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Updated Answer: Science marches on. The latest research now shows that not only did the Dinosaurs die out as a result of impact, but impacts have also been shown to have caused several other major extinction events. This is incredibly important, because after Raup, D. M. & Sepkoski, J. J. (1982) argued that most if not all mass extinctions were caused by impacts, there was a lot of skepticism, since impact evidence for most of them was lacking, and the most severe extinction event, the end Permian still seems to have been the result of severe vulcanism. Now, however, evidence of impacts seems to correspond to many extinction events, not just the K-T impact that apparently exterminated the last of the Dinosaurs.Recent studies have shown that not just the Cretaceous-Palaeogene Extinction (Chicxulub impactor), but also the Cryogenian ~800m years ago; the Great Ordovician Biodiversification Event (470 ~ 480m years ago); and the Late Triassic extinction Event, 201 m years ago) were caused by impacts. At least it has been presented in major new studies of impacts, some of which are incredibly ingenious sampling of craters on the Moon.From Nature:Asteroid shower on the Earth-Moon system immediately before the Cryogenian period revealed by KAGUYA (Lunar orbiter)AbstractMeteoroid bombardment of the Earth-Moon system must have caused catastrophic damage to the terrestrial ecosphere. However, ancient meteoroid impacts and their relations to environmental changes are not well understood because of erosion and/or resurfacing processes on Earth. Here, we investigate the formation ages of 59 lunar craters with fresh morphologies and diameters greater than approximately 20 km and first find that 8 of 59 craters were formed simultaneously. Considering the radiometric ages of ejecta from Copernicus crater and impact glass spherules from various Apollo landing sites, we conclude that sporadic meteoroid bombardment occurred across the whole Moon at approximately 800 Ma. Based on crater scaling laws and collision probabilities with the Earth and Moon, we suggest that at least (4–5) × 10kg of meteoroids, approximately 30–60 times more than the Chicxulub impact, must have plunged into the Earth-Moon system immediately before the Cryogenian, which was an era of great environmental changes.IntroductionUnderstanding meteoroid bombardment of the Earth system is an issue of both great scientific interest and practical importance because impacts are potentially hazardous to the Earth. Since the 541 Ma Cambrian biodiversity explosion, mass extinction events have occurred at least five times (the so-called Big five events) (Raup, D. M. & Sepkoski, J. J. Mass extinctions in the marine fossil record. Science 215, 1501–1503 (1982)), and extra-terrestrial impacts are considered a potential cause of some of them (e.g., Late Triassic (Onoue, T. et al. Bolide impact triggered the Late Triassic extinction event in equatorial Panthalassa. Sci. Rep. 6, 29609 (2016)), and Cretaceous-Palaeogene extinctions (Schulte, P. et al. The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary. Science 327, 1214–1218 (2010)), competing with the flood basalt eruption-related hypotheses.After the first discovery of fossil L-chondrites in Ordovician limestones in Sweden (Richards, M. A. et al. Triggering of the largest Deccan eruptions by the Chicxulub impact. GSA Bull. 127, 1507–1520 (2015)), abundant L-chondrites, meteorite-tracing chromite grains and iridium enrichment have been found in Sweden, England, Scotland, China, and Russia in rocks whose stratigraphic ages are 470 ~ 480 million years (Ma) (Wilde, P. et al. Iridium abundances across the Ordovician-Silurian stratotype. Science 233, 339–341 (1986)) (Schmitz, B., Häggström, T. & Tassinari, M. Sediment-dispersed extraterrestrial chromite traces a major asteroid disruption event. Science 300, 961–964 (2003))Moreover, several large terrestrial craters in the Northern Hemisphere have been found to have radiometric ages of approximately 430 ~ 470 Ma. Further, approximately two-thirds of ordinary L-chondrites are known to be heavily shocked and degassed, withAr–Ar ages near 470 Ma. Therefore, it is generally considered that the L-chondrite parent body suffered a major impact approximately 470 million years ago and was catastrophically disrupted, causing a very large meteoroid shower on Earth for several million years. Recently, Schmitz et al suggested that the extraordinary amounts of dust during >2 Myr cooled the Earth and triggered Ordovician icehouse conditions, sea-level fall, and major faunal turnovers related to the Great Ordovician Biodiversification Event. However, to date, other ancient meteoroid impacts and their relations to environmental changes have not been well understood because of erosion and/or resurfacing processes on Earth.Paleontologists have never liked the impact theory because it relies upon evidence that is way outside their field of expertise (iridium anomalies, fullerenes, impact melt, and orbital dynamics of inter-planetary comets). They have been fighting against accepting it for years now and have presented all kinds of evidence for vulcanism as the culprit.“The Nastiest Feud in ScienceA Princeton geologist has endured decades of ridicule for arguing that the fifth extinction was caused not by an asteroid but by a series of colossal volcanic eruptions. But she’s reopened that debate.”However, we know for certain the following:There was an impact. The Chixlulub Crater was found. It is about 180 miles in diameter, about the right size for the predicted impactor - as estimated from the Iridium Anomaly. (It would have been a problem for the theory if the crater did not match up with the predicted size of the impactor as estimated from Iridium Anomaly — although if it were too small, one might conclude the impactor broke up into several pieces and we only happened to discover one impact site). As it happens, the Chicxulub impact site and the predicted size match up pretty well.Artist’s image of what the crater looked like millions of years after impact, but before it was buried under miles of later sedimentary layers.2. About 1/2 of the worlds’ forests burned down. We know that because geologists found the evidence in the form of fossilized soot particles in the K-T Boundary Layer along with impact melt glass, etc.3. Physicists can estimate the size of the impactor from the iridium anomaly - iridium is an extremely rare element in the earths’ crust, but common in meteorites and comets left over from the formation of the Solar System. Calculating the amount of iridium spread out over the earth’s surface gives a rough estimate of the size of the impactor since they know how much % iridium would be in a typical meteorite or comet.4. The estimated size of the impactor, the size of the crater, the predicted effects from an impact that size, all match up.So, those paleontologists who still resist the impact arguments essentially boil down to this:“The dinosaurs all died of natural causes from vulcanism shortly (a few hundred thousand years) before a giant meteor hit and incinerated 1/2 the world’s forests, and caused global darkness for months or years, followed by devastating global warming.”Imagine that you were a coroner and you learned that at exactly midnight a burglar broke into an old lady’s house, strangled, shot and stabbed her, and then burned the house down. Would you believe that she had accidentally died of natural causes (a heart attack) 1 minute before midnight and the burglars just strangled, shot and stabbed her corpse? Would you return a verdict of death by natural causes?No.That’s what some paleontologists would still have you believe. Nobody will be able to prove that the dinosaurs all died as a result of the impact unless someone finds a dinosaur that was fossilized who lived at exactly the same time as the extinction event. That is extremely unlikely.So, maybe they were all dead and the impact just happened to incinerate their corpses. But, that would be the wildest coincidence in the history of the Earth. Personally, I don’t buy it, but I suppose scientists will continue to investigate and come up with theories.

‘What are the other prebiotic foods to best feed the gut microbes?’There is more hype than substance to claims that something or the other is a prebiotic that best sustains healthy gut microbiota since the latter itself lacks universal definition, is far from generalizable, and is largely the product of genetics, diet, lifestyle, age and gender, to name just a few of the most important factors. In fact, as recently as 2011 the European Food Safety Authority - Wikipedia (EFSA) stated (1, emphasis mine),'based on current scientific knowledge, it is not possible to define the exact numbers of the different microbial groups which constitute a normal microbiota. The evidence available to the Panel does not establish that increasing the number of any groups of microorganisms, including lactobacilli and/or bifidobacteria, is in itself a beneficial physiological effect. For function claims related to changes in gastro-intestinal microbiota these changes should be accompanied by a beneficial physiological or clinical outcome.'No wonder there is even less clarity with regard to Prebiotic (nutrition) - Wikipedia, compounds indigestible by human gut epithelial cells but digestible by specific bacteria. Especially pertinent since the major marketing claim for most commercial products touting prebiotic benefits is their capacity to support 'healthy intestinal microflora'.How Prebiotics Might Help Sustain Beneficial Gut Microbes: Some Data And Unresolved IssuesGut microbes digest prebiotics, increasing the rate of their metabolic products such as lactic acid and other fermentation products. These in turn reduce local gut lumen pH and encourage the growth of other microbes capable of utilizing such fermentation products and so on. Over time, this process builds a network of mutually interdependent microbial species but its potential to change the entire gut ecosystem starts with the initial human cell-indigestible component(s), i.e., prebiotic. However, causal relationships between prebiotic-driven microbiota changes and health effects still remain speculative and unproven. That definition of prebiotics keeps changing only serves to emphasize their study is nascent.For example, Glenn R. Gibson and Marcel B. Roberfroid originally defined prebiotics in 1995 as (2),'a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health’Modified in 2004 (3) to'A prebiotic is a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microbiota that confers benefits upon host wellbeing and health’And modified yet again in 2010 (4) to'selectively fermented ingredients that result in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health'Such frequent definition changes engender confusion among consumers, prevent uniform, comparable scientific studies from being pursued, and prevent consensus formation between scientists, regulators, food industry and healthcare professionals (5).The type of effects we should expect from prebiotics also remain unclear:Increase in some specific bacteria, say, Faecalibacterium prausnitzii or bifidobacteria or lactic acid bacteria or just increase in bacterial diversity? Is increase in bacterial diversity a generalizable health benefit?Increase in a specific output, say, fermentation or Short-chain fatty acid - Wikipedia (SCFA) or many other effects also possible?Which is more important, dose or frequency?How equivalent are natural prebiotics versus supplements? Are their effects even comparable?What about effect on immune function? Is it direct or indirect, by selectively binding and eliminating pathogens, i.e., Colonisation resistance - Wikipedia?Don’t responses varying between individuals preclude generalization?Different people respond differently to the same prebiotic (6, 7).Specifically Inulin - Wikipedia didn't uniformly increase gut bifidobacteria in all those who took them, with levels staying low in some who started out with low numbers (6).Response to prebiotics is also different between healthy and ill people (8) and between those lean versus obese (9).Examples Of Some Substances Commonly Accepted As PrebtioicsCurrently identified prebiotics are carbohydrates though this doesn't preclude other compounds such as proteins from being found to have prebiotic properties in future (8). Human breast milk is a classic prebiotic with substantial evidence of health benefits, specifically promotion of bifidobacteria colonization of infant gut (10, 11). Thus far the most robust list of physiological effects is available for Fructan - Wikipedia (12, also see table below from 13). Other broadly accepted prebiotics are Fructooligosaccharide - Wikipedia (FOS) and Galactooligosaccharide - Wikipedia (GOS).Inulin-type fructans are abundant in chicory root and Jerusalem artichoke (12, 13).Natural FOS are found to varying degree in banana, garlic, honey, onion, wheat (13, 14).Natural GOS are abundant in pulses (Legume - Wikipedia) (12).‘Is collagen hydrolysate/gelatin a prebiotic for your gut microbes?’No. Thus far no proteins have been labeled prebiotic. Obviously, being indigestible and fermentable are criteria unlikely to be fulfilled by most proteins.Collagen is the most abundant structural protein in animals, constituting ~30% of total animal protein (15). Primarily derived from the Collagen in connective tissue, bone and skin, Gelatin is a high molecular weight protein that unfolds when melted and cools into a water-trapping helix-coil structure that forms a reversible gel. Consider Jell-O - Wikipedia, the ever-present dessert. Though it looks solid, it's actually >99% liquid.While it's been part of our diet for centuries, the industrial revolution made gelatin practically ubiquitous, from foodstuffs to photography (think glossy photo paper) to glues to pharmaceuticals. Being amphoteric (Amphoterism - Wikipedia), having a variable Isoelectric point - Wikipedia as well as capacity for Coacervate - Wikipedia (separation of colloid particles from a solution) makes gelatin ideal for Micro-encapsulation - Wikipedia, hence its ubiquity in industrial food and pharmaceutical products (as capsules, sponges, Excipient - Wikipedia for example). Other advantages include (16)Easily digestible, high quality protein containing neither carbohydrates nor fats.Gluten-free.Extremely low allergenic potential.Clinical studies have shown special types of gelatin, marketed as collagen hydrolysate, can have a protective effect on joint cartilage (15). Hence its wide prevalence as a food additive for osteoarthritis patients and athletes.Could Gelatin Be A Prebiotic? No Evidence Yet To Support Such A Possibility.Though it's ubiquitous in the food industry, no systematic efforts have assessed if gelatin has prebiotic qualities. For example, as recently as 2015-2016, comprehensive reviews on collagen and gelatin list their major potential biological effects as antioxidant, antihypertensive, anticancer, antiphotoaging and cholesterol-lowering (15, 17) with no mention at all of prebiotic capacity.However, neither is this unsurprising since most confirmed prebiotics tend to be poorly digested carbohydrates. Since carbohydrates yield certain defined effects such as fermentation, lactic acid, etc., efforts to identify new prebiotics focus on capacity to do likewise. It's entirely possible such a 'looking under the lamp post approach' may impair uncovering novel classes of prebiotics, which may not generate fermentation products or SCFA and yet be indigestible or primarily digested by gut microbes and have beneficial gut microbe and health effects.Reports of gelatin's direct effect on microbes are meager.Gelatin strongly supports the growth of many microbes (16). This is why extremely stringent ISO9000-compliant quality control procedures are necessary during its industrial-scale manufacture.At least one known Probiotic - Wikipedia, (microbes with proven health benefits), namely, Bacillus clausii - Wikipedia (https://microbewiki.kenyon.edu/index.php/Bacillus_clausii), can hydrolyze Gelatin. A soil bacterium first described in 1995, its probiotic properties are currently the focus of active research (18).A few clinical studies have noted oral Gelatin/Collagen hydrolysate can influence appetite, suppressing it in the short-term (19) but not in the long-term (20), influence weight (21), again not in the long-term (22), and improve skin texture (23, 24, 25, 26). None of these studies have even speculated the observed biological effects could be due to effects on gut microbes.Bottomline, as of 2016 there appear to be no scientific studies that have explicitly, comprehensively and systematically examined if and what effect Gelatin/Collagen hydrolysate have on gut microbiota, let alone explored the possibility they may have prebiotic effects.Bibliography1. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). "Guidance on the scientific requirements for health claims related to gut and immune function." EFSA J. 9 (2011): 1984-95. http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2011.1984/epdf2. Glenn, G. R., and M. B. Roberfroid. "Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics." J. nutr 125 (1995): 1401-1412. https://www.ilri.org/biometrics/Publication/Abstract/Case%20study%2017%20-1.pdf3. Gibson, Glenn R., et al. "Dietary modulation of the human colonic microbiota: updating the concept of prebiotics." Nutrition research reviews 17.02 (2004): 259-275.4. Gibson, Glenn R., et al. "Dietary prebiotics: current status and new definition." Food Sci Technol Bull Funct Foods 7 (2010): 1-19. https://www.researchgate.net/profile/Nathalie_Delzenne2/publication/228840917_Dietary_prebiotics_Current_status_and_new_definition/links/0fcfd508653e1f101b000000.pdf5. Hutkins, Robert W., et al. "Prebiotics: why definitions matter." Current opinion in biotechnology 37 (2016): 1-7. http://isappscience.org/wp-content/uploads/2016/03/hutkins-why-definitions-matter-prebiotics-ISAPP-15.pdf6. Ramirez-Farias, Carlett, et al. "Effect of inulin on the human gut microbiota: stimulation of Bifidobacterium adolescentis and Faecalibacterium prausnitzii." British Journal of Nutrition 101.04 (2009): 541-550. https://www.researchgate.net/profile/Alan_Duncan3/publication/5262190_Effect_of_inulin_on_the_human_gut_microbiota_stimulation_of_Bifidobacterium_adolescentis_and_Faecalibacterium_prausnitzii/links/00b49535d2b023c2d1000000.pdf7. Louis, Petra, et al. "Diversity of human colonic butyrate‐producing bacteria revealed by analysis of the butyryl‐CoA: acetate CoA‐transferase gene." Environmental microbiology 12.2 (2010): 304-314. https://www.researchgate.net/profile/Harry_Flint/publication/26874831_Diversity_of_human_colonic_butyrate-producing_bacteria_revealed_by_analysis_of_the_butyryl-CoAacetate-CoA_transferase/links/0c960519b8b374c4aa000000.pdf8. Whelan, Kevin. "Mechanisms and effectiveness of prebiotics in modifying the gastrointestinal microbiota for the management of digestive disorders." Proceedings of the Nutrition Society 72.03 (2013): 288-298. https://www.cambridge.org/core/services/aop-cambridge-core/content/view/474C06973251BB448DA8C1DB647F7377/S0029665113001262a.pdf/mechanisms-and-effectiveness-of-prebiotics-in-modifying-the-gastrointestinal-microbiota-for-the-management-of-digestive-disorders.pdf9. Aguirre, Marisol, Carlota Bussolo de Souza, and Koen Venema. "The gut microbiota from lean and obese subjects contribute differently to the fermentation of arabinogalactan and inulin." PloS one 11.7 (2016): e0159236. http://journals.plos.org/plosone/article/asset?id=10.1371/journal.pone.0159236.PDF10. Mueller, Noel T., et al. "The infant microbiome development: mom matters." Trends in molecular medicine 21.2 (2015): 109-117. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4464665/pdf/nihms695563.pdf11. Chichlowski, Maciej, et al. "Bifidobacteria isolated from infants and cultured on human milk oligosaccharides affect intestinal epithelial function." Journal of pediatric gastroenterology and nutrition 55.3 (2012): 321. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3381975/pdf/nihms363696.pdf12. Louis, Petra, Harry J. Flint, and Catherine Michel. "How to Manipulate the Microbiota: Prebiotics." Microbiota of the Human Body. Springer International Publishing, 2016. 119-142. Microbiota of the Human Body13. Schaafsma, Gertjan, and Joanne L. Slavin. "Significance of inulin fructans in the human diet." Comprehensive Reviews in Food Science and Food Safety 14.1 (2015): 37-47. https://www.researchgate.net/profile/Gertjan_Schaafsma/publication/269418716_Significance_of_Inulin_Fructans_in_the_Human_Diet/links/54e10f8f0cf2953c22b99e10.pdf14. Belorkar, Seema A., and A. K. Gupta. "Oligosaccharides: a boon from nature’s desk." AMB Express 6.1 (2016): 82. Oligosaccharides: a boon from nature’s desk15. Liu, Dasong, et al. "Collagen and gelatin." Annual review of food science and technology 6 (2015): 527-557.16. Schrieber, Reinhard, and Herbert Gareis. Gelatine handbook: theory and industrial practice. John Wiley & Sons, 2007. Gelatine Handbook17. Koyama, Y. "Effects of Collagen Ingestion and their Biological Significance." J Nutr Food Sci 6.504 (2016): 2. http://www.omicsonline.org/open-access/effects-of-collagen-ingestion-and-their-biological-significance-2155-9600-1000504.pdf18. Felis, Giovanna E., Franco Dellaglio, and Sandra Torriani. "Taxonomy of probiotic microorganisms." Prebiotics and probiotics science and technology. Springer New York, 2009. 591-637.19. Hochstenbach-Waelen, Ananda, et al. "Single-protein casein and gelatin diets affect energy expenditure similarly but substrate balance and appetite differently in adults." The Journal of nutrition 139.12 (2009): 2285-2292. Single-Protein Casein and Gelatin Diets Affect Energy Expenditure Similarly but Substrate Balance and Appetite Differently in Adults20. Hochstenbach-Waelen, Ananda, et al. "Effects of a supra-sustained gelatin–milk protein diet compared with (supra-) sustained milk protein diets on body-weight loss." British journal of nutrition 105.9 (2011): 1388. https://www.researchgate.net/profile/Stijn_Soenen/publication/49790180_Effects_of_a_supra-sustained_gelatin-milk_protein_diet_compared_with_supra-sustained_milk_protein_diets_on_body-weight_loss/links/0deec532159e232d83000000.pdf21. Rubio, I. G. S., et al. "Oral ingestion of a hydrolyzed gelatin meal in subjects with normal weight and in obese patients: Postprandial effect on circulating gut peptides, glucose and insulin." Eating and Weight Disorders-Studies on Anorexia, Bulimia and Obesity 13.1 (2008): 48-53.22. Hochstenbach-Waelen, A., et al. "No long-term weight maintenance effects of gelatin in a supra-sustained protein diet." Physiology & behavior 101.2 (2010): 237-244.23. Tanaka, Midori, Yoh-ichi Koyama, and Yoshihiro Nomura. "Effects of collagen peptide ingestion on UV-B-induced skin damage." Bioscience, biotechnology, and biochemistry 73.4 (2009): 930-932. http://www.tandfonline.com/doi/pdf/10.1271/bbb.8064924. Proksch, E., et al. "Oral supplementation of specific collagen peptides has beneficial effects on human skin physiology: a double-blind, placebo-controlled study." Skin pharmacology and physiology 27.1 (2013): 47-55. https://www.researchgate.net/profile/Michael_Schunck/publication/255957972_Oral_Supplementation_of_Specific_Collagen_Peptides_Has_Beneficial_Effects_on_Human_Skin_Physiology_A_Double-Blind_Placebo-Controlled_Study/links/542110ff0cf203f155c5fb28.pdf25. Proksch, E., et al. "Oral intake of specific bioactive collagen peptides reduces skin wrinkles and increases dermal matrix synthesis." Skin pharmacology and physiology 27.3 (2013): 113-119.26. Schunck, Michael, et al. "Dietary Supplementation with Specific Collagen Peptides Has a Body Mass Index-Dependent Beneficial Effect on Cellulite Morphology." Journal of medicinal food 18.12 (2015): 1340-1348. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4685482/pdf/jmf.2015.0022.pdfThanks for the R2A, Anonymous.

I am reposting this from a comment that I made to an answer of a similar question.Prior to the 1970’s, gender identity was believed to be a product of social influence. This led to the practice of assigning gender at birth to individuals who were born with indiscriminate sex organs or who were involved in accidents at very young ages, such as botched circumcisions. It was believed that with surgery and hormones any child could be successfully raised any gender. Only after they ruined the lives of these individuals did anyone realize that this was a dangerous and consequential misconception. Since then extensive research has found NO evidence that social factors play a role in our gender identity. Rather, gender identity is a product of our brain sex, which is determined during fetal development. In the mid 1980’s, it was first revealed that there are multiple areas between male and female brains that differ in size and function. We can see a person’s brain sex by looking at certain areas in their brain and this has been done and continues to be done using new brain imaging techniques.A common misconception is that ‘biological sex’ is determined solely by our chromosomes. However, chromosomes are only one of three components that comprise our biological sex, the other two are brain sex and gonadal sex. The components that make up our biological sex are distinct between females and males. Each develop at discrete times during pregnancy and can therefore develop incongruently. Brain sex is arguably the most important aspect of our biological sex, because our brains are who we are. We all begin development with feminine brains and bodies. The degree of masculinization the brain undergoes during development in response to varying hormone levels in the womb determines our gender identity. This variation creates the spectrum of gender identity: a continuum with two ends, one end female and the other male.In most animals, including humans, males and females have different sex chromosomes. During fertilization, each parent donates a copy of one of their two sex chromosomes. Females donate one of their two female chromosomes (XX) while males can either donate their female chromosome (X) or male chromosome (Y). Therefore chromosomal sex is determined by the father. While that may seem like a lot of “power” for the father to have, the effect of hormones released during pregnancy can result in significant modifications of the genetically intended sex. I say “intended” because our DNA is essentially a recipe in which our sex chromosomes are the instructions for making a female or male individual. For instance, I can begin preparing cookies with a particular cookie recipe but if I forget a step, miscalculate a measurement or baking time, or simply decide to alter the recipe, the result won’t fit the specifications of the recipe and the outcome could vary drastically. The same concept applies in the “making” of a baby during pregnancy. Morphologically, all embryos, regardless of DNA, begin with a female brain and body. In other words, female is the “default” sex and all male characteristics are derived from female characteristics. Thus men have nipples, the penis is a masculinized clitoris, the ovaries become testes, and male brain traits diverge from female ones. Sexual differentiation occurs at two distinct periods during development. Reproductive organs and genitalia undergo sexual differentiation during the first 6-12 weeks of pregnancy. In the presence of male chromosomes and the absence of interference, both the mother and fetus will release the appropriate types and amounts of hormones, which will act upon the fetus’s reproductive organs and “masculinize” them. After this and before the sexual differentiation of the brain, the fetus will have a masculinized body and a feminine brain. Sexual development of the brain does not occur until the second trimester of pregnancy when, in the absence of interference, hormones act upon the fetus’s brain to masculinize the appropriate areas. If the fetus’s sex chromosomes are female the masculinization at these distinct time periods should not occur. This interaction of necessary components on vital timelines is what makes the process susceptible to modification.Human development is a complex and delicate process. Different hormones, exposure times, and fetal receptiveness can interfere with sexual development. Chromosomal mutations, stress, kidney dysfunction, hormone treatment, drug use, famine, and vigorous exercise have also been found to affect sexual development. For instance, exposure to either the stress hormone cortisol or female hormones at certain times during development can have masculinizing effects on the fetus. Therefore, if a mother experiences significant stress during one of the vital times of sexual development, a fetus who is genetically female can develop a male brain and or body! In fact, by manipulating hormones during embryonic development Dr. S.M. Breedlove’s lab has produced rats that have the brain of one sex and the genitalia of another. Pollutants, malnutrition, diet, and many other things can affect our production and metabolism of hormones. Several medications when taken during pregnancy have been shown to increase the risk of giving birth to a child with transsexuality, including the miscarriage prevention drug, DES, given to over 2 million women between 1939 and 1960. In addition, prenatal exposure to contaminants, analgesics, pesticides, alcohol and nicotine have all been found to affect sexual development.Transsexuality is not a psychological disorder or an aberrant choice. Transsexuals do not have abnormal brains; they simply have a normal brain sex that differs from their gonadal sex. Some transsexuals enjoy living between both genders and it is likely that they have brains in which some areas were masculinized while others were not. The misbelief that transsexuality is a psychological or social condition phenomenon perpetuates the idea that trans people are different simply because they are confused, were abused or choose to be different. A consequence of such ignorance is a lack of empathy for trans people, and the social acceptance of their ridicule and discrimination. When society understands that this condition is a product of incongruent brain and body anatomy rather than a deviant behavior, trans people will fare far better.One way to minimize harmful social misconceptions is to choose more accurate terminology. The prefix “trans” means across, and “sex”, refers to the biological state of being male or female. Therefore, transsexual means ‘across sexes’, which is the best familiar term currently in use, but is not the most appropriate. Crossing the biological sexes infers going from one side to another, when in fact transsexuals possess facets of both sexes. Among many neuroscientists, transsexuality is more appropriately termed “neuro-anatomic intersexuality” meaning the brain and body anatomy are between the sexes. Gender, refers to the social and cultural states of being male or female. Therefore, the term transgender literally means “across the social and cultural states of being male or female”. Given the biological underpinnings of transsexuality, the term transgender is a misnomer perpetuating the idea that this is a social condition rather than an anatomical one. The term intersexuality, meaning “between sexes”, is the most appropriate familiar term, transsexuality being the most polar form of intersexuality.References:Abé, C., Johansson, E., Allzén, E., Savic, I., 2014. Sexual orientation related differences in cortical thickness in male individuals. PLoS One 9, e114721.Alexander, G.M., Hines, M., 2002. Sex differences in response to children’s toys in nonhuman primates (Cercopithecus aethiops sabaeus). Evol. Hum. Behav. 23, 467–479.Allen, L.S., Gorski, R.A., 1992. Sexual orientation and the size of the anterior commissure in the human brain. Proc. Natl. Acad. Sci. U.S.A. 89, 7199–7202.Auger, A.P., Auger, C.J., 2011. 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