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

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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.

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

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

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

By Meeri Kim A woman’s menstrual cycle is driven by the ebb and flow of hormones that prepare the body for pregnancy. This symphony of hormones not only transforms the reproductive organs, but, according to recent research, also reshapes the brain. Live well every day with tips and guidance on food, fitness and mental health, delivered to your inbox every Thursday. Two studies released in October performed detailed brain scans of women at multiple points across the menstrual cycle, finding that the volume or thickness of certain regions change in sync with hormone levels. The areas of the brain highlighted by both studies are those in the limbic system, a group of brain structures that govern emotions, memory and behavior. “It’s like the brain being on a roller coaster every 28 days or so, depending on the length of the cycle,” said Erika Comasco, associate professor of women and children’s health at Uppsala University in Sweden, who was not involved in the research. “The importance of these studies is that they are building knowledge about the impact of these hormonal fluctuations on how the brain is structured.” “These brain changes may or may not alter the way we actually act, think and feel in our everyday lives. So the important next steps for the science are to put those pieces of the puzzle together,” said Adriene Beltz, associate professor of psychology at the University of Michigan, who was also not involved in the research. “Do the hormonal effects on brain structure influence how the brain works?” How hormones drive the menstrual cycle During a woman’s period, which marks the beginning of the menstrual cycle, hormones are at low levels. But they rise dramatically over a few weeks. Estrogen levels in the blood become eight times higher at ovulation around Day 14, while progesterone levels increase by 80-fold approximately seven days later. The production of follicle-stimulating hormone prompts the growth of an ovarian follicle into a mature egg, while a surge of luteinizing hormone triggers the release of the egg.

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 29026 - 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

Keyword: Sexual Behavior; Evolution
Link ID: 29014 - Posted: 11.22.2023

By Azeen Ghorayshi Doctors and patients have long known that antidepressants can cause sexual problems. No libido. Pleasureless orgasms. Numb genitals. Well over half of people taking the drugs report such side effects. Now, a small but vocal group of patients is speaking out about severe sexual problems that have endured even long after they stopped taking selective serotonin reuptake inhibitors, the most popular type of antidepressants. The drugs’ effects have been devastating, they said, leaving them unable to enjoy sex or sustain romantic relationships. “My clitoris feels like a knuckle,” said Emily Grey, a 27-year-old in Vancouver, British Columbia, who took one such drug, Celexa, for depression from age 17 to 23. “It’s not a normal thing to have to come to terms with.” The safety label on Prozac, one of the most widely prescribed S.S.R.I.s, warns that sexual problems may persist after the drug is discontinued. And health authorities in Europe and Canada recently acknowledged that the medications can lead to lasting sexual issues. But researchers are only just beginning to quantify how many people have these long-term problems, known as post-S.S.R.I. sexual dysfunction. And the chronic condition remains contested among some psychiatrists, who point out that depression itself can curb sexual desire. Clinical trials have not followed people after they stop the drugs to determine whether such sexual problems stem from the medications. “I think it’s depression recurring. Until proven otherwise, that’s what it is,” said Dr. Anita Clayton, the chief of psychiatry at the University of Virginia School of Medicine and a leader of an expert group that will meet in Spain next year to formally define the condition. Dr. Clayton published some of the earliest research showing that S.S.R.I.s come with widespread sexual side effects. © 2023 The New York Times Company

Keyword: Depression; Sexual Behavior
Link ID: 28996 - Posted: 11.11.2023

By Bruce Bower Female chimps living in an East African forest experience menopause and then survive years, even decades, after becoming biologically unable to reproduce. The apes are the first known examples of wild, nonhuman primates to go through the fertility-squelching hormonal changes and live well beyond their reproductive years. The finding raises new questions about how menopause evolved, UCLA evolutionary anthropologist Brian Wood and colleagues conclude in the Oct. 27 Science. Until now, females who experience menopause and keep living for years have been documented only in humans and five whale species. It’s unclear what evolutionary benefit exists to explain such longevity past the point of being able to give birth and pass on one’s genes. Although evolutionary explanations for menopause remain debatable, the new finding reflects an especially close genetic relationship between humans and chimps, Wood says. “Both [species] are more predisposed to post-reproductive survival than other great apes.” Some evidence suggests that female fertility ends at similar ages in humans and chimps (Pan troglodytes) if our ape relatives live long enough, says anthropologist Kristen Hawkes of the University of Utah in Salt Lake City. But in other studies, female chimps, such as those studied by Jane Goodall at Tanzania’s Gombe National Park starting in 1960, aged quickly and often died in their early 30s, usually while still having menstrual cycles, she says. “What’s surprising [in Wood’s study] is so many females living so long after menopause,” Hawkes says. © Society for Science & the Public 2000–2023.

Keyword: Hormones & Behavior; Evolution
Link ID: 28975 - Posted: 10.28.2023

By Liz Fuller-Wright, The latest exploration of music in the natural world is taking place in Mala Murthy ’s lab at the Princeton Neuroscience Institute, where Murthy and her research group have used neural imaging, optogenetics, motion capture, modeling and artificial intelligence to pinpoint precisely where and how a fruit fly’s brain toggles between its standard solo and its mating serenade. Their research appears in the current issue of the journal Nature. “For me it is very rewarding that, in a team of exceptional scientists coming from different backgrounds, we joined forces and methodologies to figure out the key characteristics of a neural circuit that can explain a complex behavior — the patterning of courtship song,” said Frederic Römschied, first author on this paper and a former postdoctoral fellow in Murthy’s lab. He is now a group leader at the European Neuroscience Institute in Göttingen, Germany. “It might be a surprise to discover that the fruit flies buzzing around your banana can sing, but it’s more than music, it’s communication,” said Murthy, the Karol and Marnie Marcin ’96 Professor and the director of the Princeton Neuroscience Institute. “It’s a conversation, with a back and forth. He sings, and she slows down, and she turns, and then he sings more. He’s constantly assessing her behavior to decide exactly how to sing. They’re exchanging information in this way. Unlike a songbird, belting out his song from his perch, he tunes everything into what she’s doing. It’s a dialogue.” It might be a surprise to discover that the fruit flies buzzing around your banana can sing, but it’s more than music, it’s communication. By studying how these tiny brains work, researchers hope to develop insights that will prove useful in the larger and more complex brains that are millions of times harder to study. In particular, Murthy’s team is trying to determine how the brain decides what behavior is appropriate in which context. © 2023 The Trustees of Princeton University

Keyword: Animal Communication; Sexual Behavior
Link ID: 28959 - Posted: 10.14.2023

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

Keyword: Sexual Behavior
Link ID: 28956 - Posted: 10.12.2023