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

Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.

Links 1 - 20 of 2405

By Tom Garlinghouse Male and female bees may look similar, but they have dramatically different dining habits, according to a new study. Despite both needing nectar to survive, they get this nutrient from different flowers—so different, in fact, that males and females might as well belong to separate species. To make the find, researchers spent 11 weeks observing the foraging habits of 152 species of bees in several flower-rich New Jersey fields. Then they brought the insects—nearly 19,000 in all—back to the lab and meticulously identified their species and sex. Males and females rarely drank nectar from the same type of flower, the team will report in Animal Behaviour. Using a statistical test the researchers found that male and female bee diets overlap significantly less than would be expected at random. © 2018 American Association for the Advancement of Science

Keyword: Sexual Behavior
Link ID: 25776 - Posted: 12.12.2018

By Elizabeth Pennisi Anyone who has tried to whisper sweet nothings into their lover’s ear while standing on a noisy street corner can understand the plight of the túngara frog. A tiny amphibian about the size of a U.S. quarter, the male Physalaemus pustulosus has had to make its call more complex to woo mates when they move from the forest to the city. Now, researchers have found that female túngara frogs from both the country and the city prefer these mouthy city slickers. Biologists have long studied túngara frog courtship, demonstrating that visual signals and calls by themselves are unattractive to females but together are a winning combination, and that a female’s decision to mate depends on the context. Now, researchers have recorded the calls of male frogs living in cities, small towns, and forests across Panama. As they played the calls back, they counted the females, frog-eating bats, and frog-biting insects lured in by each call. Then they transplanted forest-dwelling frogs to the city and city dwellers to the forest to see how females there reacted to their calls. Finally, in the lab, they tested female preference for each call. Males living in cities and towns called more frequently and had more complex calls—with louder “chucks” interspersed in the whine—than forest frogs, the team reports today in Nature Ecology & Evolution. When they were moved into the country, they simplified their calls; but when their country cousins were brought to the big city, they couldn’t make the switch, and kept singing simply. When the researchers played back the calls to females, the females preferred more complex calls, even if the female herself was from the country, they reported. © 2018 American Association for the Advancement of Science

Keyword: Animal Communication; Sexual Behavior
Link ID: 25769 - Posted: 12.11.2018

Laura Sanders The uterus is best known for its baby-growing job. But the female organ may also have an unexpected role in memory, a study in rats suggests. The results, published online December 6 in Endocrinology, counter the idea that the nonpregnant uterus is an extraneous organ. That may have implications for the estimated 20 million women in the United States who have had hysterectomies. In the study, female rats either underwent removal of the uterus, ovaries, both organs or neither. Six weeks after surgery, researchers led by behavioral neuroscientist Heather Bimonte-Nelson of Arizona State University in Tempe began testing the rats on water mazes with platforms that were hidden just below the surface. Compared with the other groups, rats that lacked only a uterus were worse at remembering where to find the platforms as the tests turned progressively harder. The results suggest that signals that go from the uterus to the brain are somehow involved in remembering multiple bits of information at the same time. Rats lacking just a uterus had differences in their hormone levels, too, even though these rats kept their hormone-producing ovaries. Researchers have known for decades that hormones released by the ovaries can influence the brain. But finding that the uterus on its own can influence memory is a surprise, says neuroendocrinologist Victoria Luine of Hunter College of the City University of New York. Because many women have their uteruses removed but keep their ovaries, “this revelation brings up some interesting questions to explore.” |© Society for Science & the Public 2000 - 2018

Keyword: Learning & Memory; Hormones & Behavior
Link ID: 25757 - Posted: 12.07.2018

By Daphna Joel and Cordelia Fine In 17th and 18th century Europe, the rise of egalitarian ideals created the need for a scientific account of women’s inferior status. Thus was born gender biological complementarity — the notion that, as historian of science Londa Schiebinger explains in The Mind Has No Sex, “Women were not to be viewed merely as inferior to men but as fundamentally different from, and thus incomparable to, men.” It has been with us in one way or another, roping in science to explain the gender status quo, ever since. At its core is the persistent belief that men’s and women’s natures can be usefully and meaningfully carved into two categories or “natural kinds,” that are distinct, timeless, and deeply biologically grounded. Today’s version of this idea continues a centuries long quest to find the source of this hypothesized divergence in abilities, preferences, and behavior in the brain: You can find this notion at work, for instance, in popular books like John Gray’s “Men Are from Mars, Women Are from Venus” in the 1990s, Louann Brizendine’s “The Female Brain” and “The Male Brain” the following decade, and last year’s “Results at the Top: Using Gender Intelligence to Create Breakthrough Growth” by Barbara Annis and Richard Nesbitt. But a version of the same assumption is also sometimes subtly present in scientific research. Consider, for example, Cambridge University psychologist Simon Baron-Cohen’s influential Empathizing-Systemizing theory of brains and the accompanying “extreme male brain” theory of autism. This presupposes there is a particular “systemizing” brain type that we could meaningfully describe as “the male brain,” that drives ways of thinking, feeling, and behaving that distinguish the typical boy and man from the typical “empathizing” girl and woman. © 2018 The New York Times Company

Keyword: Sexual Behavior
Link ID: 25747 - Posted: 12.04.2018

Susan Milius Mom nurses her young for weeks on milk that has four times the protein of a cow’s. Yet this mother’s not a mammal. She’s a jumping spider with eight legs and a taste for fruit flies. We mammals have named ourselves after our mammary glands. Yet other animals, from tsetse flies to pigeons, secrete their own versions of milk for their babies. The newly discovered nursing in Toxeus magnus could be the most mammal-like of all, a research team from China proposes in the Nov. 30 Science. Biologists have recognized T. magnus as a species since 1933, but a small spider’s mothering habit was easy to miss. The spiders hunt beasts such as fruit flies and will retreat to a little nest, perhaps attached to a leaf, to raise a family. Study coauthor Zhanqi Chen of the Chinese Academy of Sciences in Menglunzhen, who studies spider behavior, noticed several T. magnus sharing a nest in 2012 and wondered if the species had some sort of extended parental care. It was another five years before he spotted the nursing behavior, when a spiderling clamped itself against mom’s underside one exciting July night in 2017. With a T. magnus female under a microscope, a gentle finger push on the underside of the abdomen will squeeze a tiny bead of white liquid out of a crease called an epigastric furrow, the researchers say. For the first week or so after eggs hatch, a spider mom leaves milk droplets around the nest for the crawling dots of her young to drink. Then nursing turns more mammalian, with little ones pressing themselves against their mother’s body. |© Society for Science & the Public 2000 - 2018

Keyword: Sexual Behavior; Evolution
Link ID: 25737 - Posted: 11.30.2018

By Frankie Schembri Fruit flies might not sing songs, make art, or don traditional garments, but that doesn’t mean they don’t have culture. New evidence suggests female fruit flies (Drosophila melanogaster) can create unique dating customs based on the partners they see other female fruit flies select. Cultural traditions—the traits and behaviors that are handed down across generations and spread through social learning—have been found in the grooming patterns of certain apes and the songs of some whales and birds. But scientists had little proof that smaller creatures such as insects could have culture. So researchers set up a series of experiments in which one “observer” female fruit fly watched a “demonstrator” fly pick between two males that differed only in their color—pink or green. When it was their turn to mate, observers chose the same color of mate more than 80% of the time, compared with random chance, researchers report today in Science. The team also tested how reliably preferences were passed to the next generation by placing 12 observers in the center of a hexagonal container surrounded by six demonstrators who went exclusively for either pink or green males. In the next round of mating, the first observers to mate became the demonstrators. Over the course of 36 trials, the pink or green preference “trickled down” to the eighth generation of flies before they started to choose randomly again. © 2018 American Association for the Advancement of Science

Keyword: Sexual Behavior
Link ID: 25733 - Posted: 11.30.2018

By Michael Allen When a peacock catches the attention of a female, he doesn’t just turn her head—he makes it vibrate. That’s the surprising conclusion of a new study, which finds that a male peafowl’s tail feathers create low-frequency sounds that cause feathers on the females’ heads to quiver. The finding is “fascinating,” says Richard Prum, an evolutionary ornithologist at Yale University who was not involved with the work. As far as he knows, it’s the first demonstration that feathers respond to acoustic communication signals from other birds. Scientists have long known that a bird’s feathers can sense vibrations. Much like a rodent’s whiskers, they are coupled to vibration-sensitive nerve cells, allowing them to sense their surroundings. Feathers can, for example, detect changes in airflow during flight, and some seabirds even use feathers on their heads to feel their way through dark, underground crevices. When peacocks are ready to mate, they fan out their iridescent tail feathers (known as trains), before rushing at females, shaking those feathers to catch their attention. But when researchers discovered low-frequency sounds—which are inaudible to humans—coming from this “train rattle” several years back, no one knew how they worked. All they knew was that peahens perked up and paid attention to recordings of these “infrasounds,” even though they couldn’t see the males. © 2018 American Association for the Advancement of Science

Keyword: Sexual Behavior; Animal Communication
Link ID: 25730 - Posted: 11.29.2018

By Neil Genzlinger Dorothy L. Cheney, whose careful research into how primates live and communicate revealed the surprising complexity of their thought processes and social structures, died on Friday at her home in Devon, Pa. She was 68. Her husband and research partner, Robert M. Seyfarth, said the cause was breast cancer. “Cheney was a spectacular scientist,” Robert M. Sapolsky, a professor of biology and neurology at Stanford University and the author of books like “A Primate’s Memoir,” said by email. “Along with Robert Seyfarth, she did wonderfully clever, elegant field experiments that revealed how other primates think about the world — showing that they think in far more sophisticated and interesting ways than people anticipated.” Rather than doing their research in laboratories, Dr. Cheney and Dr. Seyfarth spent long stretches in the wilds of Africa and elsewhere, studying gorillas, baboons, vervet monkeys and other animals. One of their best-known experiments, conducted in Kenya in 1977, showed that vervets made distress sounds not just involuntarily, out of fear, but to convey a specific message about a given threat. They hid loudspeakers in bushes, played recorded sounds of vervets and watched the reaction. A particular bark sent the animals scurrying up trees because it was a warning about leopards; a low-pitched staccato noise had them looking skyward for predatory eagles. They summarized their research in their first book, “How Monkeys See the World: Inside the Mind of Another Species” (1990). Later research in Botswana included insights into the hierarchical nature of baboon societies and its possible evolutionary effects. “Because Western scientists learned about primates by examining corpses or observing single animals brought home as pets,” they wrote in their 2007 book, “Baboon Metaphysics: The Evolution of a Social Mind,” “few if any ever learned what can be discovered only through long, patient observation: that the most human features of monkeys and apes lie not in their physical appearance but in their social relationships.” © 2018 The New York Times Company

Keyword: Evolution; Sexual Behavior
Link ID: 25683 - Posted: 11.15.2018

/ By Elizabeth Svoboda In 1997, a Stanford University neuroscientist wrote a letter to his colleagues. He signed the letter with his birth name, Barbara Barres, but made it clear that from now on he wished to be known as Ben. “Whenever I think about changing my gender role, I am flooded with feelings of relief,” he wrote. “Whenever I think about changing my gender role, I am flooded with feelings of relief.” “I hope that despite my trans sexuality you will allow me to continue with the work that, as you all know, I love,” he concluded his letter. To Barres’ great joy, his fellow scientists responded with unwavering support. What they didn’t know was that he’d been unable to sleep for a week as he mulled whether to transition to male or commit suicide. His new autobiography — published, sadly, after his death last year from pancreatic cancer — testifies to his personal courage on two fronts: first, as a dogged investigator of glia, the brain’s most numerous cells, which many had written off as purposeless; and second, as an advocate for female and gender-nonconforming scientists. An intense and sagacious child, Ben Barres — born Barbara — decided he wanted to be a scientist before reaching his fifth birthday. He favored microscopes and chemistry sets over dresses and jewelry. By college, it was clear his genius was equal to his dedication. He earned prestigious scholarships that helped fund a biology degree at MIT, then went on to tackle a medical degree at Dartmouth. The early challenges Barres faced often stemmed from appearing female in a male-dominated field. When he was the only person in an MIT class to solve an artificial intelligence problem, the professor scoffed and insisted his boyfriend must have done the work. Copyright 2018 Undark

Keyword: Sexual Behavior; Glia
Link ID: 25675 - Posted: 11.13.2018

Chand and several other athletes throughout sports history have failed to qualify to compete in a women's event as a result of their biology. Starting in the 1960s, sex verification tests were done to ensure that only athletes determined to be biologically female could compete as women. That's because in most sports, the top male athletes outcompete the top female athletes by about 10%. More recently the motivation behind testing has shifted to determining whether an athlete has an "unfair" advantage. Since men typically have more testosterone than women and testosterone is linked to athletic performance, current tests measure female athletes' testosterone levels to ensure they are within a certain range. Can a test determine an individual's biological sex? And can testosterone produced by an athlete's own body provide an unfair advantage? pictogram of sprinters Click on "Human Development" to learn about the development of sex organs and characteristics, including hormone levels. Click on "Case Studies" to explore the sex verification tests that have been used throughout sports history by applying them to two fictitious athletes.

Keyword: Sexual Behavior
Link ID: 25674 - Posted: 11.13.2018

Researchers funded by the National Institutes of Health have reached a milestone in their quest to catalog the brain’s “parts list.” The NIH BRAIN Initiative Cell Census Network (BICCN) has issued its first data release. Posted on a public web portal (link is external) for researchers, it profiles molecular identities of more than 1.3 million mouse brain cells and anatomical data from 300 mouse brains – among the largest such characterizations to date. BICCN research teams (link is external) focused initially on a key area of the mouse motor cortex, an area of the brain that controls movement, as a first major step in the 5-year effort. Initiated in 2017, the BICCN projects aim to build comprehensive, three-dimensional common reference brain atlases that will ultimately integrate molecular, anatomical and functional data on cell types in mouse, human and non-human primate brains. To expedite scientific impact, they are making their data immediately available to the research community via the web portal. “No single research group could do this by themselves—they needed to leverage the power of a team,” explained Joshua Gordon, M.D., Ph.D., director of the National Institute of Mental Health (NIMH), which is helping to coordinate the BRAIN Initiative effort. “The BICCN is a product of nine different teams each bringing to bear their finely-honed tools to the same brain region at the same time. By doing so, they could compare results and create a unified resource for the community.” The new molecular fingerprints cover comprehensive information on gene transcription and epigenomic signature maps of the brain cells. Each type of cell is classified according to its molecular characteristics and identifiable by telltale marker genes.

Keyword: Sexual Behavior; Epigenetics
Link ID: 25638 - Posted: 11.02.2018

by Lena Simon Four limbs. Warm blood. A love for cheese. And a hatred for infidelity. Although this may sound characteristic of the average Wisconsinite, the previous is actually also true for the California mouse. A recent University of Wisconsin news release revealed research that shows California pair-bonded mice become increasingly vocal after infidelity experiences. Experiments were designed to test how communication changes after mice have been given the opportunity to be “unfaithful” to their bonded mate. The California deer mouse, or Peromyscus californicus, is part of only 3 to 5 percent of mammal species that practice any kind of monogamy, per research from the National Science Foundation. At UW, research on the California mouse is ongoing. Josh Pultorak, a biology instructor at Madison Area Technical College and UW’s Wisconsin Institute for Discovery, led this research. He and his collaborators identified several types of sounds that the California mouse makes, all of which are ultrasonic — unable to be heard by the human ear unless slowed down to about 5 percent of their original speed. These include chirps — or “sweeps,” which are usually more peaceful sounds — and barks, which indicate aggression. Microbes in your gut could hold cure to diabetesThere are millions of microbes living in your gut. They help you digest and access nutrients your own organs would Read… The Badger Herald, 1995 - 2018

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 25637 - Posted: 11.02.2018

By Daniel Engber Two decades ago, in late summer 1998, the journal Nature came out with an outrageous claim: Both women and men, a research paper argued, prefer faces with more “girlish” features. The authors of the study, based in Scotland and Japan, had expected the opposite result—that square-jawed, hunky faces, more Harrison Ford than Leonardo DiCaprio, would be deemed more attractive. “Our team has been working on this study for four years,” one of the scientists, Ian Penton-Voak, told the New York Times in advance of publication. “When it was found early on that there was a preference for feminized male faces, nobody believed it, so we did it again, and again. The preference for a feminized face keeps coming up.” Could it really be the case that everyone prefers a man with a gentle nose and a low-T brow? If so, then why are (or were) Harrison Ford and Leonardo DiCaprio both considered highly sexy? And what about the other sexy ’90s dyads of George Clooney and Jude Law, and Johnny Depp and Nick Nolte? The Nature data were no less perplexing for evolutionary psychologists like Penton-Voak. From that field’s perspective, manly features are indicative of a male’s reproductive fitness. Given this assumption, one might guess that women have evolved to find those traits the most appealing, since they help identify the sort of men with whom you could make the strongest, most immunocompetent children. What would women get from delicate men? A year later, in the summer of ’99, Penton-Voak and colleagues offered the beginnings of an explanation. For a second study, also out in Nature, and also drawn from research done in Scotland and Japan, they once again asked young women to evaluate male faces that had been digitally feminized to varying degrees—only now they had the women do so twice, at different points during their menstrual cycles. They found that a woman’s predilection for men with girlish features waxed and waned throughout the lunar month: When she looked at faces in the days leading up to ovulation, her tastes would tend a bit more masculine; later on she’d flip back the other way. © 2018 The Slate Group LLC

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 25619 - Posted: 10.26.2018

By Kristina R. Olson On arrival at a friend's house for dinner one night in the fall of 2008, I joined the evening's youngest guest, five-year-old Noah, who was playing on the couch. Little did I know he would single-handedly change the course of my career. As a professor of developmental psychology, hanging out at the kids' table is not unusual for me. I study how children think about themselves and the people around them, and some of my keenest insights have come from conversations like this one. After some small talk, I saw Noah glance around the room, appear to notice that no one was looking and retrieve something from inside his pocket. The reveal was slow but the result unmistakable: a beloved set of Polly Pocket dolls. Over the next few years I got to know Noah well and learned more about his past (all names of children here are pseudonyms to protect their privacy). Noah's parents had first noticed that he was different from his brother in the preschool years. He preferred female playmates and toys more commonly associated with girls, but his parents were unfazed. As he got older, Noah grew out his previously short hair and replaced his fairly gender-neutral wardrobe with one that prominently featured Twinkle Toes—shoes that lit up in pink as he stepped. Unlike many similar kids, Noah's family, friends and school fully accepted him. They even encouraged him to meet other kids like himself, boys who flouted gender norms. Along with the other adults in Noah's life, I couldn't help but wonder: What did Noah's behavior mean? Was he gay? Could he just be a kid who paid less attention to gender norms than most? At the time I had no idea that these questions would soon guide my scientific research. © 2018 Scientific American

Keyword: Sexual Behavior
Link ID: 25606 - Posted: 10.23.2018

Claire Ainsworth As a clinical geneticist, Paul James is accustomed to discussing some of the most delicate issues with his patients. But in early 2010, he found himself having a particularly awkward conversation about sex. A 46-year-old pregnant woman had visited his clinic at the Royal Melbourne Hospital in Australia to hear the results of an amniocentesis test to screen her baby's chromosomes for abnormalities. The baby was fine — but follow-up tests had revealed something astonishing about the mother. Her body was built of cells from two individuals, probably from twin embryos that had merged in her own mother's womb. And there was more. One set of cells carried two X chromosomes, the complement that typically makes a person female; the other had an X and a Y. Halfway through her fifth decade and pregnant with her third child, the woman learned for the first time that a large part of her body was chromosomally male1. “That's kind of science-fiction material for someone who just came in for an amniocentesis,” says James. Sex can be much more complicated than it at first seems. According to the simple scenario, the presence or absence of a Y chromosome is what counts: with it, you are male, and without it, you are female. But doctors have long known that some people straddle the boundary — their sex chromosomes say one thing, but their gonads (ovaries or testes) or sexual anatomy say another. Parents of children with these kinds of conditions — known as intersex conditions, or differences or disorders of sex development (DSDs) — often face difficult decisions about whether to bring up their child as a boy or a girl. Some researchers now say that as many as 1 person in 100 has some form of DSD2. © 2018 Macmillan Publishers Limited

Keyword: Sexual Behavior
Link ID: 25605 - Posted: 10.23.2018

By Amanda Montañez Humans are socially conditioned to view sex and gender as binary attributes. From the moment we are born—or even before—we are definitively labeled “boy” or “girl.” Yet science points to a much more ambiguous reality. Determination of biological sex is staggeringly complex, involving not only anatomy but an intricate choreography of genetic and chemical factors that unfolds over time. Intersex individuals—those for whom sexual development follows an atypical trajectory—are characterized by a diverse range of conditions, such as 5-alpha reductase deficiency (highlighted in graphic below). A small cross section of these conditions and the pathways they follow is shown here. In an additional layer of complexity, the gender with which a person identifies does not always align with the sex they* are assigned at birth, and they may not be wholly male or female. The more we learn about sex and gender, the more these attributes appear to exist on a spectrum. *The English language has long struggled with the lack of a widely recognized nongendered third-person singular pronoun. A singular form of “they” has grown in widespread acceptance, and many people who do not identify with a binary gender use it. © 2018 Scientific American

Keyword: Sexual Behavior
Link ID: 25604 - Posted: 10.23.2018

Tina Hesman Saey SAN DIEGO — For some people, choosing a same-sex partner may be in their DNA. In a large study of more than 490,000 men and women in the United States, United Kingdom and Sweden, researchers discovered four genetic variants that occur more often in people who indicated on questionnaires that they had had same-sex sexual partners. Andrea Ganna, a geneticist at the Broad Institute of MIT and Harvard reported the results October 19 at the annual meeting of the American Society of Human Genetics. Two of the variants were specific to men’s sexual partner choice. The other two influence sex partner choice for both men and women. Collectively, the DNA differences explained only 8 to 12 percent of the heritability of having same-sex partners. “There is no gay gene,” Ganna said, “but rather non-heterosexuality is influenced by many tiny-effect genetic factors.” The new study is an advance over previous attempts to find “gay genes,” says J. Michael Bailey, a psychologist at Northwestern University in Evanston, Ill., who was not involved in the new work. The study’s size is its main advantage, Bailey says. “It’s huge. Huge.” Researchers examined DNA data from more than 400,000 participants in the U.K. Biobank and more than 69,000 people who had their DNA tested by the consumer testing company 23andMe. People who have given their DNA data to those research projects also answered a battery of questions, including ones about whether they had ever had a partner of the same sex and how many sexual partners they have had. The findings were replicated with data from three other studies, including one from Sweden. Findings from such large studies are more likely to be replicated than the small studies in the past, Bailey says. Researchers have “really gotten these studies down now and if they find things, it’s pretty sure that they’re true.” |© Society for Science & the Public 2000 - 2018

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 25601 - Posted: 10.22.2018

By Michael Price SAN DIEGO, CALIFORNIA—How genes influence sexual orientation has sparked debate for at least a quarter century. But geneticists have had only a handful of underpowered studies to address a complex, fraught, and often stigmatized area of human behavior. Now, the largest-ever study of the genetics of sexual orientation has revealed four genetic variants strongly associated with what the researchers call nonheterosexual behavior. Some geneticists are hailing the findings as a cautious but significant step in understanding the role of genes in sexuality. Others question the wisdom of asking the question in the first place. Andrea Ganna, a research fellow with the Broad Institute in Cambridge, Massachusetts, and Harvard Medical School in Boston, and colleagues examined data from hundreds of thousands of people who provided both DNA and behavioral information to two large genetic surveys, the UK Biobank study and the private genetics firm 23andMe. They analyzed DNA markers from people who answered either “yes” or “no” to the question, “Have you ever had sex with someone of the same sex?” In total, they identified 450,939 people who said their sexual relationships had been exclusively heterosexual and 26,890 people who reported at least one homosexual experience. In Ganna’s talk yesterday at the annual meeting of the American Society of Human Genetics here, he emphasized that the researchers were cautious about exploring sexual behavior that is still illegal in many countries, and that they tried to frame their questions carefully “to avoid a fishing expedition.” The team, which includes behavioral scientists, preregistered their research design and also met regularly with members of the LGBTQ community to discuss and share results. Ganna acknowledged that what they call “nonheterosexual behavior” includes “a large spectrum of sexual experiences, that go from people who engage exclusively in same-sex behavior to those who might have experimented once or twice.” © 2018 American Association for the Advancement of Science

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 25600 - Posted: 10.22.2018

Women whose left index and ring fingers are different lengths are more likely to be lesbians, a study suggests. Scientists measured the fingers of 18 pairs of female identical twins, where one was straight and the other gay. On average, the lesbians, but not the straight twins, had different sized index and ring fingers, typically a male trait, but only on the left hand. This may be the result of exposure to more testosterone in the womb, the University of Essex researchers said. The scientists also measured the fingers of 14 pairs of male identical twins, where one was straight and the other gay, but found no link. Both men and women were exposed to the "male" hormone, testosterone, in the womb - but some may be exposed more than others, the scientists said. Study author Dr Tuesday Watts, from the psychology department at Essex University, said: "Because identical twins, who share 100% of their genes, can differ in their sexual orientations, factors other than genetics must account for the differences. "Research suggests that our sexuality is determined in the womb and is dependent on the amount of male hormone we are exposed to or the way our individual bodies react to that hormone, with those exposed to higher levels of testosterone being more likely to be bisexual or homosexual. © 2018 BBC

Keyword: Sexual Behavior
Link ID: 25591 - Posted: 10.18.2018

Gina Mantica Have you ever seen a picture of a mother dog caring for an unusual baby, like a kitten? This sort of animal adoption story is an example of a phenomenon known as alloparenting: care provided to offspring that are not genetically related. We humans may toss around the phrase “It takes a village to raise a child,” but there are cases in the animal world where this is more literally true. Naked mole-rats, wrinkly mammals of the East African desert, offer an example of the whole “village” cooperating to raise offspring. Each individual naked mole-rat has a specific job. Like in a honeybee hive, a naked mole-rat colony has one queen, whose job it is to reproduce. There are just a few sexually reproductive males, who mate with the queen. All the others, both male and female, are either soldiers that protect the colony or workers that forage for food, dig tunnels and care for the queen’s offspring, known as pups. Until now, no one had a physiological explanation for why naked mole-rat workers care for pups that aren’t their own. Normally when a mom gives birth, estrogen levels are high and progesterone levels drop, resulting in maternal behaviors such as feeding or grooming. In many unusual adoption stories, like that of the mother dog caring for a kitten, the adoptive mom will have recently given birth to her own offspring – meaning her hormone levels have left her primed and ready to care for offspring, even those that aren’t her own. © 2010–2018, The Conversation US, Inc.

Keyword: Sexual Behavior; Chemical Senses (Smell & Taste)
Link ID: 25577 - Posted: 10.16.2018