brendan Zietsch of the Queensland Institute of Medical Research proposes the alternative theory that men exhibiting female traits become more attractive to females and are thus more likely to mate, provided the genes involved do not drive them to complete rejection of heterosexuality. 
In a 2008 study, its authors stated that "There is considerable evidence that human sexual orientation is genetically influenced, so it is not known how homosexuality, which tends to lower reproductive success, is maintained in the population at a relatively high frequency." They hypothesized that "while genes predisposing to homosexuality reduce homosexuals' reproductive success, they may confer some advantage in heterosexuals who carry them". Their results suggested that "genes predisposing to homosexuality may confer a mating advantage in heterosexuals, which could help explain the evolution and maintenance of homosexuality in the population".  However, in the same study, the authors noted that "nongenetic alternative explanations cannot be ruled out" as a reason for the heterosexual in the homosexual-heterosexual twin pair having more partners, specifically citing "social pressure on the other twin to act in a more heterosexual way" (and thus seek out a greater number of sexual partners) as an example of one alternative explanation. The study acknowledges that a large number of sexual partners may not lead to greater reproductive success, specifically noting there is an "absence of evidence relating the number of sexual partners and actual reproductive success, either in the present or in our evolutionary past". 
The heterosexual advantage hypothesis was given strong support by the 2004 Italian study demonstrating increased fecundity in the female matrilineal relatives of gay men.   As originally pointed out by Hamer,  even a modest increase in reproductive capacity in females carrying a "gay gene" could easily account for its maintenance at high levels in the population. 
Gay uncle hypothesis Edit
The "gay uncle hypothesis" posits that people who themselves do not have children may nonetheless increase the prevalence of their family's genes in future generations by providing resources (e.g., food, supervision, defense, shelter) to the offspring of their closest relatives. 
This hypothesis is an extension of the theory of kin selection, which was originally developed to explain apparent altruistic acts which seemed to be maladaptive. The initial concept was suggested by J. B. S. Haldane in 1932 and later elaborated by many others including John Maynard Smith, W. D. Hamilton and Mary Jane West-Eberhard.  This concept was also used to explain the patterns of certain social insects where most of the members are non-reproductive.
Vasey and VanderLaan (2010) tested the theory on the Pacific island of Samoa, where they studied women, straight men, and the fa'afafine, men who prefer other men as sexual partners and are accepted within the culture as a distinct third gender category. Vasey and VanderLaan found that the fa'afafine said they were significantly more willing to help kin, yet much less interested in helping children who are not family, providing the first evidence to support the kin selection hypothesis.  
The hypothesis is consistent with other studies on homosexuality, which show that it is more prevalent amongst both siblings and twins.  
Vasey and VanderLaan (2011) provides evidence that if an adaptively designed avuncular male androphilic phenotype exists and its development is contingent on a particular social environment, then a collectivistic cultural context is insufficient, in and of itself, for the expression of such a phenotype. 
Some studies have found correlations between physiology of people and their sexuality these studies provide evidence which suggests that:
- Gay men and straight women have, on average, equally proportioned brain hemispheres. Lesbian women and straight men have, on average, slightly larger right brain hemispheres. 
- The suprachiasmatic nucleus of the hypothalamus was found by Swaab and Hopffman to be larger in gay men than in non-gay men  the suprachiasmatic nucleus is also known to be larger in men than in women. 
- Gay men report, on average, slightly longer and thicker penises than non-gay men. 
- The average size of the INAH 3 in the brains of gay men is approximately the same size as INAH 3 in women, which is significantly smaller, and the cells more densely packed, than in heterosexual men's brains. 
- The anterior commissure is larger in women than men and was reported to be larger in gay men than in non-gay men,  but a subsequent study found no such difference. 
- The functioning of the inner ear and the central auditory system in lesbians and bisexual women are more like the functional properties found in men than in non-gay women (the researchers argued this finding was consistent with the prenatal hormonal theory of sexual orientation). 
- The startle response (eyeblink following a loud sound) is similarly masculinized in lesbians and bisexual women. 
- Gay and non-gay people's brains respond differently to two putative sex pheromones (AND, found in male armpit secretions, and EST, found in female urine). 
- The amygdala, a region of the brain, is more active in gay men than non-gay men when exposed to sexually arousing material.  between the index and ring fingers have been reported to differ, on average, between non-gay and lesbian women. 
- Gay men and lesbians are significantly more likely to be left-handed or ambidextrous than non-gay men and women  Simon LeVay argues that because "[h]and preference is observable before birth.  [t]he observation of increased non-right-handness in gay people is therefore consistent with the idea that sexual orientation is influenced by prenatal processes," perhaps heredity. 
- A study of over 50 gay men found that about 23% had counterclockwise hair whorl, as opposed to 8% in the general population. This may correlate with left-handedness. 
- Gay men have increased ridge density in the fingerprints on their left thumbs and little fingers. 
- Length of limbs and hands of gay men is smaller compared to height than the general population, but only among white men. 
J. Michael Bailey has argued that the early childhood gender nonconforming behavior of homosexuals, as opposed to biological markers, are better evidence of homosexuality being an inborn trait. He argues that gay men are "punished much more than rewarded" for their childhood gender nonconformity, and that such behavior "emerges with no encouragement, and despite opposition", making it "the sine qua non of innateness". 
Whether genetic or other physiological determinants form the basis of sexual orientation is a highly politicized issue. The Advocate, a U.S. gay and lesbian newsmagazine, reported in 1996 that 61% of its readers believed that "it would mostly help gay and lesbian rights if homosexuality were found to be biologically determined".  A cross-national study in the United States, the Philippines, and Sweden found that those who believed that "homosexuals are born that way" held significantly more positive attitudes toward homosexuality than those who believed that "homosexuals choose to be that way" or "learn to be that way".  
Equal protection analysis in U.S. law determines when government requirements create a “suspect classification" of groups and therefore eligible for heightened scrutiny based on several factors, one of which is immutability. 
Evidence that sexual orientation is biologically determined (and therefore perhaps immutable in the legal sense) would strengthen the legal case for heightened scrutiny of laws discriminating on that basis.   
The perceived causes of sexual orientation have a significant bearing on the status of sexual minorities in the eyes of social conservatives. The Family Research Council, a conservative Christian think tank in Washington, D.C., argues in the book Getting It Straight that finding people are born gay "would advance the idea that sexual orientation is an innate characteristic, like race that homosexuals, like African-Americans, should be legally protected against 'discrimination' and that disapproval of homosexuality should be as socially stigmatized as racism. However, it is not true." On the other hand, some social conservatives such as Reverend Robert Schenck have argued that people can accept any scientific evidence while still morally opposing homosexuality.  National Organization for Marriage board member and fiction writer Orson Scott Card has supported biological research on homosexuality, writing that "our scientific efforts in regard to homosexuality should be to identify genetic and uterine causes. so that the incidence of this dysfunction can be minimized. [However, this should not be seen] as an attack on homosexuals, a desire to 'commit genocide' against the homosexual community. There is no 'cure' for homosexuality because it is not a disease. There are, however, different ways of living with homosexual desires." 
Some advocates for the rights of sexual minorities resist what they perceive as attempts to pathologise or medicalise 'deviant' sexuality, and choose to fight for acceptance in a moral or social realm.  The journalist Chandler Burr has stated that "[s]ome, recalling earlier psychiatric "treatments" for homosexuality, discern in the biological quest the seeds of genocide. They conjure up the specter of the surgical or chemical "rewiring" of gay people, or of abortions of fetal homosexuals who have been hunted down in the womb."  LeVay has said in response to letters from gays and lesbians making such criticisms that the research "has contributed to the status of gay people in society". 
Scientists at Tokyo Institute of Technology (Tokyo Tech) have set out to harness the potential of self-assembling peptides (SAPs) in intracellular spaces. They present a de novo designed peptide, Y15, which displays a strong .
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'Dragon man' fossil may replace Neanderthals as our closest relative
A near-perfectly preserved ancient human fossil known as the Harbin cranium sits in the Geoscience Museum in Hebei GEO University. The largest of known Homo skulls, scientists now say this skull represents a newly discovered .
SARS-CoV-2 virus can find alternate route to infect cells
Early in the COVID-19 pandemic, scientists identified how SARS-CoV-2, the virus that causes COVID-19, gets inside cells to cause infection. All current COVID-19 vaccines and antibody-based therapeutics were designed to disrupt .
Studies reveal key process needed for cells to recover from stress
St. Jude Children's Research Hospital scientists are studying the processes that enable cells to respond and adapt to environmental stress, many of which are also associated with neurodegenerative diseases. In complementary .
Structural changes in the SARS-CoV-2 Alpha and Beta variants identified
New SARS-CoV-2 variants are spreading rapidly, and there are fears that current COVID-19 vaccines won't protect against them. The latest in a series of structural studies of the SARS-CoV-2 variants' "spike" protein, led by .
Molecular & Computational biology
How density governs receptor activation on immune cells
Scientists from within the Antibody and Vaccine Group at the University of Southampton have gained novel insights into how an important class of immune receptors called tumor necrosis factor receptors (TNFR) are activated.
Molecular & Computational biology
Scientists develop the first CRISPR/Cas9-based gene drive in plants
With a goal of breeding resilient crops that are better able to withstand drought and disease, University of California San Diego scientists have developed the first CRISPR-Cas9-based gene drive in plants.
MeCP2: A binding protein that prevents DNA from being wrapped up in nucleosomes
A team of researchers working at the Institute of Genetics and Molecular and Cellular Biology in Illkirch, France, has found that the MeCP2 protein binds to DNA in a way that prevents it from being wrapped up in nucleosomes. .
What termites and cells have in common
Nature is full of fascinating patterns. Plants show beautiful spiral growth, regularly arranged leaves and petals, animals impress us with their striped and dotted furs and social insects build complex nest structures. These .
Putting functional proteins in their place
Scientists have organized proteins—nature's most versatile building blocks—in desired 2D and 3D ordered arrays while maintaining their structural stability and biological activity. They built these designer functional .
A simple idea to ease conservation costs: Transferring funds
Around the world, nature conservation is not always easy for local governments.
AI used to predict unknown links between viruses and mammals
A new University of Liverpool study could help scientists mitigate the future spread of zoonotic and livestock diseases caused by existing viruses.
A feral past could help chart the future for Brassica vegetables
You might not envision plant scientists as the modern-day Indiana Jones of biology, but University of Missouri researchers have been hot on the hunt for an evolutionary history, looking for clues to the ancestors of our gardens .
Rare giant barking deer spotted in Cambodia
A critically endangered giant barking deer has been spotted in Cambodia for the first time, in a boost for the country's wildlife preservation efforts, officials said Friday.
Invasive Japanese seaweed threatens French Mediterranean coast
A potentially toxic seaweed originally found off Japan has colonised a stretch of the Mediterranean coast near Marseille that is home to one of France's most popular natural attractions.
With remarkable similarities to MS, a disease in dogs opens new avenues for study
The canine disease granulomatous meningoencephalomyelitis (GME), the most common neuroinflammatory disease that affects dogs, shares key features of its pathology and immunology with multiple sclerosis (MS), according to .
Definition of Biology
Biology is the study of life and organisms. This natural science includes the origin, evolution, function, structure and distribution of living organisms. The discipline also concerns itself with topics like the classification of organisms, an organism’s ability to regulate its internal environment, how structures function as a whole, and the interaction of living organisms within an environment. Basic biological concepts include the study of cells as basic structural units of life, genetics and heredity, and transformation of energy by organisms while growing, developing and adapting to their environments.
The Science of Kindness: Biology Proves How We Are All Connected
In my exploration of how kindness connects people, it has become pretty clear to me that being kind to someone else uplifts both people and creates a positive link between them. Many times, I have read how people feel good after they help someone through volunteering, or even holding a door open—and I’ve felt it myself.
If persuaded to explain why it feels good, it is clear that helping someone else (or simply witnessing kindness) sets off a series of changes in the brain similarly to the release of endorphins, the internal opiates. Spiritually, of course, helping someone is the right thing to do. The biological connection between my spiritual understanding and how I feel suggests that nature has wired me to do so my body is reinforcing/rewarding these “right things” with pleasurable sensations. Similarly, the receiver also feels good because he or she has been acknowledged or valued.
Acts of kindness therefore create meaningful connections between people. It is part of what I have called the “kindness-connection cycle”, in which acts of kindness connect the giver and receiver to one another.
The focus of this class is the last arc of the kindness-connection cycle, which states that meaningful connection increases kindness in turn. The central idea is that when we truly understand how each of our lives is intertwined with so many others, kindness, compassion, and collaboration flow much more naturally.
Although we are unique individuals, our lives are part of a dynamic and vibrant larger network. What each of us does in that network influences many others and vice versa—i.e., we are in this together.
There are many different examples of how we are connected to each other, such as being connected through economics, interpersonal interactions, workplace, community, family, etc.
One overlooked aspect of being connected to each other, however, is the common biology that we share. For example, blood courses through our arteries and veins before being filtered by the kidneys and pumped by a heart which beats approximately 100,000 times every day.
There are many other systems that, with slight variation, function the same way in healthy people, such as the regulation of blood sugar, blood pressure, and immune responses – and although we may differ in outward appearance (height, body, facial shape, or skin color), our bodies still generally work the same way.
Beyond the systems that we have in common, we also actively share our biological lives with each other. Let’s focus on oxygen, one of the most abundant elements on the planet that is absolutely critical for our survival. Inhaled oxygen (O2) is required to use calories and convert them into energy fuel for our cells this process then produces carbon dioxide (CO2) which we exhale as a byproduct. Life is not possible without oxygen.
Let’s imagine that you and I are hiking a trail in the woods and we stop to admire a vista. Much of the oxygen we are inhaling is probably produced by the trees and plant life—yet how did the tree make oxygen? As other hikers have gone through the forest, the trees—powered by sunlight—absorb the carbon dioxide that is exhaled by the hikers so they can transform it into cellulose. O2 is then released from the CO2 that the trees have absorbed, thus continuing the oxygen cycle between the hikers and the trees.
This means that the oxygen I breathe in to survive was used by someone else in the past to help them live as well—and it will also be used by someone else in the future.
As oxygen is constantly being recycled, and each person needs about 500 liters of oxygen each day, multiple authors have speculated on how we may have inhaled the same oxygen molecules as Julius Caesar, Abraham Lincoln, Martin Luther King, Jr., or any other historical figure.
The bottom line: all of our lives depend on sharing, and this sharing extends across time.
This example also illustrates how we are critically connected to trees and nature. Without plant life, oxygen wouldn’t be produced and carbon dioxide wouldn’t be cleared—and since roughly half of the oxygen on Earth comes from phytoplankton in the oceans, this means that our oxygen-dependent lives are also tied to the sea. Phytoplankton, in turn, depend on waste and motion from larger sea creatures—such as whales.
When something disrupts these cycles, like deforestation or whale hunting, we share in the problems that follow. When we protect and nourish them, however, we honor their significance and are rewarded for it.
What goes around, comes around. Life is much more about cycles rather than straight lines. Oxygen is just one of many examples that, by the nature of our shared biology, we are connected to one another. The same is true for nitrogen, water, iron, and a host of other biologically essential factors that are recycled by other life forms. This gets more complex once we include the interactions of insects and animals that are necessary to keep the fabric of our interwoven network healthy and vibrant.
So what does this teach us? It tells us that our lives are more intimately connected than we might ever have thought. On a basic level, it teaches that sharing (kindness and cooperation) is actively required for living beings to survive.
Beyond that, we are deeply connected by the oxygen cycle in a reciprocating, cooperative way. Without trees and greenery, we would not survive—and as those systems depend on carbon dioxide to survive, we sustain them in turn. Short-sighted selfishness that overuses or abuses a component of the cycle will come back around to affect us.
But the cycle is fragile without us doing the right thing to responsibly maintain our part of a mutually nourishing cycle, it can fail. Doing the right thing honors two principles: being kind to and respecting the roles of other members of the cycle, and being kind to ourselves to sustain our own well being.
The eminent conservationist John Muir wrote: “When one tugs at a single thing in nature, you find it attached to the rest of the world.” That is, we are all connected.
Interested in learning more about the science of kindness and its role in your life? Visit EnvisionKindness.org to learn more.
Be Sure And Share This Inspiring Segment Of “The Science Of Kindness” With Your Friends On Social Media – Photo by Gabriela Palai, CC
Jobs for biological sciences majors
What can you do with a major in biology? Marquette's biology graduates have found success and leadership roles in:
- Academic and hospital research
- Environmental science
- Food industries
- Forensic science
- Government agencies (FBI, FDA, DNR, NASA, USDA)
- Graduate school
- Physical therapy
- Physician assistant
- Public health
- Science writing or journalism
- Veterinary medicine
- Wildlife management
Recent employers of Marquette biology majors include:
- Abbott Laboratories
- BloodCenter of Wisconsin
- Bristol-Myers Squibb
- Centers for Disease Control and Prevention
- Dana Farber Cancer Institute
- Eli Lilly
- GE Healthcare
- Medical College of Wisconsin
- USDA Forest Products Laboratory
Marquette biology majors have gone on to graduate school at:
- Case Western Reserve University
- Columbia University
- Georgia State
- Harvard Medical School
- Loyola University Medical School
- Marquette University
- Mayo Clinic
- Medical College of Wisconsin
- Stony Brook University (SUNY) Medical Center
- Tufts University
- University of California, Berkeley
- University of California, Irvine
- University of Cincinnati
- University of Michigan
- University of Minnesota
- University of Pittsburgh School of Medicine
- University of Wisconsin–Madison Medical School
Biological link between stress, anxiety and depression identified
Scientists at The University of Western Ontario have discovered the biological link between stress, anxiety and depression. By identifying the connecting mechanism in the brain, this high impact research led by Stephen Ferguson of Robarts Research Institute shows exactly how stress and anxiety could lead to depression. The study also reveals a small molecule inhibitor developed by Ferguson, which may provide a new and better way to treat anxiety, depression and other related disorders.
The findings are published online in the journal Nature Neuroscience.
Ferguson, Ana Magalhaes and their colleagues used a behavioural mouse model and a series of molecular experiments to reveal the connection pathway and to test the new inhibitor. "Our findings suggest there may be an entire new generation drugs and drug targets that can be used to selectively target depression, and therefore treat it more effectively, " says Ferguson, the director of the Molecular Brain Research Group at Robarts, and a professor in the Department of Physiology & Pharmacology at Western's Schulich School of Medicine & Dentistry. "We've gone from mechanism to mouse, and the next step is to see whether or not we can take the inhibitor we developed, and turn it into a pharmaceutical agent."
The research was conducted in collaboration with Hymie Anisman at Carleton University, and funded through the Canadian Institutes of Health Research (CIHR). "According to the World Health Organization, depression, anxiety and other related mood disorders now share the dubious distinction of being the most prevalent causes of chronic illness," says Anthony Phillips, the scientific director of the CIHR Institute of Neurosciences, Mental Health and Addiction. "Using the power of molecular biology, Stephen Ferguson and colleagues provide novel insights that may be the key to improving the lives of so many individuals coping with these forms of mental ill health."
The linking mechanism in the study involves the interaction between corticotropin releasing factor receptor 1 (CRFR1) and specific types of serotonin receptors (5-HTRs). While no one has been able to connect these two receptors on a molecular level, the study reveals that CRFR1 works to increase the number of 5-HTRs on cell surfaces in the brain, which can cause abnormal brain signaling. Since CRFR1 activation leads to anxiety in response to stress, and 5-HTRs lead to depression, the research shows how stress, anxiety and depression pathways connect through distinct processes in the brain. Most importantly, the inhibitor developed by the Ferguson lab blocks 5-HTRs in the pathway to combat anxious behaviour, and potentially depression, in mice.
While major depressive disorder often occurs together with anxiety disorder in patients, the causes for both are strongly linked to stressful experiences. Stressful experiences can also make the symptoms of anxiety and depression more severe. By discovering and then blocking a pathway responsible for the link between stress, anxiety and depression, Ferguson not only provides the first biological evidence for a connection, but he also pioneers the development of a potential drug for more effective treatment.
Materials provided by University of Western Ontario. Note: Content may be edited for style and length.
Examples of Physical Changes
Remember, the appearance of matter changes in a physical change, but its chemical identity remains the same.
- Crushing a can
- Mixing sand and water
- Breaking a glass
- Dissolving sugar and water
- Shredding paper
- Chopping wood
- Mixing red and green marbles
- Sublimation of dry ice
- Crumpling a paper bag
- Melting solid sulfur into liquid sulfur. This is an interesting example since the state change does cause a color change, even though the chemical composition is the same before and after the change. Several nonmetals, such as oxygen and radon, change color as they change phase.
- Chopping an apple
- Mixing salt and sand
- Filling a candy bowl with different candies
- Vaporizing liquid nitrogen
- Mixing flour, salt, and sugar
- Mixing water and oil