Chapter 8. Hormones and Sex

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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.

Keyword: Sexual Behavior
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

Keyword: Sexual Behavior
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

Keyword: Sexual Behavior
Link ID: 29173 - Posted: 03.02.2024

NIH-funded study shows prenatal mental health support is effective for women living in low-resource settings. Results from a large clinical trial funded by the National Institutes of Health show that an intervention for anxiety provided to pregnant women living in Pakistan significantly reduced the likelihood of the women developing moderate-to-severe anxiety, depression, or both six weeks after birth. The unique intervention was administered by non-specialized providers who had the equivalent of a bachelor’s degree in psychology—but no clinical experience. The results suggest this intervention could be an effective way to prevent the development of postpartum mental health challenges in women living in low-resource settings. “In low resource settings, it can be challenging for women to access mental health care due to a global shortage of trained mental health specialists,” said Joshua A. Gordon, M.D., Ph.D., Director of the National Institute of Mental Health, part of NIH. “This study shows that non-specialists could help to fill this gap, providing care to more women during this critical period." Led by Pamela J. Surkan, Ph.D., Sc.D.(link is external), of Johns Hopkins Bloomberg School of Public Health, Baltimore, the study was conducted in the Punjab Province of Pakistan between April 2019 and January 2022. Pregnant women with symptoms of at least mild anxiety were randomly assigned to receive either routine pregnancy care or a cognitive behavioral therapy (CBT)-based intervention called Happy Mother-Healthy Baby. The researchers assessed the participants (380 women in the CBT group and 375 women in the routine care group) for anxiety and depression six weeks after the birth of their child.

Keyword: Depression; Sexual Behavior
Link ID: 29165 - Posted: 02.27.2024

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.

Keyword: Sexual Behavior; 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

Keyword: Sexual Behavior; Evolution
Link ID: 29149 - Posted: 02.13.2024

By Matt Richtel For decades, eating disorders were thought to afflict mostly, if not exclusively, women and girls. In fact, until 2013, the loss of menstruation had long been considered an official symptom of anorexia nervosa. Over the last decade, however, health experts have increasingly recognized that boys and men also suffer from eating disorders, and they have gained a better understanding of how differently the illness presents in that group. A small but growing body of scientists and physicians have dedicated themselves to identifying the problem, assessing its scope and developing treatments. Recently, two of these experts spoke to The New York Times about how the disease is affecting adolescent boys, what symptoms and behaviors parents should look for, and which treatments to consider. Dr. Jason Nagata is a pediatrician at the University of California, San Francisco, who specializes in eating disorders; he is senior editor of the Journal of Eating Disorders and editor of the book “Eating Disorders in Boys and Men.” Dr. Sarah Smith is a child and adolescent psychiatrist at the University of Toronto who specializes in eating disorders; she was the lead author on a study published in JAMA Open Network in December that showed sharp increases in the rates of hospitalizations for boys with eating disorders. The medical and scientific understanding of eating disorders is changing and expanding. What happened? Dr. Smith: Historically, eating disorders have been conceptualized mostly as anorexia, which has been portrayed as an illness of adolescent females who want to lose weight for aesthetic reasons. Dr. Nagata: There’s increasing recognition, particularly in the last decade or so, that some people with body image dissatisfaction are not trying to lose weight at all. Some men and boys are trying to become large and muscular. In fact, one-third of teenage boys across the United States report that they’re trying to bulk up and get more muscular. And a subset of those may develop eating disorders or muscle dysmorphia that can lead to significant psychological distress and physical health complications. © 2024 The New York Times Company

Keyword: Anorexia & Bulimia; Sexual Behavior
Link ID: 29140 - Posted: 02.08.2024

By Sabrina Malhi Researchers have found a possible link between the common hormone disorder PCOS and cognitive decline later in life. PCOS, which stands for polycystic ovary syndrome, is the most common endocrine disorder among women ages 15 to 44. However, it is often underdiagnosed because many of its symptoms, including abnormal menstrual cycles and excess hair, can be attributed to other causes. The syndrome was first described in 1935 by American gynecologists Irving F. Stein and Michael L. Leventhal. They published a paper documenting a group of women with lack of periods, excess body hair and enlarged ovaries with multiple cysts. Their work helped identify and characterize PCOS as it is known today. Health experts hypothesize that genetic factors could contribute to the development of the condition, but the exact causes are still unknown. Here’s what to know about PCOS and its potential link to cognitive health. PCOS is a chronic hormonal disorder characterized by overproduction of androgens, which are typically considered male hormones. High androgen levels can lead to irregular menstrual cycles and fertility issues when excessively produced in women. In the United States, 6 to 12 percent of people assigned female at birth who are of reproductive age are affected by PCOS, according to data from the Centers for Disease Control and Prevention. The condition is associated with an increased risk of obesity, high blood pressure, high cholesterol and endometrial cancer. PCOS is also often linked to insulin resistance, which can result in elevated blood sugar levels and an escalated risk of Type 2 diabetes. The condition can contribute to various metabolic issues, including high blood pressure, excess abdominal fat, and abnormal cholesterol or triglyceride levels. People with PCOS face an elevated risk of developing cardiovascular problems, such as high blood pressure, high cholesterol levels and an increased risk of heart disease. A recent study in the journal Neurology found that people with PCOS performed lower than normal on a suite of cognitive tests.

Keyword: Hormones & Behavior; Learning & Memory
Link ID: 29132 - Posted: 02.06.2024

By Sara Reardon Lustful male marsupials sacrifice their sleep for weeks to make more time for mating1. The antechinus, an Australian marsupial roughly the size of a gerbil, is a rare example of a mammal that mates during a certain season and never again. Roughly every August, male antechinus enter a three-week breeding frenzy in which they mate with every female they can and then die en masse. “It’s very short, very intense,” says zoologist Erika Zaid at La Trobe University in Melbourne, Australia. Males generally live for only one year; females can live for at least a year longer and produce more than one litter. To find out how males make enough time for sex in their short lives, Zaid and her colleagues trapped ten male and five female dusky antechinus (Antechinus swainsonii) and kept them in separate enclosures so they couldn’t mate. They attached activity monitors to the animals’ collars and collected blood samples to measure biomarkers. The researchers found that captive males, but not females, moved around much more and slept less during breeding season than they did the rest of the year. On average, the males’ sleep time per day was around 20% lower during the breeding season than during the non-breeding season ― and one male’s sleep time per day was more than 50% lower. At the end of breeding season, two of the males died within a few hours of one another. The other eight became sterile. To determine whether sleep loss occurs in the wild, Zaid and her colleagues trapped 38 animals from a related species called agile antechinus (A. agilis) before and during breeding season and measured the animals’ oxalic acid, a chemical in the blood whose levels drop when an animal is short on sleep. Males’ oxalic acid levels fell sharply during the breeding season. Unlike the captive females, wild females showed drops as well, suggesting that males were waking them up for shenanigans. Mysterious death © 2024 Springer Nature Limited

Keyword: Sleep; Sexual Behavior
Link ID: 29113 - Posted: 01.27.2024

By Sandra G. Boodman On the day after Christmas 2021, Abigail Aguilar, 18, and nearly three months pregnant, walked into her mother’s bedroom and in a flat, emotionless voice announced, “Mom, I’m going to slit my throat.” For weeks Quintina Sims had grappled with her daughter’s increasingly bizarre and frightening behavior. Aguilar had also been plagued by unremitting nausea, splitting headaches and weakness so severe her stepfather sometimes had to carry her to the bathroom. Doctors had largely brushed off her symptoms as the normal manifestations of early pregnancy. Aguilar’s threat triggered a cascade of events that would end in a hospital 130 miles south of her Kern County, Calif., home where doctors mobilized in an effort to discover what was making the previously healthy teenager so sick. After treatment after treatment failed, Sims, now 42, would be called upon to make what she called “the hardest decision of my life” — one that appears to have saved her daughter. Aguilar, who will turn 21 in a few weeks, is now working full time as a preschool teacher’s assistant and studying child development at a community college. She remembers very little of her harrowing six-week stay at Loma Linda University Medical Center, but says the months she spent recovering proved to be clarifying. “It made me realize that I had to value my life a lot more,” Aguilar said. “And I learned that my family was always going to be there for me.” An unexpected surprise In the fall of 2021, Aguilar, a recent high school graduate, was living with her grandparents in Los Angeles, working in a movie theater and going to college part time. In October, she discovered she was pregnant; the baby was due in July 2022. “It was a surprise,” she recalled. Aguilar, who was unmarried, struggled with what to do. She decided to have the baby, a decision her mother supported. “At first everything was fine,” Aguilar said.

Keyword: Schizophrenia; Hormones & Behavior
Link ID: 29112 - Posted: 01.23.2024

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

Keyword: Sexual Behavior; Evolution
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

Keyword: Sexual Behavior
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

Keyword: Sexual Behavior; Evolution
Link ID: 29095 - Posted: 01.13.2024

Pam Belluck A research team analyzed records of nearly a million women in Sweden’s national medical registries from 2001 through 2017, comparing 86,551 women who had perinatal depression with 865,510 women who did not. The groups were matched by age and year they gave birth. In two studies, the team found that depression that begins in pregnancy or soon after can have troubling implications for as long as 18 years. One study, published on Tuesday in JAMA Network Open, found that women with perinatal depression had three times the risk of suicidal behavior, defined as attempted or completed suicide, than women who did not experience perinatal depression. Risks were greatest in the year following their diagnosis, but, while they lessened over time, years later the risks were still twice as high compared with women without the disorder. The other study, published on Wednesday in BMJ, found that women with perinatal depression were more than six times at risk of dying by suicide as those without that diagnosis. The number of suicides was small, but it accounted for a large share of the deaths of women diagnosed with perinatal depression: 149 of the 522 deaths in that group, or 28.5 percent. For women without perinatal depression, there were 117 suicides out of 1,568 deaths or 7.5 percent. Suicide was a major reason women with perinatal depression were twice as likely to die from any cause over the 18-year period of the study compared with women without the disorder. The researchers also compared more than 20,000 women with perinatal depression to their biological sisters who gave birth during the same time frame and did not have the disorder. The risk of suicidal behavior for the sisters with perinatal depression was nearly three times that of their sisters without the diagnosis — almost as high as the difference between women with the illness and those without it to whom they were not related. That suggests depression plays a greater role in these outcomes than genetics or childhood environment, the researchers wrote. © 2024 The New York Times Company

Keyword: Depression; Hormones & Behavior
Link ID: 29089 - Posted: 01.11.2024

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.

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 29080 - Posted: 01.06.2024

Ian Sample Science editor Human tears carry a substance that dampens down aggression, according to researchers, who believe the drops may have evolved over time to protect wailing babies from harm. Sniffing emotional tears from women reduced male aggression by more than 40% in computerised tests, and prompted corresponding changes in the brain, though the scientists behind the study think all human tears would have a similar effect. “The reduction in aggression was impressive to us, it seems real,” said Noam Sobel, a professor of neurobiology at the Weizmann Institute of Science in Israel. “Whatever is in tears actually lowers aggression.” Charles Darwin puzzled over the point of weeping. Writing in The Expression of Emotions in Man and Animals in 1872, the great naturalist declared sobbing as “purposeless as the secretion of tears from a blow outside the eye”. But in the 150 years since, researchers have proposed all manner of roles, from signalling vulnerability and helplessness to clearing bacteria from the eyes. Previous work at Sobel’s lab found that sniffing women’s tears reduced male testosterone but it was unclear whether this affected behaviour. In animals, the picture is clearer: subordinate mole rats, for example, cover themselves in tears to protect themselves from aggressors. For the latest study, Dr Shani Agron and others in Sobel’s lab collected tears rolling down women’s faces as they watched sad movies. The researchers did not specifically advertise for female tear donors but nearly all who came forward were women, of whom six were selected because they produced tears in such quantities. The experiments involved 31 men who sniffed either saline or women’s tears before having swabs dabbed with the droplets stuck to their upper lip. The men then took part in a computerised game used in psychology to provoke aggressive behaviour by unfairly deducting players’ points. © 2023 Guardian News & Media Limited

Keyword: Aggression; Chemical Senses (Smell & Taste)
Link ID: 29063 - Posted: 12.22.2023

By Joseph Howlett Garter snakes have something in common with elephants, orcas, and naked mole rats: They form social groups that center around females. The snakes have clear “communities” composed of individuals they prefer hanging out with, and females act as leaders that tie the groups together and guide their members’ movements, according to the most extensive field study of snake sociality ever carried out. “This is an important first step in understanding how a community of snakes is organized in the wild,” says Gordon Burghardt, an ecologist at the University of Tennessee, Knoxville, who was not involved in the research. Other experts agree: “This is a big deal,” says integrative biologist Robert Mason of Oregon State University. “It’s a whole new avenue of research that I don’t think people have really given any thought to.” Ecologists had long assumed snakes are antisocial loners that hang out together only for core functions such as mating and hibernation. However, in 2020, Morgan Skinner, a behavioral ecologist at Wilfrid Laurier University, and collaborators showed in laboratory experiments that captive garter snakes have “friends”—specific snakes whose company they prefer over others. Still, studies of wild snakes were lacking “because they’re so secretive and difficult to find,” Skinner says. Then he learned that the Ontario Ministry of Transportation had funded an unprecedented long-term study of a huge population of Butler’s garter snakes (Thamnophis butleri) in Windsor, Canada. Ecologists began to monitor the flute-size slitherers in 2009 to keep them safe from nearby road construction. They regularly captured snakes in the 250-hectare study area, using identifying markings to track more than 3000 individuals over a 12-year span—about the lifetime of a garter snake. “We were mainly monitoring the population after they were relocated, to make sure they were thriving,” says Megan Hazell, a biologist with the consulting firm WSP, who led the field research as a graduate student at Queen’s University.

Keyword: Evolution; Sexual Behavior
Link ID: 29050 - Posted: 12.16.2023

By Carl Zimmer Why do we grow old and die? In the 19th century, the German biologist August Weismann argued that the machinery of life inevitably wore out with time. Death had evolved “for the need of the species,” he declared. It cleared away weak, old individuals so they wouldn’t compete with young ones. That explanation never made sense to George Williams, an American evolutionary biologist. Natural selection acts only on the genes that are passed down from one generation to the next. What happens at the end of an animal’s life can have no effect on the course of evolution. It occurred to Williams that growing old might instead be an inescapable side effect of natural selection. In 1957, he proposed a new theory: Genetic mutations that increased an animal’s fertility could also cause harm late in life. Over many generations, those mutations would create a burden that would lead eventually to death. A new study, published on Friday in the journal Science Advances, bolsters Williams’s theory using a trove of human DNA. Researchers found hundreds of mutations that could boost a young person’s fertility and that were linked to bodily damage later in life. Smaller studies in the past had already offered some support for Williams’s theory. In 2007, for example, a team of researchers studying a tiny worm found a pair of mutations that lengthened the creature’s life while cutting down its average number of offspring. But Jianzhi Zhang, an evolutionary biologist at the University of Michigan, was not satisfied with these experiments. “These are case studies,” he said. “We don’t know if in the entire genome there are lots of such mutations.” Dr. Zhang tapped into the UK Biobank, a database containing genetic material from half a million volunteers in Britain, along with information on their health and life experiences. The biobank has permitted scientists to uncover subtle links between genetic variations and thousands of traits such as high blood pressure, schizophrenia and a habit of smoking. Working with Dr. Erping Long, a medical researcher now at the Chinese Academy of Sciences, Dr. Zhang pored over the database for information about reproduction and longevity. The scientists found that the genetic variations linked to fertility, such as the number of children a volunteer had, were also linked to a shorter life span. © 2023 The New York Times Company

Keyword: Development of the Brain; Evolution
Link ID: 29048 - Posted: 12.16.2023

Maria Godoy What do you do when you can't get your kids to settle down to go to sleep? For a growing number of parents, the answer is melatonin. Recent research shows nearly one in five school-age children and adolescents are now using the supplement on a regular basis. Pediatricians say that's cause for alarm. "It is terrifying to me that this amount of an unregulated product is being utilized," says Dr. Cora Collette Breuner, a professor of pediatrics at the University of Washington. Melatonin is a hormone produced by your brain that helps regulate sleep-wake cycles. It's also sold as a dietary supplement and is widely used as a sleep aid. Sponsor Message Lauren Hartstein, a postdoctoral researcher who studies sleep in early childhood at the University of Colorado, Boulder, says she first got an inkling of melatonin's growing use in children and adolescents while screening families to participate in research. "All of a sudden last year, we noticed that there was a big uptick in the number of parents who were regularly giving [their kids] melatonin," Hartstein says. Hartstein and her colleagues wanted to learn more about just how widely melatonin is being used in kids. So they surveyed the parents of nearly 1,000 children between the ages of 1 to 14 across the country. She was surprised by just how many kids are taking the supplement. "Nearly 6% of preschoolers, [ages] 1 to 4, had taken it, and that number jumped significantly higher to 18% and 19% for school-age children and pre-teens," she says. As Hartstein and her co-authors recently reported in the journal JAMA Pediatrics, most of the kids that were using melatonin had been on it for a year or longer. And 1 in 4 kids were taking it every single night. © 2023 npr

Keyword: Biological Rhythms; Sleep
Link ID: 29047 - Posted: 12.16.2023

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

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 29029 - Posted: 12.02.2023