Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases

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By Karl Gruber Birds, fish, and even humans have shattered barriers when it comes to mating rituals, from which partner initiates the courting to which one picks up the check at a fancy restaurant. But things are a bit simpler for frogs, as males and females stick to clearly defined roles: Males serenade the females, and females pick their favorite males to mate. Now, a new study suggests that the smooth guardian frog of Borneo (Limnonectes palavanensis) is an exception to that rule. During the mating season, the female frogs sing to the males in an attempt to win them over—a reversal of the normal process. In fact, if you see a single frog surrounded by a bunch of serenading croakers, called a “lek,” it’s most likely a lucky male being courted by a chorus of females. Males occasionally belt out “advertisement calls” to let females know that they are available. After mating, it’s the males who stay behind to care for the eggs, even taking tadpoles to small ponds after they hatch. This is the first known example of role reversal in singing frogs, scientists write in a recent issue of Behavioral Ecology and Sociobiology. It may even represent the first case of full-blown sex role reversal, which would also require that males do the mate choosing. Researchers are working on that now, but they say that—judging by the high rate of female serenading—males may be the picky ones. © 2017 American Association for the Advancement of Science.

Keyword: Sexual Behavior
Link ID: 23755 - Posted: 06.21.2017

Laurel Hamers When things get hot, embryonic bearded dragon lizards turn female — and now scientists might know why. New analyses, reported online June 14 in Science Advances, reveal that temperature-induced changes in RNA’s protein-making instructions might set off this sex switch. The findings might also apply to other reptile species whose sex is influenced by temperature. Unlike most mammals, many species of reptiles and fish don’t have sex chromosomes. Instead, they develop into males at certain temperatures and females at others. Bearded dragon lizards are an unusual case because chromosome combinations and temperature are known to influence sex determination, says ecologist Clare Holleley of the Commonwealth Scientific and Industrial Research Organisation in Canberra, Australia (SN: 7/25/15, p.7). When eggs are incubated below 32° Celsius, embryonic bearded dragons with two Z chromosomes develop as male, while dragons with a Z and a W chromosome develop as female. But as temperatures creep above 32°, chromosomally male ZZ dragons will reverse course and develop as females instead. “They have two sex chromosomes, but they also have this temperature override,” Holleley says. By comparing bearded dragons that are female because of their chromosomes and those that are female because of environmental influences, Holleley and her colleagues hoped to sort out genetic differences that might point to how the lizards make the switch. The team collected RNA from the brain, reproductive organs and other tissues of normal female, normal male and sex-reversed female Australian central bearded dragons (Pogona vitticeps). Then, the researchers compared that RNA, looking for differences in the ways the lizards were turning on genes. |© Society for Science & the Public 2000 - 2017.

Keyword: Sexual Behavior
Link ID: 23745 - Posted: 06.15.2017

Hannah Devlin Science correspondent “Love looks not with the eyes, but with the mind. And therefore is winged Cupid painted blind,” Shakespeare wrote. Now scientists have pinpointed the specific patterns of brain activity that accompany romance, offering a new explanation for why love sends our judgement haywire. As a relationship takes root, the study found, the brain’s reward circuit goes into overdrive, rapidly increasing the value placed on spending time with one’s love interest. This, at least, was the case in the prairie vole, scientists’ animal model of choice for studying the neuroscience of love. Elizabeth Amadei, who co-led the work at Emory University in Atlanta, said: “As humans, we know the feelings we get when we view images of our romantic partners, but, until now, we haven’t known how the brain’s reward system works to lead to those feelings.” In order to get more direct access to what is happening in the brain, Amadei and colleagues turned to the North American voles, which as a species have almost perfected monogamy. They mate for life, share nest-building duties and have an equal role in raising their young – although, like humans, voles have the occasional “extramarital” fling. Using electrical probes, the scientists recorded directly from the brains of female voles as they encountered a potential partner, mated for the first time and began to show signs of having formed a lifelong bond, indicated by “huddling” behaviour.

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 23692 - Posted: 06.01.2017

By Ariana Eunjung Cha Depression is usually considered an issue parents have to watch out for starting in the turbulent teenage years. The CW channel, full of characters with existential angst about school, friends and young love, tells us so, as do the countless parenting books about the adolescent years in every guidance counselor's office. But what if by that time it's already too late? A large new study out this week contains some alarming data about the state of children's mental health in the United States, finding that depression in many children appears to start as early as age 11. By the time they hit age 17, the analysis found, 13.6 percent of boys and a staggering 36.1 percent of girls have been or are depressed. These numbers are significantly higher than previous estimates. Understanding the risk of depression is critically important because of the close link between depressive episodes and serious issues with school, relationships and suicide. While researchers have long known about the gender gap in depression, with more adult women than men suffering from the condition, the new numbers show that whatever divergent paths boys and girls take happens even earlier than expected. Published in the journal Translational Psychiatry, the study was based on data compiled from in-person interviews with more than 100,000 children who participated in the National Survey of Drug Use and Health from 2009 to 2014. The NSDUH is an annual survey on a representative sample of the U.S. population. Among the standard questions asked are ones about insomnia, irritability, and feelings of guilt or worthlessness that researchers used to “diagnose” survey participants with depression using diagnostic criteria from the Diagnostic and Statistical Manual of Mental Disorders. Through the survey, they were able to capture a broader group of children than those who have a formal diagnosis and who may be in treatment. © 1996-2017 The Washington Post

Keyword: Depression; Development of the Brain
Link ID: 23687 - Posted: 06.01.2017

By STEPH YIN A female and male get together. One thing leads to another, and they have sex. His sperm fuses with her egg, half of his DNA combining with half of her DNA to form an embryo. As humans, this is how we tend to think of reproduction. But there are many other bizarre ways reproduction can take place. For instance, scientists have discovered a fish carrying genes only from its father in the nucleus of its cells. Found in a type of fish called Squalius alburnoides, which normally inhabits rivers in Portugal or Spain, this is the first documented instance in vertebrates of a father producing a near clone of itself through sexual reproduction — a rare phenomenon called androgenesis — the researchers reported in the journal Royal Society Open Science on Wednesday. The possibility of androgenesis is just one of many mysteries about Squalius alburnoides. It’s not a species in the usual sense, but rather something called a hybrid complex, a group of organisms with multiple parental combinations that can mate with one another. The group is thought to have arisen from hybridization between females of one species, Squalius pyrenaicus, and males of another species, now extinct, that belonged to a group of fish called Anaecypris. To sustain its population, Squalius alburnoides mates with several other closely related species belonging to the Squalius lineage. That it can reproduce at all is unusual enough. Most hybrids, like mules, are sterile because the chromosomes from their parents of different species have trouble combining, swapping DNA and dividing — steps required for egg or sperm production. Squalius alburnoides males circumvent this problem by producing sperm cells that do not divide, and therefore contain more than one chromosome set. This is important because most animals, Squalius alburnoides included, need at least two chromosome sets to survive. © 2017 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 23669 - Posted: 05.27.2017

Tonight, our economics correspondent, Paul Solman, explores another potential connection: whether there’s a link between risk-taking in leadership, testosterone and the perceptions around gender. It’s part of his ongoing weekly series, Making Sense, which airs every Thursday. MAN: Welcome, everybody, to this CNBC discussion on the future of banking at the World Economic Forum. PAUL SOLMAN: Financial CEOs at Davos this year. ANDREW LIVERIS, CEO, Dow Chemical: Good morning. Mr. President. Andrew Liveris, Dow Chemical. PAUL SOLMAN: Manufacturing CEOs at the White House. MARK FIELDS, CEO, Ford Motor Company: CEO of Ford. DOUGLAS OBERHELMAN, CEO, Caterpillar: Chairman of Caterpillar. PRESIDENT DONALD TRUMP: Some of the great people in the world of business. PAUL SOLMAN: CEOs now being mentioned as the next president. But, in 2017, the vast majority of CEOs, 96 percent of the Fortune 500, are still men. JENNIFER LERNER, Harvard University: I think that this is socially constructed. The differences between males and females on a wide variety of things are smaller than the differences within males and within females. PAUL SOLMAN: Psychologist Jennifer Lerner studies gender and leadership at Harvard. We will hear more from her in a bit. But, first, let’s check in with economist Andy Kim, who has made a career out of studying CEOs in intriguingly quirky ways. Now, a few of you might remember Andy Kim teaching me two years ago the equestrian dance move in the hyper-viral video sensation “Gangnam Style,” part of his offbeat research showing that CEOs who become visible, for whatever reason, can see their stock price rise irrationally. Well, he presented his brand-new research, not yet published, at this year’s annual Economics Convention. His latest hypothesis is as offbeat as ever. ANDY KIM: There is a strong linkage between your facial masculinity and your risk-taking behavior. PAUL SOLMAN: Kim is now exploring a possible link between CEO risk-taking and the hormone testosterone, which, starting with mid-19th century experiments on roosters, has been linked to male dominance and aggression throughout the animal kingdom. But how do you measure testosterone in CEOs with little time and probably even less inclination to give Korean assistant finance professors blood or saliva samples? One possible way, thought Kim, would be to study their facial bone structure. © 1996 - 2017 NewsHour Productions LLC.

Keyword: Sexual Behavior; Aggression
Link ID: 23663 - Posted: 05.26.2017

James Gorman Darwin’s finches, those little birds in the Galápagos with beaks of different sizes and shapes, were instrumental in the development of the theory of evolution. Similar birds had large and small beaks and beaks in between, all related to what kinds of insects and seeds they ate. From one ancestor, it seemed, different adaptations to the environment had evolved, giving the birds that adapted a survival edge in a particular ecological niche — evolution by natural selection. Biologists who came later went on to identify the genetic changes that had produced different beak shapes. Now another group of finch-like birds has provided a similar example, but of a different kind of evolution, one driven not by the demands of the environment, but by the demands of female birds. Their preferences in color and pattern caused the evolution of different species of seedeater, all with the same behavior and diet, but with males that look different. That’s a process called sexual selection, which Darwin also wrote about. Leonardo Campagna, a researcher at Cornell University and the Cornell Lab of Ornithology, and a group of scientists from the United States and South America investigated nine species of southern capuchino seedeaters, doing full genomes for each one and reported their findings in Science Advances. They found that the DNA of all the species is remarkably similar, as are the birds. All the females look alike and all of the species feed on grass seeds plucked from grass stalks of living plants. Only the males are different. They have a wide variety of colorations and their courting songs are also distinct. Dr. Campagna and the other researchers found that differences between species DNA were all minimal, ranging from as little as 0.03 percent to as great as 0.3 percent. All the species showed variation in the same area, DNA that appeared to have a role in regulating genes for the pigment melanin. © 2017 The New York Times Company

Keyword: Evolution; Sexual Behavior
Link ID: 23660 - Posted: 05.25.2017

Elle Hunt About 150 years ago, and “almost a lifetime” either side, Charles Darwin was beleaguered by the problem of the peacock’s tail. Just the sight of a feather, he wrote in April 1860, “makes me sick!” The plumage of the male bird represented a hole in his theory of evolution. According to Victorian thinking, beauty was divine creation: God had designed the peacock for his own and humankind’s delight. In, On The Origin of Species, published the previous year, Darwin had challenged the dominant theory of creationism, arguing that man had been made not in God’s image but as a result of evolution, with new species formed over generations in response to their environment. But beauty, and a supposed aesthetic sense in animals (“We must suppose [that peahens] admire [the] peacock’s tail, as much as we do,” he wrote), took Darwin the best part of his life to justify – not least because the theory he eventually landed upon went against the grain of his entire worldview. Sexual selection was of strategic importance to Darwin, says Evelleen Richards, an honorary professor in history and philosophy of science at the University of Sydney: it was a naturalistic account for aesthetic differences between male and female animals of the same species, shoring up his defence of natural selection.

Keyword: Evolution; Sexual Behavior
Link ID: 23642 - Posted: 05.22.2017

Susan Milius The supermoms of the mammal world are big, shy redheads. Studying growth layers in orangutan teeth shows that mothers can nurse their youngsters for eight-plus years, a record for wild mammals. Teeth from a museum specimen of a young Bornean orangutan (Pongo pygmaeus) don’t show signs of weaning until 8.1 years of age. And a Sumatran orangutan (P. abelii) was still nursing during the few months before it was killed at 8.8 years, researchers report May 17 in Science Advances. Tests also show that youngsters periodically start to taper off their dependence on their mother’s milk and then, perhaps if solid food grows scarce, go back to what looks like an all-mom diet. Such on-again, off-again nursing cycles aren’t known in other wild mammals, says study coauthor Tanya Smith, an evolutionary anthropologist at Griffith University in Nathan, Australia. Marks of milk drinking Two images of a cross section of a first molar from a 4.5-year-old Bornean orangutan are shown. At left, numbers indicate days from birth (dotted line, starting with 0) when particular spots formed. At right, colors indicate concentrations of barium, which increase (shading toward red) when the youngster depended more on mother’s milk. A greenish swath at the top indicates nursing as an infant that gave way to blue as solid food became part of the diet. Yellow and red streaks indicate repeated times when the youngster again depended mostly on milk for nutrition. oragutan molar |© Society for Science & the Public 2000 - 2017.

Keyword: Sexual Behavior; Development of the Brain
Link ID: 23632 - Posted: 05.18.2017

Nicola Davis Humans can determine a dog’s mood by the sound of its growl, scientists have found, with women showing greater ability than men. While previous studies have found that humans can unpick the context of barks, the latest study investigated whether the same was true of canine grumbles, with some previous research suggesting humans struggle to differentiate between playful and aggressive vocalisations. “It is an important thing that humans are capable [of recognising] the emotional state of another species just based on the vocal characteristics,” said Tamás Faragó, first author of the study from Eötvös Loránd University in Hungary. To tackle the conundrum, Faragó and colleagues used previously captured recordings of 18 dogs growling in three contexts: guarding food from other dogs, playing tug-of-war with humans, and being threatened by the approach of a stranger. The researchers monitored several features, including the length of each growl and its frequency. Two sets of the recordings, which included two growls from each context, were played to 40 adults. Each participant was asked to record their impression of the first set of growls on a sliding scale, rating their perception of the dog for five emotions: fear, aggression, despair, happiness and playfulness. © 2017 Guardian News and Media Limited

Keyword: Animal Communication; Sexual Behavior
Link ID: 23621 - Posted: 05.17.2017

By STEPH YIN In most mammals, us included, biological sex is determined by a lottery between two letters: X and Y, the sex chromosomes. Inherit one X each from mom and dad, and develop ovaries, a womb and a vagina. Inherit an X from mom and a Y from dad, and develop testes and a penis. But there are rare, mysterious exceptions. A small number of rodents have no Y chromosomes, yet are born as either females or males, not hermaphrodites. Now, scientists may be one step closer to figuring out how sex determination works in one of these rodents. In a study published in Science Advances on Friday, Japanese scientists suggested that cells of the endangered Amami spiny rat, from Japan, are sexually flexible and capable of adapting to either ovaries or testes. When the researchers injected stem cells derived from a female rat into male embryos of laboratory mice, the cells developed into and survived as sperm precursors in adult males. The result was surprising since scientists have never been able to generate mature sperm from female stem cells, largely because sperm production normally requires the Y chromosome. Found only in the subtropical forests of an island in Japan called Amami Oshima, Amami spiny rats are threatened by habitat destruction, competition with black rats not native to the island and predation by mongooses and feral cats and dogs. Their range has been reduced to less than 300 square miles, an area smaller than New York City. Both female and male Amami spiny rats have only one X chromosome, an arrangement only known to occur in a handful of rodents among mammals. Arata Honda, associate professor at the University of Miyazaki and the lead author of the paper, said in an email that he was partly motivated to study Amami spiny rats in the hope that learning about them might reduce their risk of extinction. © 2017 The New York Times Company

Keyword: Sexual Behavior
Link ID: 23611 - Posted: 05.13.2017

Amy Maxmen Cells that prune connections between neurons in babies’ brains as they grow are thought to have a role in autism spectrum disorder. Now, a study suggests that the number and behaviour of these cells — called microglia — vary in boys and girls, a finding that could help to explain why many more boys are diagnosed with autism and related disorders. Donna Werling, a neurogeneticist at the University of California, San Francisco, and her colleagues found that genes associated with microglia are more active in male brains than in female brains in the months before birth. “This suggests there is something fundamentally different about male and female brain development,” she says. The research, to be presented on 13 May at the International Meeting for Autism Research in San Francisco, California, is still preliminary. Very little is known about how microglial trimming behaviour affects brain development. But the study by Werling’s team “is the kind of work that makes you say ‘Wow, this is really interesting, and we should take it seriously’”, says Kevin Pelphrey, a neuroscientist at Yale School of Medicine in New Haven, Connecticut. There are two to five times many males with autism as females. Although the disorder — whose cause remains elusive — is widely acknowledged to be underdiagnosed in girls, psychiatrists agree that there is a significant disparity between the numbers of male and female cases. It suggests that biological differences between the sexes are involved. © 2017 Macmillan Publishers Limited,

Keyword: Autism; Glia
Link ID: 23605 - Posted: 05.12.2017

By Alice Klein It is pest control without poison. A new type of bait that stops rats from having babies is helping to tackle infestations in several US cities. The bait – known as ContraPest – was approved by the US Environmental Protection Agency last August. It makes rats infertile by triggering early menopause in females and impairing sperm production in males. There are no side effects and the rats eventually die of natural causes. The technique is considered more benign than other control strategies being investigated, such as gene drive, which can be used to spread infertility genes through pest populations. A recent report by the US National Academies of Sciences warned that gene drive could have unforeseen consequences. The first field trial of ContraPest, conducted in the New York City Subway in 2013, halved the resident rat population in three months. Two more trials have now been completed in the US – one at a large-scale farm and one in an urban area – both in East Coast cities. Rat numbers at the farm fell by one-third over three months. In the urban area, population growth was suppressed during the peak breeding season so that the population expanded at only one-third the expected rate. “You’ll never wipe out rats completely – they’re too smart,” says Brandy Pyzyna from SenesTech, the biotechnology company in Arizona that developed the bait. © Copyright Reed Business Information Ltd.

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 23583 - Posted: 05.06.2017

By Jef Akst Drawing on data on organ-, tissue-, and individual-specific gene expression from the Genotype-Tissue Expression (GTex) Portal, Shmuel Pietrokovski and Moran Gershoni of the Weizmann Institute of Science in Israel developed a comprehensive map of genes that are differentially expressed in men and women. The study was inspired by work the duo conducted several years ago, in which they found that mutations accumulated in genes for sperm formation likely because they were expressed only in men, not in women. As a result, even harmful mutations would only cause problems to half the population; unaffected women would continue to pass on the defective gene without any hit to their fitness. To explore whether other genes expressed differentially between the sexes might be similarly subject to mutation accumulation, Pietrokovski and Gershoni examined some 20,000 protein-coding genes, of which around 6,500 were expressed more in one sex than the other somewhere in the body. And sure enough, selection was effectively weaker in these genes, leading to the pile up of deleterious mutations. “The more a gene was specific to one sex, the less selection we saw on the gene,” Gershoni told the institute’s news publication, Weizmann Wonder Wander, this week (May 3). “The basic genome is nearly the same in all of us, but it is utilized differently across the body and among individuals,” he continued. “Thus, when it comes to the differences between the sexes, we see that evolution often works on the level of gene expression.” © 1986-2017 The Scientist

Keyword: Sexual Behavior
Link ID: 23581 - Posted: 05.06.2017

By RICHARD O. PRUM In a mossy forest in the western Andes of Ecuador, a small, cocoa-brown bird with a red crown sings from a slim perch. Bip-Bip-WANNGG! It sounds like feedback from an elfin electric guitar. Three rival birds call back in rapid response. These male club-winged manakins are showing off to attract female mates. Their strange songs are associated with an even stranger movement. Instead of opening their beaks, they flick their wings open at their sides to make the Bips, and then snap their wings up over their backs to produce the extraordinary WANNGG. They are singing with their wings, and their potential mates seem to find the sound very alluring. This is an evolutionary innovation — a whole new way to sing. But the evolutionary mechanism behind this novelty is not adaptation by natural selection, in which only those who survive pass on their genes, allowing the species to become better adapted to its environment over time. Rather, it is sexual selection by mate choice, in which individuals pass on their genes only if they’re chosen as mates. From the peacock’s tail to the haunting melodies of the wood thrush, mate choice is responsible for much of the beauty in the natural world. Most biologists believe that these mechanisms always work in concert — that sex appeal is the sign of an objectively better mate, one with better genes or in better condition. But the wing songs of the club-winged manakin provide new insights that contradict this conventional wisdom. Instead of ensuring that organisms are on an inexorable path to self-improvement, mate choice can drive a species into what I call maladaptive decadence — a decline in survival and fecundity of the entire species. It may even lead to extinction. © 2017 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 23580 - Posted: 05.06.2017

By Simon Makin The past few decades have seen intensive efforts to find the genetic roots of neurological disorders, from schizophrenia to autism. But the genes singled out so far have provided only sketchy clues. Even the most important genetic risk factors identified for autism, for example, may only account for a few percent of all cases. Much frustration stems from the realization that the key mutations elevating disease risk tend to be rare, because they are less likely to be passed on to offspring. More common mutations confer only small risks (although those risks become more significant when calculated across an entire population). There are several other places to look for the missing burden of risk, and one surprising possible source has recently emerged—an idea that overturns a fundamental tenet of biology and has many researchers excited about a completely new avenue of inquiry. Accepted dogma holds that—although every cell in the body contains its own DNA—the genetic instructions in each cell nucleus are identical. But new research has now proved this assumption wrong. There are actually several sources of spontaneous mutation in somatic (nonsex) cells, resulting in every individual containing a multitude of genomes—a situation researchers term somatic mosaicism. “The idea is something that 10 years ago would have been science fiction,” says biochemist James Eberwine of the University of Pennsylvania. “We were taught that every cell has the same DNA, but that's not true.” There are reasons to think somatic mosaicism may be particularly important in the brain, not least because neural genes are very active. © 2017 Scientific American

Keyword: Development of the Brain; Genes & Behavior
Link ID: 23565 - Posted: 05.04.2017

By Elizabeth Pennisi When, 6 years ago, divers captured on video a cuckolding attempt among squidlike animals called cuttlefish, experts were stunned. “The violence was beyond anything we had ever seen in the laboratory,” says Roger Hanlon, an ecologist at the Marine Biological Laboratory in Woods Hole, Massachusetts, who had been studying captive cuttlefish for years. Now, by carefully analyzing the behavior of the two males involved, he and his colleagues suggest the stepwise escalation of their fight likely required more brainpower than many researchers thought invertebrates had, they report this week in American Naturalist. The video (above) first shows a common European male cuttlefish (Sepia officinalis) mating with a female. While he escorts her to where she will lay her eggs, a second male suddenly appears and chases him away. But the first male doesn’t give up, and as his rival starts to get fresh with the female, the scuffle gets ever more intense. The rivals squirt ink at each other and jet about. Then, their dark markings turn even darker, and they engage in a quick battle of biting, grappling, and cork-screwing that soon sends the intruder scurrying off. Now that the scientists know how such explosive situations come about, they hope to recreate those circumstances in the lab to study male rivalries more systematically. © 2017 American Association for the Advancement of Science. A

Keyword: Aggression; Sexual Behavior
Link ID: 23564 - Posted: 05.04.2017

Jon Brooks Max, age 13, is agender — neither male nor female. When referring to Max, you don't use "he" or "she;" you use "they." Once strictly a pronoun of the plural variety, "they" is now doing double duty as singular, too — referring to individuals, like Max, who do not see gender as an either/or option. (NPR agreed not to use Max's last name, because the family feared the sort of online threats that have been made to other transgender families.) If the whole he/she pronoun thing feels awkward to you, Max is sympathetic — and patient. 'We are seeing more and more kids saying, 'You know what? What's with this either-or business? What's with this boy-girl and you have to fit in one box or the other?' " Diane Ehrensaft, psychologist, Child and Adolescent Gender Center, UCSF Benioff Children's Hospital "I can't expect anyone to use the right pronouns for me because it's not a thing that people know," Max tells me. "It's been great being myself, but it's also been really hard for people to get it, and for even family to get pronouns and stuff." We're talking in Max's room at home, where posters on the wall showcase the teen's love of theater: Peter Pan, Tarzan, The Pirates of Penzance. Max is old enough now to enjoy using make-up — blush, foundation, lipstick — but still young enough to enjoy going with their mom to see "Willy Wonka & The Chocolate Factory." (The review from Max: Gene Wilder's great!) From these surroundings, you wouldn't think the room's occupant is someone who has already poked and prodded at the most fundamental sense of who they are. Really, this is just a kid's room. © 2017 npr

Keyword: Sexual Behavior
Link ID: 23562 - Posted: 05.02.2017

By Abigail Beall You can’t eat, you can’t sleep and all you can think about is your next fix. You may be addicted to love. Intense romance can often come with symptoms resembling addiction – euphoria, craving, dependence, withdrawal and relapse – and brain scans have shown that it can be linked to drug-addiction-like activity in the brain’s reward centres. But the idea that people can be addicted to love is contentious. “It gets complicated because people disagree on the correct theory of addiction, and people especially disagree about what we mean when we use the term ‘love’ ”, says Brian Earp, at the Oxford University Centre for Neuroethics. “I think it is when you realise you do not want to be in love yet cannot avoid it, and it causes bad things, like abuse, that we cross the line into something addiction-like,” says Anders Sandberg, also at the Oxford University Centre for Neuroethics. Now Earp and his team have found evidence that there are in fact two different types of love addiction, after reviewing 64 studies of love and addiction published between 1956 and 2016. They found that people who feel desperately alone when not in a relationship, and try to replace an ex-partner straight away, could have what the team has called a “narrow” form of love addiction.

Keyword: Drug Abuse; Sexual Behavior
Link ID: 23552 - Posted: 04.29.2017

By Debra W. Soh The reasons behind why people are gay, straight, or bisexual have long been a source of public fascination. Indeed, research on the topic of sexual orientation offers a powerful window into understanding human sexuality. The Archives of Sexual Behavior recently published a special edition devoted to research in this area, titled “The Puzzle of Sexual Orientation.” One study, conducted by scientists at the University of Lethbridge in Alberta, Canada, offers compelling, cross-cultural evidence that common genetic factors underlie same-sex, sexual preference in men. In southern Mexico, individuals who are biologically male and sexually attracted to men are known as muxes. They are recognized as a third gender: Muxe nguiiu tend to be masculine in their appearance and behavior, while muxe gunaa are feminine. In Western cultures, they would be considered gay men and transgender women, respectively. Several correlates of male androphilia — biological males who are sexually attracted to men — have been shown across different cultures, which is suggestive of a common biological foundation among them. For example, the fraternal birth order effect—the phenomenon whereby male androphilia is predicted by having a higher number of biological older brothers—is evident in both Western and Samoan cultures. Interestingly, in Western society, homosexual men, compared with heterosexual men, tend to recall higher levels of separation anxiety — the distress resulting from being separated from major attachment figures, like one’s primary caregiver or close family members. Research in Samoa has similarly demonstrated that third-gender fa’afafine—individuals who are feminine in appearance, biologically male, and attracted to men—also recall greater childhood separation anxiety when compared with heterosexual Samoan men. Thus, if a similar pattern regarding separation anxiety were to be found in a third, disparate culture—in the case, the Istmo region of Oaxaca, Mexico—it would add to the evidence that male androphilia has biological underpinnings. © 2017 Scientific American

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 23540 - Posted: 04.26.2017