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By Jackie Rocheleau Every day about 60,000 people have surgery under general anesthesia in the United States. Often casually compared to falling into a deep sleep, going under is in fact wildly different from your everyday nocturnal slumber. Not only does a person lose the ability to feel pain, form memories, or move—they can’t simply be nudged back into conscious awareness. But occasionally, people do wake unexpectedly—in about 1 out of every 1,000 to 2,000 surgeries, patients emerge from the fog of anesthesia into the harsh light of the operating room while still under the knife. One question that has dogged researchers over the past several decades is whether women are more likely to find themselves in these unfortunate circumstances. A number of recent studies, including a 2023 meta-analysis, suggest that the answer is yes. But the findings are controversial: Other studies have found no differences in waking frequency between the sexes and most of the studies were not designed specifically to identify sex differences. It’s also difficult to know whether other factors might have influenced the results: rates of metabolization of drugs by male and female bodies, as well as variation in kinds of surgeries and anesthetic regimens among study participants. No causal link had been established. Now, a new study published in the Proceedings of the National Academy of Sciences helps untangle some of the mystery. In a series of experiments in mice and in humans, the researchers found that females do wake more easily from anesthesia and that testosterone plays an important role in how quickly and deeply we go under, and how easily we wake up. “There seems to be something hardwired into the female brain that biases it more toward a state of wakefulness,” says University of Pennsylvania anesthesiologist Max Kelz, co-author of the study. © 2024 NautilusNext Inc., All rights reserved.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 10: Biological Rhythms and Sleep
Link ID: 29156 - Posted: 02.22.2024

By Christine Dell'Amore Thunderclouds rolled across Kenya’s Masai Mara savanna as the spotted hyena cubs played, tumbling over each other in the wet grass. The cubs’ mother lounged nearby, rising occasionally to discourage a bigger one-year-old from joining the little play group. When the older animal approached again, one of the pluckier cubs took a cue from its high-ranking mom and stood tall, trying its best to look intimidating. That action seemed comical, but both animals knew their place. The larger, lower ranking hyena stopped short, then bowed its head and slunk off. Photographer Jen Guyton recorded this scene with an infrared camera, allowing an intimate look into hyenas’ nocturnal behaviors. In doing so, she provided a small window into the intriguing structure of hyena society, where all members inherit their place in the pecking order from their mother. Females are in charge, and rank means everything—a matrilineal system that has fueled the spotted hyena’s rise as the most abundant large carnivore in Africa. These and other insights into hyena behavior wouldn’t be possible were it not for 35 years of on-the-ground research by Kay Holekamp, founder of the Mara Hyena Project. Her efforts have helped reveal a creature noted for its advanced society, cognition, and ability to adjust to new surroundings. Holekamp, a biologist at Michigan State University, has been studying the African species in the Masai Mara since 1988—one of the longest running investigations of any mammal ever. “I thought I’d be there for two years,” she says, “but I got hooked.” Hooked on hyenas? Mention their name, and most people grimace. Aristotle described them as “exceedingly fond of putrefied flesh.” Theodore Roosevelt called them a “singular mixture of abject cowardice and the utmost ferocity.” Across Africa, hyenas are seen as evil, greedy, and associated with witchcraft and sexual deviance. Even the 1994 movie The Lion King portrayed them as cunning and malicious. © 1996-2015 National Geographic Society

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 29149 - Posted: 02.13.2024

Nicola Davis Science correspondent Breaking up is hard to do, but it seems the brain may have a mechanism to help get over an ex. Researchers studying prairie voles say the rodents, which form monogamous relationships, experience a burst of the pleasure hormone dopamine in their brain when seeking and reuniting with their partner. However, after being separated for a lengthy period, they no longer experience such a surge. “We tend to think of it as ‘getting over a breakup’ because these voles can actually form a new bond after this change in dopamine dynamics – something they can’t do while the bond is still intact,” said Dr Zoe Donaldson, a behavioural neuroscientist at CU Boulder and senior author of the work. Writing in the journal Current Biology, the team describe how they carried out a series of experiments in which voles had to press levers to access either their mate or an unknown vole located on the other side of a see-through door. The team found the voles had a greater release of dopamine in their brain when pressing levers and opening doors to meet their mate than when meeting the novel vole. They also huddled more with their mate on meeting, and experienced a greater rise in dopamine while doing so. Donaldson said: “We think the difference is tied to knowing you are about to reunite with a partner and reflects that it is more rewarding to reunite with a partner than go hang out with a vole they don’t know.” However, these differences in dopamine levels were no longer present after they separated pairs of voles for four weeks – a considerable period in the lifetime of the rodents. Differences in huddling behaviour also decreased. The researchers say the findings suggest a devaluation of the bond between pairs of voles, rather than that they have forgotten each other. © 2024 Guardian News & Media Limited

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 29104 - Posted: 01.18.2024

By Carissa Wong Researchers have identified some of the earliest known cases of sex-chromosome syndromes — in five ancient humans. “It’s quite interesting to think that these people existed throughout human history and how they seem to have been part of their societies,” says Kyriaki Anastasiadou, who studies ancient genomics at the Francis Crick Institute in London and is a co-author of the study, which was published on 11 January in Communications Biology1. People with extra or missing chromosomes often have differences in appearance and behaviour compared with others in the population. By identifying individuals who had these genetic syndromes, the researchers could illuminate how past societies viewed and treated people with differences. Through sequencing ancient DNA, researchers have previously found2 ancient people with an atypical number of chromosomes, including an infant with Down syndrome — caused by an extra copy of chromosome 21 — who lived around 5,000 years ago. Anastasiadou and her colleagues have now discovered the first prehistoric person known to have had Turner syndrome, which occurs in females and is characterized by having only one complete copy of the X chromosome, instead of the two copies usually found in females (males have one X and one Y). The person lived in Somerset, UK, roughly 2,500 years ago, during the Iron Age. People with Turner syndrome tend to be shorter than average and experience fertility problems. The other people the researchers identified with sex-chromosome syndromes were male. Among them was the earliest known person to have an extra Y chromosome, known as Jacob’s syndrome, which is linked to being taller than average. The man lived around 1,100 years ago, during the Early Medieval Period. The team also found three ancient males from different points in time who had an extra X chromosome, a condition known as Klinefelter syndrome, which is linked to growing taller than average and having broader hips and larger breasts. © 2024 Springer Nature Limited

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 29099 - Posted: 01.16.2024

Diana Fleischman Because of the flaming culture wars, feminists and others who disagree about the nature of sex or sex differences often ascribe significant harms to researchers who claim that sex is binary or who acknowledge biological sex differences. These perceived harms include oppression, inequality, and even murder and suicide. As a result, many influential voices in the sex difference debate rarely engage in dialogue. This context made “The Big Conversation”—an October conference that brought together a diverse group of feminists, evolutionary psychologists, biologists, and neuroscientists—such a remarkable event. The rarity of such a meeting was highlighted by the cancellation of a panel on sex differences at an annual anthropological conference just a few days before. People who had sniped at each other for years through academic papers and social media not only shared stages and panels, they broke bread together. Attendees on all sides of the issue held my baby, whom I brought along. The fear of meeting ideological opponents often leads to the expectation of hostility in person, but what’s worse is that you often will come to like them! The Big Conversation took years to come together. It was organized by sex difference expert Marco Del Giudice and Paul Golding of the Santa Fe Boys Foundation. This foundation is dedicated to exploring how to help boys and young men and was the event’s sponsor. The conference featured 16 talks and 5 discussion sections. The entire conference is available for viewing (for free!) on the Santa Fe Boys Foundation website. A central questions in sex difference research concerns the origins of differences between men and women. Are these differences primarily the result of socialization, culture, and stereotype effects, or are these differences largely innate or biological? We can call these perspectives, as Carole Hooven did during her talk, the strong socialization view and the strong biology view, respectively. Many of the conference attendees, like Gina Rippon, Cordelia Fine and Daphna Joel, endorse the strong socialization view of sex differences, arguing that men and women are innately psychologically similar but are driven into different roles by cultural forces and socialization. This perspective sparks controversy surrounding discussions on biological sex differences because its proponents argue that legitimizing and publicizing sex differences creates them where they did not exist before. © 2024 Colin Wright

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 29095 - Posted: 01.13.2024

By Rodrigo Pérez Ortega Politically and ethically fraught, research into what leads to bisexual behavior or exclusive homosexuality typically sparks controversy. The latest study, published today in Science Advances, is no exception. By mining a DNA database of some 450,000 people in the United Kingdom, a research team has concluded that the genes underlying bisexual behavior are distinct from those driving exclusive same-sex behavior, and may be intertwined with a propensity for taking risks. This connection to risk-taking, the authors suggest, may also explain why men with a history of bisexual behavior still have a reasonably high number of offspring, albeit fewer than heterosexual men, possibly explaining why the genes driving such sexual behavior have persisted. The work has drawn a mix of strong reactions. Some scientists called the findings valuable, whereas others found fault with the underlying data. Still others argued the research could potentially stigmatize sexual minorities. The result that bisexuality is tied with risky behavior, some scientists say, could be used by others to discriminate against, and further perpetuate false narratives about, bisexual people. However, study co-author Jianzhi Zhang, an evolutionary geneticist at the University of Michigan (UM), counters that the association between bisexual behavior and risk-taking “is an empirical observation. … We hold no moral judgement on risk-taking and believe [it] has pros and cons (depending on the situation), as almost any trait.” He also pushes back at the idea such research should be taboo or off limits. “We should welcome more studies of bisexuality and homosexuality. … This is partly a biological question, so we should understand it.” From one stark evolutionary perspective, sex without the prospect of producing children could be seen as waste of time and energy—behavior that might be selected against. Yet population surveys have consistently found that about 2% to 10% of people engage in sex with others of the same sex. Studies of twins have suggested such sexual activity is at least partly heritable, and therefore has a genetic component. And scientists have proposed several evolutionary theories explaining why same-sex sexual behavior may persist.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 12: Psychopathology: The Biology of Behavioral Disorders
Link ID: 29080 - Posted: 01.06.2024

Anil Oza Researchers have long known that areas of songbird brains that are responsible for singing grow during mating season and then shrink when the season is over. But one species, Gambel’s white-crowned sparrow (Zonotrichia leucophrys gambelii), does this on a scale that scientists are struggling to understand. A part of the male sparrow’s brain called the HVC grows from around 100,000 neurons to about 170,000 — nearly doubling in size — during the bird’s mating season. Although how the bird pulls off this feat is still a mystery, scientists who presented data at the annual Society for Neuroscience meeting in Washington DC on 11–15 November are closing in on answers. They hope their findings might one day point to ways of treating anomalies in the human brain. In most animals, when a brain region grows and shrinks, “frequently, it’s pretty detrimental on behaviour and function of the brain”, says Tracy Larson, a neuroscientist at the University of Virginia in Charlottesville who led the work. In particular, growth on this scale in mammals would cause inflammation and increase the pressure inside their skulls. But when it comes to the sparrows, “there’s something really fascinating about these birds that they can manage to do this and not have detrimental impacts”, Larson adds. Larson’s research has so far hinted that the sparrow’s brain is using a slew of tactics to quickly form and then kill a large number of neurons. One question that Larson wanted to answer is how the sparrow’s brain shrinks dramatically at the end of mating season. So she and her colleagues tagged cells in and around the HVCs of male sparrows with a molecule called bromodeoxyuridine (BrdU), which can become incorporated into the DNA of dividing cells. They also used hormone supplements to simulate breeding season in the birds. © 2023 Springer Nature Limited

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 19: Language and Lateralization
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 15: Language and Lateralization
Link ID: 29029 - Posted: 12.02.2023

By Annie Roth A few years ago, Nicolas Fasel, a biologist at the University of Lausanne in Switzerland, and his colleagues developed a fascination with the penises of serotine bats, a species found in woodlands and the attics of old buildings across Europe and Asia. Serotine bats sport abnormally long penises with wide, heart-shaped heads. When erect, the members are around seven times longer than the female’s vagina, and their bulbous heads are seven times wider than the female’s vaginal opening. “We wondered: How does that work? How can they use that for copulation?” Dr. Fasel recalled. What they discovered has overturned an assumption about mammalian reproduction, namely that procreation must always involve penetration. In a study, published Monday in the journal Current Biology, Dr. Fassel and his colleagues presented evidence that serotine bats mate without penetration, making them the first mammals known to do so. Instead of using their penises to penetrate their partners, the scientists found, the male bats use them to push their partner’s tail membrane out of the way so they can align their openings and engage in contact mating, a behavior similar to one found in birds and known as “cloacal kissing.” To learn how these bats overcome their substantial genital size difference, Dr. Fasel and his colleagues analyzed nearly 100 videos of serotine bats mating. The videos were provided by a bat rehabilitation center in Ukraine and a citizen scientist filming bats in the attic of a church in the Netherlands. The footage revealed a mating strategy unlike any other used by mammals. While the two bats hang upside down, the male climbs on the female’s back and grasps the nape of her neck. Once he has a firm hold, the male will use his erect penis to push the female’s tail membrane to the side and probe between her legs until he has located her vulva. The male then presses the heart-shaped head of his penis to the female’s vulva and holds it there until the deed is done. While this process took less than an hour for most of the couples the researchers observed, one pair went at it for nearly 13 hours. “It’s a really weird reproductive strategy, but bats are weird and have a lot of weird reproductive strategies,” said Patty Brennan, a biologist at Mount Holyoke College in Massachusetts who studies the evolution of genital morphology but was not involved in the study. © 2023 The New York Times Company

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 29014 - Posted: 11.22.2023

Nicola Davis Science correspondent When it comes to avoiding unwanted male attention, researchers have found some frogs take drastic action: they appear to feign death. Researchers say the findings shed new light on the European common frog, suggesting females do not simply put up with the male scramble for mates – a situation in which several males can end up clinging to a female, sometimes fatally. “It was previously thought that females were unable to choose or defend themselves against this male coercion,” said Dr Carolin Dittrich, the first author of the study from the Natural History Museum of Berlin. But the research suggests this may not be the case. “Females in these dense breeding aggregations are not passive as previously thought,” Dittrich said. Writing in the journal Royal Society Open Science, Dittrich and her co-author, Dr Mark-Oliver Rödel, report how they placed each male frog in a box with two females: one large and one small. The mating behaviour was then recorded on video. The results, obtained from 54 females who experienced the clutches of a male, revealed that 83% of females gripped by a male tried rotating their body. Release calls such as grunts and squeaks were emitted by 48% of clasped females – all of whom also rotated their body. Tonic immobility – stiffening with arms and legs outstretched in a pose reminiscent of playing dead – occurred in 33% of all females clasped by a male, with the team adding it tended to occur alongside rotating and calling. Smaller females, they note, more frequently employed all three tactics together than larger ones. While unusual, tonic immobility – it turned out – had been seen before. “I found a book written in 1758 by Rösel von Rosenhoff describing this behaviour, which was never mentioned again,” Dittrich said. © 2023 Guardian News & Media Limited

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 28956 - Posted: 10.12.2023

Hannah Devlin Science correspondent Pregnancy leads to a permanent rewiring of neurons, according to research that gives new insights into the influence of hormones on behaviour. The research, in mice, revealed that their parenting instincts were triggered by changes in the brain that occur in response to oestrogen and progesterone late in pregnancy. Similar changes are likely to occur in the human brain, according to scientists, who said the work could pave the way for fresh understanding into parenting behaviour and postpartum mental health. Dr Jonny Kohl, who led the research at London’s Francis Crick Institute, said: “We know that the female body changes during pregnancy to prepare for bringing up young. One example is the production of milk, which starts long before giving birth. Our research shows that such preparations are taking place in the brain, too.” The findings are consistent with brain imaging research in women showing changes to brain volume and brain activity that endure long after pregnancy. Although Kohl pointed out that “parenting is obviously a lot more complex in humans”. “We have NCT classes, observational learning, all these environmental influences,” he added. “We don’t have to rely on those hormonal changes to such a degree.” a newborn baby boy is checked by nurses in a hospital maternity theatre Smoking in pregnancy increases risk of premature birth threefold, study finds Read more The studies were carried out in mice, which undergo a dramatic shift in behaviour, with virgin females showing no interest in pups, and mouse mothers spending most of their time looking after young. Previously it had been widely assumed that the onset of this behaviour occurred during or just after birth, possibly triggered by hormones such as oxytocin. However, the latest research puts the change at an earlier stage and also suggests that the changes may be permanent. © 2023 Guardian News & Media Limited

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 28949 - Posted: 10.07.2023

By Carl Zimmer In more than 1,500 animal species, from crickets and sea urchins to bottlenose dolphins and bonobos, scientists have observed sexual encounters between members of the same sex. Some researchers have proposed that this behavior has existed since the dawn of the animal kingdom. But the authors of a new study of thousands of mammalian species paint a different picture, arguing that same-sex sexual behavior evolved when mammals started living in social groups. Although the behavior does not produce offspring to carry on the animals’ genes, it could offer other evolutionary advantages, such as smoothing over conflicts, the researchers proposed. “It may contribute to establishing and maintaining positive social relationships,” said José Gómez, an evolutionary biologist at the Experimental Station of Arid Zones in Almería, Spain, and an author of the new study. But Dr. Gómez cautioned that the study, published on Tuesday in the journal Nature Communications, could not shed much light on sexual orientation in humans. “The type of same-sex sexual behavior we have used in our analysis is so different from that observed in humans that our study is unable to provide an explanation for its expression today,” he said. Previous studies of same-sex sexual behavior have typically involved careful observations of a single species, or a small group of them. Dr. Gómez and his colleagues instead looked for the big evolutionary patterns that gave rise to the behavior in some species but not others. The researchers surveyed the 6,649 species of living mammals that arose from reptilelike ancestors starting roughly 250 million years ago. Looking over the scientific literature, they noted which of them had been seen carrying out same-sex sexual behaviors — defined as anything from courtships and mating to forming long-term bonds. The researchers ended up with a list of 261 species, or about 4 percent of all mammalian species, that exhibited these same-sex behaviors. Males and females were about equally likely to be observed carrying out same-sex sexual behavior, the analysis showed. In some species, only one sex did. But in still others — including cheetahs and white-tailed deer — both males and females engaged in same-sex sexual behavior. © 2023 The New York Times Company

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 28943 - Posted: 10.05.2023

By Till Hein Human couples could learn a lot from seahorses. The marine marvels spend only quality time together. They flirt, swim together, and mate. The rest of time they go their own way, drifting in ocean currents, leisurely eating their fill. But they do look forward to getting together again. Right after sunrise, male and female seahorses approach one another, gently rubbing their noses together and then begin to circle each other. Many of them make seductive clicking noises. The partners gracefully rock back and forth, as though to the beat of underwater music. They dance and cuddle together dreamily, as though they’ve lost track of time. However, love can be dangerous for seahorses. During partner dancing, hormones are released that can make their camouflage fade. This causes changes in color, so their bodies begin to glow, and the contrasts in the patterns of their skin become more pronounced. Researchers hypothesize this is how seahorses signal their willingness to mate. The partner dances also serve as a means of seduction. Before mating, courtship can take many hours. Finally, the female signals that she’s ready. She swims up toward the water surface, pointing her snout toward the sky, and stretches her body out straight as a stick—a pose that is irresistible to the male. The stallion of the sea presses his chin against his chest and makes his prehensile tail open and close like a switchblade. This enables him to pump water into his brood pouch to show his beloved mare of the sea how roomy it is. Soon afterward, the mare and stallion of the sea snuggle up together closely and let themselves drift upward. They press their bodies together so that their snouts and abdomens are touching. On account of the curves in their body posture, the space between them looks like the shape of a heart. Then, something amazing takes place. A tubular rod appears in the middle of the female seahorse’s belly, which looks a little like a penis, the so-called ovipositor. At the climax of the love scene, both partners lift their heads as though in ecstasy, curving their backs, and the female seahorse transfers her eggs into the male’s brood pouch, while her partner fertilizes them with his sperm. © 2023 NautilusNext Inc., All rights reserved.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 28923 - Posted: 09.23.2023

Hannah Devlin Science correspondent The brain circuit that causes the sound of a newborn crying to trigger the release of breast milk in mothers has been uncovered by scientists. The study, in mice, gives fresh insights into sophisticated changes that occur in the brain during pregnancy and parenthood. It found that 30 seconds of continuous crying by mouse pups triggered the release of oxytocin, the brain chemical that controls the breast-milk release response in mothers. “Our findings uncover how a crying infant primes its mother’s brain to ready her body for nursing,” said Habon Issa, a graduate student at NYU Langone Health and co-author of the study. “Without such preparation, there can be a delay of several minutes between suckling and milk flow, potentially leading to a frustrated baby and stressed parent.” The study showed that once prompted, the surge of hormones continued for roughly five minutes before tapering off, enabling mouse mothers to feed their young until they were sated or began crying again. The observation that a mother’s breasts can leak milk when they hear a crying baby is not new. But the latest research is the first to identify the brain mechanisms behind what the scientists described as the “wail-to-milk pipeline”, and could pave the way for a better understanding of the challenges of breastfeeding for many women. The findings, published in Nature, showed that when a mouse pup starts crying, sound information travels to an area of its mother’s brain called the posterior intralaminar nucleus of the thalamus (PIL). This sensory hub then sends signals to oxytocin-releasing brain cells (neurons) in another region called the hypothalamus. Most of the time these hypothalamus neurons are “locked down” to prevent false alarms and wasted milk. However, after 30 seconds of continuous crying, signals from the PIL built up and overpowered the in-built inhibitory mechanism, setting off oxytocin release. © 2023 Guardian News & Media Limited

Related chapters from BN: Chapter 5: Hormones and the Brain; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 28919 - Posted: 09.21.2023

By Sarah Lyall The author Cat Bohannon was a preteen in Atlanta in the 1980s when she saw the film “2001: A Space Odyssey” for the first time. As she took in its famous opening scene, in which a bunch of apes picks up a bunch of bones and quickly begins using them to hit each other, Bohannon was struck by the sheer maleness of the moment. “I thought, ‘Where are the females in this story?’” Bohannon said recently, imagining what those absent females might have been up to at that particular time. “It’s like, ‘Oh, sorry, I see you’re doing something really important with a rock. I’m just going to go over there behind that hill and quietly build the future of the species in my womb.” That realization was just one of what Bohannon, 44, calls “a constellation of moments” that led her to write her new book, “Eve: How the Female Body Drove 200 Million Years of Human Evolution.” A page-turning whistle-stop tour of mammalian development that begins in the Jurassic Era, “Eve” recasts the traditional story of evolutionary biology by placing women at its center. The idea is that by examining how women evolved differently from men, Bohannon argues, we can “provide the latest answers to women’s most basic questions about their bodies.” These include, she says: Why do women menstruate? Why do they live longer? And what is the point of menopause? These are timely questions. Thanks to regulations established in the 1970s, clinical trials in the United States have typically used mostly male subjects, from mice to humans. (This is known as “the male norm.”) Though that changed somewhat in 1994, when the National Institutes of Health updated its rules, even the new protocols are replete with loopholes. For example: “From 1996 to 2006, more than 79 percent of animal studies published in the scientific journal Pain included only male subjects,” she writes. © 2023 The New York Times Company

Related chapters from BN: Chapter 6: Evolution of the Brain and Behavior; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 28907 - Posted: 09.13.2023

Nicola Davis Science correspondent Whether it’s seeing Jesus in burnt toast, a goofy grin in the grooves of a cheese grater, or simply the man in the moon, humans have long perceived faces in unlikely places. Now researchers say the tendency may not be fixed in adults, suggesting it appears to be enhanced in women who have just given birth. The scientists suggest the finding could be down to postpartum women having higher levels of oxytocin, colloquially referred to as the “love” or “trust” hormone because of its role in social bonding. “These data, collected online, suggest that our sensitivity to face-like patterns is not fixed and may change throughout adulthood,” the team write. Writing in the journal Biology Letters, researchers from Australia’s University of Queensland and the University of the Sunshine Coast describe how they set out to investigate whether the propensity to see faces in inanimate objects – a phenomenon known as face pareidolia – changes during life. Previous research has suggested that when humans are given oxytocin, their ability to recognise certain emotions in faces increases. As a result, the team wanted to explore if the hormone could play a role in how sensitive individuals are towards seeing faces in inanimate objects. The researchers used an online platform to recruit women, with participants asked if they were pregnant or had just given birth – the latter being a period when oxytocin levels are generally increased. The women were each shown 320 images in a random order online and asked to rate on an 11-point scale how easily they could see a face. While 32 of the images were of human faces, 256 were of inanimate objects with patterns that could be said to resemble a face, and 32 depicted inanimate objects with no such facial patterns. The team gathered data from 84 pregnant women, 79 women who had given birth in the past year, and 216 women who did not report being pregnant or having recently had a baby. © 2023 Guardian News & Media Limited

Related chapters from BN: Chapter 5: Hormones and the Brain; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 14: Attention and Higher Cognition
Link ID: 28906 - Posted: 09.13.2023

By Veronique Greenwood Floating languorously through forests and jungles of the Americas, longwing butterflies have many secrets. The 30-odd species in this group include many mimics. The wing markings on some distantly related species of longwings are so similar they inspired one Victorian naturalist to theorize that harmless species could mimic deadly ones to avoid predators. In the age of genomic sequencing, biologists have found other oddities in longwings. In a paper published last week in the Proceedings of the National Academy of Sciences, researchers report that female zebra longwings can see colors that males cannot, thanks to a gene on their sex chromosome. Understanding how it got there might shed light on how differences between sexes can evolve. Like primates, butterflies have a handful of proteins that are sensitive to certain wavelengths of light that, working together, produce the ability to distinguish colors. Curious about the zebra longwing’s vision, Adriana Briscoe, a professor at the University of California, Irvine, and an author of the new paper, asked a student to check the species’ genome for a well-known color vision gene. The gene, known as UVRh1, codes for a protein that is sensitive to ultraviolet light. To her surprise, it was nowhere to be found. Digging deeper, and drawing on genomic data from additional zebra longwings, Dr. Briscoe and her colleagues discovered that UVRh1 was there, but only in females. With lab experiments, they confirmed that females could see markings males couldn’t. They eventually pinpointed the gene in an unexpected place: the butterfly’s tiny sex chromosome. Sex chromosomes in butterflies are unstable, often shedding genes that are picked up by other chromosomes, or lost entirely, Dr. Briscoe said. That makes them a somewhat unusual place to keep something as important as a gene for color vision. © 2023 The New York Times Company

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 28872 - Posted: 08.19.2023

By Alejandra Manjarrez Rafael Jiménez Medina learned how to hunt elusive Iberian moles in the fields of southern Spain in the 1980s, when he was a young PhD student in genetics at the University of Granada. A local hunter of the moles (Talpa occidentalis) taught him how to capture these solitary, aggressive and territorial animals. The moles dig subterranean galleries and labyrinths in the meadows of the Iberian Peninsula, especially those with soft soils rich in earthworms, their favorite food. Such activity can benefit the soil — by aerating or mixing it — but the moles’ presence and constant movement in cultivated land raise the ire of farmers, who pay hunters to get rid of them. Jiménez Medina had a different motivation for hunting these subterranean mammals. His doctoral project was to visualize and analyze their chromosomes, which meant collecting, preparing and examining samples from the testes of males. His lab analyses led to a curious finding: Some of the moles he had identified as males were in fact genetically females — that is, their sex chromosomes were XX (female) and not XY (male). The confusion, we now know, stems from the unusual composition of the reproductive organs of female moles. In contrast to most female mammals, which have only ovaries, female Iberian moles also have testicular tissue. This tissue anatomically resembles male testicles but differs in that it produces testosterone but no sperm. The female mole’s organs are composed of both an ovarian and a testicular portion and are known as ovotestes. In addition, female moles have a clitoris covered with a foreskin and with an elongated appearance that resembles a penis; they urinate through this structure. Another unique anatomical feature is that during these females’ juvenile stage, the vaginal orifice remains closed. © 2023 Annual Reviews

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 28849 - Posted: 07.19.2023

By Darren Incorvaia When Ambika Kamath was a graduate student in evolutionary biology at Harvard University, she knew one thing for sure: She wasn’t going to research anoles, the lizards that her adviser, Jonathan Losos, specialized in. “I started out as one of those rebellious renegades,” Kamath says, determined to pursue her own research subject. So she went to India for a couple of years to study the poorly understood fan-throated lizards. But when she tried to map out their territories, she found chaos. “All of the lizards were moving everywhere,” she says. Losos encouraged her to work with anoles after all, because it was well established that males hold individual territories that they protect from other males, and females only mate with the male whose territory they reside in. That would make it more straightforward for Kamath to study how anole territoriality differed across habitat types, like forests and parks. So Kamath went to Florida, where she identified individual anoles and tracked their movements day in, day out. Kamath studied the anoles “in a larger area, in a longer period of time than anyone else had ever done,” says Losos, who is now at Washington University in St. Louis. But instead of revealing territorial differences, this massive dataset showed that the anoles weren’t actually territorial in the first place. Kamath looked into the historical record to see where the idea of anole territoriality originated. It started with a 1933 paper that described frequent sexual behavior between male lizards in the lab. The authors had concluded that this lab behavior must be “prevented by something” in the wild, Kamath says, which they inferred was the males protecting territories. “The very first conclusion,” she says, “was based on a homophobic response to observing male-male copulation.” That shaky conclusion caught on, and later researchers assumed it to be true. Introducing a feminist perspective © Society for Science & the Public 2000–2023.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 28842 - Posted: 07.06.2023

By Azeen Ghorayshi For decades, male mice have been the default in scientific experiments that test new drugs or examine the connections of the brain. The reason? Female mice, which experience a four- to five-day cycle of fluctuating ovarian hormones, were thought to be too complicated. Accounting for the hormonal changes was viewed as too cumbersome and too expensive. But the estrous cycle has little to do with how female mice behave, according to a new study that used machine-learning software to track the second-to-second behavior of animals exploring an open space. Male mice actually exhibited more erratic behavior than females did. The study, published in the journal Current Biology on Tuesday, challenges century-old stereotypes that kept female animals out of laboratory research — and, until the 1990s, barred women from clinical trials. The new research is “tipping all of these assumptions about sex differences and the influence of hormones on their head,” said Rebecca Shansky, a behavioral neuroscientist at Northeastern University and a co-author of the new study. The cost of excluding females — whether human or animal — from scientific research is high. Women are almost twice as likely as men to experience severe side effects from drugs, most of which have dosages based on the initial testing done in men. Women also may not derive the same benefits from the drugs. Women “capable of becoming pregnant,” as the federal government put it, were largely excluded from clinical trials of drugs until 1993, when a new law required researchers funded by the National Institutes of Health to include women and minority groups. In the decades since, women have made up close to half of clinical research participants, though they still lag behind in studies of certain drugs, like those used to treat cardiovascular disease and psychiatric disorders. But a large sex gap persisted in basic science research using lab animals, studies that pave the way to medical breakthroughs. In neuroscience, according to a review published in 2010, studies of male lab animals outnumbered female ones by a factor of five. © 2023 The New York Times Company

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 28694 - Posted: 03.08.2023

By Elizabeth Preston A fully grown male orca is one of the planet’s fiercest hunters. He’s a wily, streamlined torpedo who can weigh as much as 11 tons. No other animal preys on him. Yet in at least one population, these apex predators struggle to survive without their moms, who catch their food and even cut it up for them. Scientists have previously seen that some killer whale mothers share food with their grown sons. In a study published Wednesday in Current Biology, researchers found that this prolonged feeding carries a huge reproductive cost for mothers. Killer whales, actually the largest members of the dolphin family, swim throughout the world’s oceans. Yet they live in discrete populations with their own territories, dialects and hunting customs. A group that spends much of the year off the coast of British Columbia, Washington and Oregon is known as the southern residents. They eat mainly Chinook salmon, which have been increasingly hard to find. “Killer whales worldwide are doing fine,” said Michael Weiss, research director at the Center for Whale Research in Friday Harbor, Wash. But the southern residents, with a population of just 73, are considered endangered. These whales stay with their birth family for their whole lives. The families are led by matriarchs who can live 80 to 90 years. Yet the females stop reproducing in midlife: Orcas and a few other whale species are the only mammals, besides humans, known to undergo menopause. To try to explain menopause, scientists have looked for ways that matriarchs encourage the survival of their children and grandchildren. A 2012 study of southern resident killer whales, along with their neighbors, the northern residents, showed that the presence of older moms helped adult offspring stay alive — especially sons. Males over age 30 were eight times more likely to die in the year following their own mothers’ deaths. © 2023 The New York Times Company

Related chapters from BN: Chapter 6: Evolution of the Brain and Behavior; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 28662 - Posted: 02.11.2023