Links for Keyword: Sexual Behavior

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By Phie Jacobs Whether it’s two newlyweds going in for a smooch after saying “I do” or a parent soothing their child’s scraped knee, kissing is one of humanity’s most recognizable symbols of affection. Clay tablets from ancient Mesopotamia dating to 2500 B.C.E. provide the earliest archaeological evidence of romantic kissing. But the behavior may be older than civilization itself, with some studies suggesting Neanderthals swapped spit with modern humans—and shared each other’s oral microbes—more than 100,000 years ago. Some researchers have suggested kissing evolved from behaviors such as sniffing, nursing babies, or even parents passing chewed-up food to their offspring. But in an article published this month in Evolutionary Anthropology, evolutionary psychologist Adriano Lameira of the University of Warwick offers another hypothesis. Drawing on his knowledge of great ape behavior, Lameira suggests kissing got its start as a fur grooming ritual still observed in modern-day chimpanzees and other great apes. Science sat down with Lameira to learn more about his work. This interview has been edited for length and clarity. Q: What made you want to study kissing? A: It’s a behavior that is charged with so much meaning and symbolism, perhaps the most iconic way of how we show affection on an individual and societal level. I was surprised to find that we know so little about its evolution and nature. In our lab, we’re mostly intrigued by the evolution of language, dance, and imagination. But in the largest sense we’re interested in behaviors and rituals that are evolutionary heirlooms from our apelike ancestors—things our ancestors did that set us on course towards who we are today. Q: Do other animals kiss, or is the behavior unique to humans? © 2024 American Association for the Advancement of Science.

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: 29532 - Posted: 10.30.2024

By Sofia Quaglia Parenting can be lots of work for a bird: all that flying back and forth transporting grubs and insects to a nest of demanding young. But some birds manage to forgo caring for their chicks — while still ensuring they’re well looked after. These birds lay their eggs in the nests of other birds that unknowingly adopt the hatchlings, nourishing and protecting them as their own. Only about 1 percent of all bird species resort to this sneaky family planning method, called obligate brood parasitism, but it has evolved at least seven separate times in the history of birds and is a way of life for at least 100 species. Since some brood parasites rely on several different bird species as foster parents, more than a sixth of all species in the avian world care for chicks that aren’t their own at some point. Throughout the millennia, these trespassers have evolved ingenious ways to fool the hosts, and the hosts have developed equally clever ways to protect themselves and their own. At each stage of the nesting cycle, it’s a game of subterfuge that plays out in color, sound and behavior. “There’s always something new — it’s like, ‘Oh, man, this group of birds went down a slightly different pathway,’” says behavioral ecologist Bruce Lyon of the University of California, Santa Cruz, who studies the black-headed duck (Heteronetta atricapilla), the sole obligate parasitic duck species. While many mysteries remain, new research is constantly unearthing just how intense this evolutionary tug-of-war can get.

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: 29505 - Posted: 10.05.2024

By Laura Sanders Pregnancy overhauls a woman’s body. The brain is no exception. A detailed study of a woman’s brain before, during and after pregnancy revealed sweeping neural changes, some of which stuck around months after her baby was born. The dataset, published September 16 in Nature Neuroscience, is the first comprehensive view of the neural changes that accompany gestation — a sort of “what to expect when you’re expecting” for the brain. “The results of this case study are astonishing,” says neuroscientist Clare McCormack of New York University Langone Health. “Here we see, for the first time in humans, the extent of brain changes that are under way throughout pregnancy.” This research joins a small number of other studies aimed at understanding the female brain at various stages of life (SN: 9/29/22). Collectively, the work suggests that the process of becoming a mother, called matrescence, is another stage of development, like the brain overhaul that happens in adolescence (SN: 2/27/23). Earlier experiments mostly compared brains of women before and after their pregnancies and inferred what happens in between (SN: 12/19/16). “There was a missing piece,” McCormack says. “The nine months of pregnancy was a black box, and we could only guess what that trajectory looks like.” With four MRI scans before pregnancy, 15 scans during pregnancy and seven scans in the two years after the baby was born, the new study follows the entire arc for one mother. © Society for Science & the Public 2000–2024.

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: 29485 - Posted: 09.18.2024

By Liam Drew In November 2008, neuroscientist Susana Carmona — then a postdoc studying attention deficit hyperactivity disorder — was driving two colleagues to a party when one of them revealed that she was thinking about having a child. The trio became so engulfed in conversation about how pregnancy might change her brain that they diverted from the party and headed to their laboratory to search the literature. They found numerous studies in rodents, but in humans, “there was basically nothing at all”, says Carmona. Shocked by this gap in research, Carmona and her colleagues convinced their mentor at the Autonomous University of Barcelona, Spain, Oscar Vilarroya, to let them run a study using magnetic resonance imaging (MRI) to measure the neuroanatomy of women before they became pregnant, and then again after they gave birth. Squeezed in alongside their main projects, the investigation took eight years and included dozens of participants. The results, published in 2016, were revelatory1. Two to three months after giving birth, multiple regions of the cerebral cortex were, on average, 2% smaller than before conception. And most of them remained smaller two years later. Although shrinkage might evoke the idea of a deficit, the team showed that the degree of cortical reduction predicted the strength of a mother’s attachment to her infant, and proposed that pregnancy prepares the brain for parenthood. Today, Carmona, now at the Gregorio Marañón Health Research Institute in Madrid, is one of several scientists uncovering how pregnancy and parenthood transform the brain. Elseline Hoekzema, one of Carmona’s passengers that evening in 2008, is another. In 2022, Hoekzema, who is now at the Amsterdam University Medical Centre in the Netherlands, confirmed that the cortical regions that shrink during pregnancy also function differently for at least a year after giving birth2. These studies and others, say researchers, highlight a transformational life event that has long been neglected by neuroscience — one that around 140 million women experience annually.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory and Learning
Link ID: 29418 - Posted: 08.02.2024

By Miryam Naddaf Researchers have identified neurons in the brains of baby mice that enable them to form a unique, strong bond with their mother in the first few days of life. Stimulating these neurons in mouse pups that had been separated from their mother could mimic the soothing effect of their mother’s presence, and reduced behaviours associated with stress. The findings, published today in Science1, offer fresh clues about the formation of the mother–infant bond in mammals, and could help researchers to better understand how brain development influences behaviour. “We know very little about how the brains of infants make sense of their social world,” says study co-author Marcelo Dietrich, a neurobiologist at Yale University in New Haven, Connecticut. “When I started my lab ten years ago, and I wanted to study this kind of stuff, people said it was delusional. It will fail. It’s too difficult.” Now, “we show that it’s possible: one can do rigorous science and try to understand these mechanisms that are potentially very important for development and health”. “I see these neurons as the ‘I feel good with mommy’ neurons,” says Catharine Dulac, a neuroscientist at the University of Harvard in Cambridge, Massachusetts. “The features that [they] discovered provide some framework to think about humans.” Bonding in the brain Dietrich and his team studied nursing mouse pups that were between 16 and 18 days old. They used live imaging techniques to record activity in the zona incerta (ZI), a thin layer of grey matter located below the thalamus, while the animals interacted with their mother. © 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: 29409 - Posted: 07.27.2024

By Phie Jacobs Is there really such a thing as a “male” or “female” brain? Sex certainly seems to affect a person’s risk of developing various psychiatric and other brain-related conditions—but scientists aren’t entirely sure why. Attention-deficit/hyperactivity disorder for example, is more commonly diagnosed in individuals who were assigned male at birth (AMAB), whereas those assigned female at birth (AFAB) are more likely to exhibit symptoms of anxiety. It’s unclear, however, whether these differences are actually driven by sex, or have more to do with how people are perceived and treated based on their sex or gender. Now, new research suggests sex and gender are associated with distinct brain networks. Published today in Science Advances, the findings draw on brain imaging data from nearly 5000 children to reveal that gender and sex aren’t just distinct from one another in society—they also play unique roles in biology. In science, the term “biological sex” encompasses a variety of genetic, hormonal, and anatomical characteristics. People are typically assigned “male” or “female” as their sex at birth, although the medical establishment in recent years has begun to acknowledge that sex doesn’t always fall neatly into binary categories. Indeed, about 0.05% of children born in the United States are assigned intersex at birth. Gender, by contrast, has more to do with a person’s attitudes, feelings, and behavior—and may not always align with the sex they were assigned at birth. These nuances often go unrecognized in neuroscience, says Sheila Shanmugan, a reproductive psychiatrist at the University of Pennsylvania who wasn’t involved in the new study. Sex and gender-based differences in the brain “have historically been understudied,” she explains, “and terms describing each are often conflated.” © 2024 American Association for the Advancement of Science.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 29393 - Posted: 07.13.2024

By Sara Reardon Specific nerve cells on the penis and clitoris detect vibrations and then become activated, causing sexual behaviours such as erections, a study in mice has revealed1. The findings could lead to new treatments for conditions such as erectile dysfunction, or for restoring sexual function in people with lower-body paralysis. Krause corpuscles — nerve endings in tightly wrapped balls located just under the skin — were first discovered in human genitals more than 150 years ago. The structures are similar to touch-activated corpuscles found on people’s fingers and hands, which respond to vibrations as the skin moves across a textured surface. But there is little research into how the genital corpuscles work and how they are involved in sex, probably because the topic is sometimes considered taboo. “It’s been hard to get people to work on this because some people have a hard time talking about it,” says David Ginty, a sensory neurobiologist at Harvard Medical School in Boston, Massachusetts, who led the team that conducted the latest research. “But I don’t, because the biology is so interesting.” Ginty and other sensory biologists have long wanted to study these mysterious neuron balls. But activating and tracking specific neurons was nearly impossible until advanced molecular techniques emerged in the past 20 years. In a 19 June paper in Nature1, Ginty and his collaborators activated the Krause corpuscles in both male and female mice using various mechanical and electrical stimuli. The neurons fired in response to low-frequency vibrations in the range of 40–80 hertz. Ginty notes that these frequencies are generally used in many sex toys; humans, it seems, realized that this was the best way to stimulate Krause corpuscles before any official experiments were published. © 2024 Springer Nature Limited

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 5: The Sensorimotor System
Link ID: 29365 - Posted: 06.24.2024

By Virginia Morell Leaping over waves or body surfing side by side, dolphins are a fun-loving bunch. But their frolicking—and that of species from hyenas to humans—has long baffled evolutionary biologists. Why expend so much energy on play? A new study offers an intriguing explanation: Juvenile male dolphins use play to acquire the skills required for fathering calves, researchers report today in the Proceedings of the National Academy of Sciences. Most significantly, the scientists found the most playful males go on to have more calves as adults. The study is likely to spur further research into play behavior in additional species, other scientists say. “It’s exciting research, and it solves an evolutionary puzzle,” says Jennifer Smith, a behavioral ecologist at the University of Wisconsin–Eau Claire. “This is the first study to link play behavior in the wild to reproductive success.” Since 1982, scientists have observed some 200 male Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the exceptionally clear waters of Shark Bay in Australia. About 20 years ago, the researchers noticed that young males, 4 to 12 years old, often played together as if they were herding a fertile female, flanking her on either side, while swimming in sync with each other and making popping vocalizations. This kind of “synchronicity is crucial for male reproduction,” says Kathryn Holmes, a behavioral biologist with the Shark Bay Dolphin Research project and lead author of the new study. The young dolphins’ behaviors were strikingly similar to those of the adults. “We wondered if this was ‘play practice’ for the adult behaviors,” Holmes says. So she and her colleagues closely tracked 28 juvenile males for 4 to 5 months over several years, recording their interactions and play behaviors. When socializing, the males “played almost continuously,” Holmes says. “They seemed to never tire of their games.” © 2024 American Association for the Advancement of Science.

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: 29353 - Posted: 06.11.2024

Sacha Pfeiffer A few weeks ago, at about 6:45 in the morning, I was at home, waiting to talk live on the air with Morning Edition host Michel Martin about a story I'd done, when I suddenly heard a loud metallic hammering. It sounded like a machine was vibrating my house. It happened again about 15 seconds later. And again after that. This rhythmic clatter seemed to be coming from my basement utility closet. Was my furnace breaking? Or my water heater? I worried that it might happen while I was on the air. Luckily, the noise stopped while I spoke with Michel, but restarted later. This time I heard another sound, a warbling or trilling, possibly inside my chimney. Was there an animal in there? I ran outside, looked up at my roof — and saw a woodpecker drilling away at my metal chimney cap. I've seen and heard plenty of woodpeckers hammer on trees. But never on metal. So to find out why the bird was doing this, I called an expert: Kevin McGowan, an ornithologist at the Cornell Lab of Ornithology who recently created a course called "The Wonderful World of Woodpeckers." McGowan said woodpeckers batter wood to find food, make a home, mark territory and attract a mate. But when they bash away at metal, "what the birds are trying to do is make as big a noise as possible," he said, "and a number of these guys have found that — you know what? If you hammer on metal, it's really loud!" Woodpeckers primarily do this during the springtime breeding season, and their metallic racket has two purposes, "basically summarized as: All other guys stay away, all the girls come to me," McGowan said. "And the bigger the noise, the better." © 2024 npr

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: 29333 - Posted: 06.02.2024

By Clay Risen Academic conferences are usually staid affairs, but the 1973 International Symposium on Gender Identity, held in Dubrovnik, Yugoslavia, was an exception. Everything was peaceful until a psychologist named John Money stood and yelled, “Mickey Diamond, I hate your guts!” Milton Diamond, a sexologist who had gone by Mickey since childhood, was sitting on the other side of the room. Dr. Money and Dr. Diamond were bitter rivals: Dr. Money, a nationally recognized researcher at Johns Hopkins University, had long argued that sexual and gender identity are neutral at birth and shaped primarily by an infant’s surroundings. Dr. Diamond, who was just beginning his career at the University of Hawaii, strongly disagreed, and had said so repeatedly — including in a widely read 1965 critique of Dr. Money’s work. He took particular issue with Dr. Money’s recommendation that intersex infants have surgery to “correct” their genitals. Dr. Money rushed over to Dr. Diamond, getting in his face, furiously insisting he was right. Dr. Diamond only replied, “The data is not there.” At one point, eyewitnesses reported that Dr. Money slugged Dr. Diamond, though Dr. Diamond later said he didn’t remember it. The incident, reported by the journalist John Colapinto in Rolling Stone magazine and in a subsequent book, “As Nature Made Him: The Boy Who Was Raised as a Girl” (2000), was especially heated because of a recent announcement by Dr. Money. He had been working with a child who in 1965, after his penis was irreparably damaged during a circumcision, had undergone further surgery to remove his male genitalia. The child was then raised as a girl, taking on all the conventional physical and emotional characteristics of a female adolescent — happily, Dr. Money said. Though the child was not born intersex, Dr. Money claimed that the case proved that gender and sexual identity were malleable and that intersex children should indeed receive surgery. © 2024 The New York Times Company

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 29297 - Posted: 05.09.2024

By Joshua Cohen In the U.S., 23 states have passed legislation to ban medicalized care for minors with gender dysphoria, or the experience of distress that can occur when a person’s gender identity does not match the sex they were assigned at birth. On the other hand, 12 state legislatures have introduced laws to protect access to youth transgender care. Such care can include puberty blockers, which are medications that suppress the body’s production of sex hormones, and cross-sex hormones like testosterone or estrogen that alter secondary sex characteristics. It also may include sexual reassignment surgery in rare instances. U.S. policies on both ends of the spectrum are not science-driven but rather emanate from polar-opposite ideologies. Unlike in Europe, there doesn’t appear to be room for a non-ideological process for determining what the best care is that weighs the emerging clinical evidence and adjusts policies accordingly. As reported in Axios, state efforts to restrict various forms of transgender medicine are being fueled by religious groups that aim to shape policy based on their strongly held beliefs around the immutability of gender and family. Faith-based objections to transgender care come from a worldview in which God created humans as male or female. Here, the role of parents’ rights features prominently, as well as a conviction that adolescents are insufficiently mature to decide on trans alterations to their bodies. Moreover, lawmakers point out that some young people later regret having had irreversible body-altering treatment. The bans on care can be driven by extreme religious views. In one example, The Associated Press reported last year that Oklahoma state Sen. David Bullard introduced what he called the “Millstone Act” — a bill that would make the act of providing gender transition procedures to anyone under the age of 26 a felony — by citing a Bible passage that suggests those who cause children to sin should be drowned. The age limit was later lowered to 18.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 29287 - Posted: 05.03.2024

In 2023, students protested against a new policy in Texas, where parents would be notified if their child asks to be identified as transgender.Credit: Brett Coomer/Houston Chronicle/Getty This week, Nature is launching a collection of opinion articles on sex and gender in research. Further articles will be published in the coming months. The series will highlight the necessity and challenges of studying a topic that is both hugely under-researched and, increasingly, the focus of arguments worldwide — many of which are neither healthy nor constructive. Some scientists have been warned off studying sex differences by colleagues. Others, who are already working on sex or gender-related topics, are hesitant to publish their views. Such a climate of fear and reticence serves no one. To find a way forward we need more knowledge, not less. Nearly 20 researchers from diverse fields, including neuroscience, psychology, immunology and cancer, have contributed to the series, which provides a snapshot of where scholars studying sex and gender are aligned — and where they are not. In time, we hope this collection will help to shape research, and provide a reference point for moderating often-intemperate debates. In practice, people use sex and gender to mean different things. But researchers studying animals typically use sex to refer to male and female individuals, as defined by various anatomical and other biological features. In studies involving humans, participants are generally asked to identify their own sex and/or gender category. Here, gender usually encompasses social and environmental factors, including gender roles, expectations and identity. © 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: 29281 - Posted: 05.02.2024

By Tim Vernimmen Most amphibians aren’t exactly doting parents — they just find a partner and release as many eggs or sperm as possible, in hopes that viable larvae will hatch from at least some fertilized eggs, and at least some of those larvae will survive to adulthood. Yet in as many as one in five amphibian species, one or both parents stick around to care for their offspring, using a staggering variety of strategies. The most well-known amphibian parents are the brightly colored poison frogs, a group of around 200 species that will repeatedly be leaping into view in this article. Yet their parenting skills may not be as exceptional as once thought, says biologist Jennifer Stynoski of the University of Costa Rica, who decided to study this group when she spotted them on a field trip as a student years ago. “I think they’ve just received a lot of attention because they’re so beautiful. They’re very cute to study.” So — what makes an exemplary amphibian parent? Much remains to be discovered, but some common principles have emerged. Stay away from the water Unlike reptiles and the birds that evolved from them, the ancestors of today’s amphibians never developed eggs with tough, watertight shells. This means their eggs need water to survive, as do the gilled larvae that usually come wriggling out. Yet the ponds in which many amphibians deposit their eggs are full of other animals, many eager to supplement their diet by slurping up a mouthful of eggs. “This must be one reason why so many species have evolved ways to lay their eggs away from the water,” says behavioral ecologist Eva Ringler of the University of Bern in Switzerland. © 2024 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: 29279 - Posted: 04.30.2024

Jon Hamilton A sibling can change your life — even before you're born. That's because when males and females share a womb, sex hormones from one fetus can cause lasting changes in the others. It's called the intrauterine position phenomenon, or intrauterine position effects, and different versions of it have been observed in rodents, pigs, sheep — and, probably, humans. "It's really kind of strange to think something so random as who you develop next to in utero can absolutely change the trajectory of your development," says Bryce Ryan, a professor of biology at the University of Redlands. The phenomenon is more than a scientific oddity. It helped establish that even tiny amounts of hormone-like chemicals, like those found in some plastics, could affect a fetus. Cattle breeders in ancient Rome may have been the first people to recognize the importance of a sibling's sex. They realized that when a cow gives birth to male-female twins, the female is usually sterile. These females, known as freemartins, also act more like males when they grow up. Scientists began to understand why in the early 1900s. They found evidence that hormones from the male twin were affecting the female's development. The effect is less obvious in other mammals, Ryan says. Female offspring in rodents, for example, can still reproduce, but they have measurable differences in sexual development and tend to be more aggressive. © 2024 npr

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: 29250 - Posted: 04.11.2024

By Gina Jiménez Being pregnant and giving birth changes a person’s brain, but the brain looks different depending on whether it’s examined during pregnancy or after a person gives birth, a recent study found. The research is helping disentangle some of the mysteries in the long-ignored field of maternal neuroscience. The study, published in January in Nature Neuroscience, followed more than 100 new mothers from near the end of their pregnancy until about three weeks on average after they had their baby. Previous research had examined birthing parents’ brain before they gave birth or during the postpartum period, but this study observed them both before and after birth, and it also took into account whether they had a vaginal birth or C-section. The findings reveal temporary changes in some brain regions and more permanent ones in a brain circuit that activates when people are not engaged in an active task and that is also involved in self-reflection and empathizing with others. The study has “ordered” some of the scientific disagreements in the field, says its senior author Susana Carmona, a neuroscience researcher now at Gregorio Marañón General University Hospital in Spain.* “It fills important gaps—that is why it’s novel,” says Joe Lonstein, a neuroscientist who studies animal parenting behaviors at Michigan State University but was not involved with the new paper. “There were things we just didn’t know about the timing of events.” Much of the scientific literature on pregnancy and postpartum neuroscience is only around a decade old. A 2016 study found that gray matter decreased in women after they had a baby for the first time, and the reductions persisted for at least six years after pregnancy. In contrast, other studies have observed that gray matter increases in the first weeks after people give birth. The new paper helps reconcile these results: the researchers found that women indeed lost gray matter during pregnancy and childbirth but got it back in most brain areas after they had their baby. © 2024 SCIENTIFIC AMERICAN,

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: 29197 - Posted: 03.19.2024

By Jake Buehler In the middle of the night in a humid coastal rainforest, a litter of pink, hairless babies snuggle with their mother. They stir and squeak for milk, their mother obliges, and they are sated. But these are no puppies or cubs. They are snake-shaped amphibians, far closer to frogs than foxes. These ringed caecilian moms feed their hatchlings a kind of “milk” brewed in the reproductive tract, researchers report in the March 8 Science. The long, cylindrical creatures are the first egg-laying amphibians known to feed hatchlings this way. The discovery suggests the evolution of parental care across animal life is more diverse than researchers thought. For an animal with so few discernable external features, caecilians are a fount of strange biology. Caecilians are elusive, legless, burrowing amphibians that are nearly blind (SN: 6/19/17). Some species, like the ringed caecilian (Siphonops annulatus) in the new study, have poisonous slime, may be venomous and feed their own skin to their young (SN: 7/3/20). Herpetologist Carlos Jared of the Instituto Butantan in São Paulo and his colleagues have been studying these eccentric animals for years. In previous studies, the team noticed that ringed caecilian hatchlings, which live their first two months out of the egg in their mother’s care, spent much of their time around the end of her body near the shared opening of the reproductive, digestive and urinary systems — an anatomical part called the vent. The female would periodically expel a thick fluid from the vent, which the young would enthusiastically feed on. “Some [young] even stuck their heads inside this opening,” Jared says. In the new work, the team collected 16 females and their newly hatched litters from Bahia state in Brazil, bringing them into the lab for observation. There, the researchers recorded the amphibians’ interactions, accumulating over 240 hours of video footage. The team recorded 36 feedings, which often involved the babies wriggling and nibbling at their mother’s vent while making high-pitched noises. Mom would then raise that end of her body and release the fluid. This happened up to six times per day and appeared to be in response to the babies’ pleas. © Society for Science & the Public 2000–2024.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 29188 - Posted: 03.09.2024

By Emily Anthes Colombia is a bird watcher’s paradise. Its stunningly diverse ecosystems — which include mountain ranges, mangrove swamps, Caribbean beaches and Amazonian rainforests — are home to more avian species than any other country on Earth. So when Hamish Spencer, an evolutionary biologist at the University of Otago in New Zealand, booked a bird-watching vacation in Colombia, he was hoping to spot some interesting and unusual creatures. He got more than he bargained for. During one outing, in early January 2023, the proprietor of a local farm drew his attention to a green honeycreeper, a small songbird that is common in forests ranging from southern Mexico to Brazil. But this particular green honeycreeper had highly unusual plumage. The left side of its body was covered in shimmering spring-green feathers, the classic coloring for females. Its right side, however, was iridescent blue, the telltale marker of a male. The bird appeared to be a bilateral gynandromorph: female on one side and male on the other. “It was just incredible,” Dr. Spencer said. “We were lucky to see it.” Gynandromorphism has been documented in a variety of birds, as well as insects, crustaceans and other organisms. But it’s a relatively rare and poorly understood phenomenon. The bird Dr. Spencer saw in Colombia is only the second known case of bilateral gynandromorphism in a green honeycreeper — and the first documented in the wild. © 2024 The New York Times Compan

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 29180 - Posted: 03.07.2024

Philip Hoare Whales are extraordinarily sensuous creatures. Those blubbery bodies are highly sensitive, and sensitised. At social meetings, pods of sperm, humpback and right whales will roll around one another’s bodies for hours at a time. I’ve seen a group of right whales engaged in foreplay and penetration lasting an entire morning. I have also watched a male-female couple so blissfully conjoined that they appeared unbothered by our little fishing boat as they passed underneath it. And in what may sound like a career of cetacean voyeurism, I have also been caught up in a fast-moving superpod of dusky dolphins continually penetrating each other at speed, regardless of the gender of their partner. That’s why this week’s report of the first scientifically documented male-to-male sexual interactions between two humpback whales off the coast of Hawaii is not surprising. The remarkable image of a two-metre whale penis entering another male “leaves little room for discussion that there is a sexual component to such behaviour”, as one whale scientist, Jeroen Hoekendijk at the Wageningen Marine Research institute in the Netherlands, notes drily. In fact, one of the whales was ailing and there has been speculation that the encounter may not have been consensual or that the healthy whale was actually giving comfort to the other. Whatever the truth, such “flagrant” acts also expose many of our human presumptions about sexuality, gender and identity. Off the north-west Pacific coast of the US, male orcas often leave family pods to rub their erections against each other’s bellies. But females have also reportedly been seen engaging in sexual contact with one another, too. © 2024 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: 29173 - Posted: 03.02.2024

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