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

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As we open computers to connect with each other remotely, motor neurons in our spinal cord are opening synaptic pathways to connect with our muscles physically. We rarely think about these electrical signals passing back and forth between computers or our neurons and muscles, until those signals are lost. Kennedy’s disease, a neuromuscular degenerative disease, affects 1 in 40,000 men every year. Little progress has been made in understanding its biological basis since it was identified in the 1960s, but one promising lead may be a family of proteins known as neurotrophic factors. MSU scientists Cynthia Jordan, professor in the College of Natural Science Neuroscience Program, and Katherine Halievski, former Ph.D. student in Jordan’s Lab and lead author, published a benchmark study in the Journal of Physiology describing the key role of one of these proteins in Kennedy’s disease: Brain-Derived Neurotrophic Factor (BDNF). “There were stories that neurotrophic factors could slow down neurodegenerative diseases, but where they fell short was really understanding how they slow down the disease,” Jordan explained. “Where this paper and Katherine’s work stand alone is in using classic neuroscience techniques to understand how BDNF improved neuromuscular function at the cellular level.” Motor neurons are cells that carry signals from the brain to every muscle in the body — fast twitch muscles that perform quick, high impact movements such as jumping, and slow-twitch muscles that sustain long contractions such as standing. At each step in the pathway — from the neuron, along the synaptic pathway and to the muscle — BDNF supports the process, giving both neurons and muscles what they need to connect, survive and thrive. © Michigan State University

Keyword: Movement Disorders; Hormones & Behavior
Link ID: 27320 - Posted: 06.24.2020

By Elizabeth Preston A clown fish uses his fins to fan water across a glistening mass of eggs, keeping them aerated. A silver arowana scoops up his fertilized eggs with his mouth and holds them gently for two months, until a host of miniature adults swims free from his jaws. A seahorse drifts through coral, his belly pouch swollen with unborn young. Most fish are uninvolved parents. They dump their eggs and sperm, then swim off and let nature take its course. But some species of fish take their parental duties more seriously — and among them, the majority of caring parents are dads. Care from mothers, or from both parents at once, is much less common. In a study published last fall in Evolution, researchers found evidence that paternal care, the system in which dads are the sole caretakers, has evolved dozens of times in fish. These fish aren’t exactly helicopter dads. Their most common parenting style is simply guarding eggs after they’re fertilized. “Some people are surprised this is considered care,” said Frieda Benun Sutton, an evolutionary biologist at the City University of New York. But it does count. To learn more about why this type of care in fish usually comes from dads, Dr. Benun Sutton and her co-author, Anthony Wilson, of Brooklyn College, took a deep dive into the family history of fish parents. They started with an evolutionary tree, built by other researchers in 2017 using genetic data, that shows how almost 2,000 fish species are related. Then they mapped onto the tree all the information they could find about parental care in those species: Were young cared for by fathers, mothers, both or nobody? They also added other factors including the size and number of each fish’s eggs and how they’re fertilized. The completed tree showed that care by fathers is no evolutionary accident: It has arisen at least 30 separate times. Hundreds of the species in this sample have absent mothers and caring fathers. But why? © 2020 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 27316 - Posted: 06.22.2020

By Bethany Brookshire Biomedical science has historically been a male-dominated world — not just for the scientists, but also for their research subjects. Even most lab mice were male (SN: 6/18/19). But now, a new study shows that researchers are starting to include more females — from mice to humans — in their work. In 2019, 49 percent of articles surveyed in biomedical science used both male and female subjects, almost twice as many as a decade before, according to findings published June 9 in eLife. A study of articles published in 2009 across 10 biomedical disciplines showed a dismal picture. Only 28 percent of 841 research studies included both males and female subjects. The results were published in 2011 in Neuroscience and Biobehavioral Reviews. The scientific world took note. In 2016, the U.S. National Institutes of Health instituted the Sex as a Biological Variable policy in an effort to correct the imbalance. Scientists had to use both males and females in NIH-funded research unless they could present a “strong justification” otherwise. Annaliese Beery, a neuroscientist at Smith College in Northhampton, Mass., conducted the original study showing the extent of sex bias in research. In 2019, she and Nicole Woitowich, a chemist at Northwestern University in Evanston, Ill., wanted to see if sex bias was still as strong as it was in 2009. Have things improved? After scanning another 720 articles across nine of the 10 original disciplines, the researchers have shown that yes, they have, with nearly half of all journal articles including both males and females. Behavioral research was the most inclusive, with both sexes in 81 percent of studies. Overall, six out of nine fields surveyed showed a significant increase in studies that included both sexes. © Society for Science & the Public 2000–2020

Keyword: Sexual Behavior
Link ID: 27297 - Posted: 06.10.2020

By Yasmin Anwar, Media Relations Stephen Glickman, a pioneer in behavioral endocrinology and founder of the world’s first colony of captive spotted hyenas — he raised generations of them in a UC Berkeley research facility — died at his home in Berkeley on May 22 from pancreatic cancer. He was 87. A professor emeritus of psychology and of integrative biology, whose lifelong bond with animals began during his boyhood near the Bronx Zoo in New York, Glickman joined the UC Berkeley faculty in 1968. Over the next five decades, he conducted studies of creatures great and small, authoring more than 100 research papers. His sharp intellect, warm wit and overall lovability engaged peers and protégés in scientific and social justice pursuits, colleagues said. “Steve was a giant in the field of animal behavior,” said UC Berkeley psychology chair Ann Kring. “He studied a wide variety of species in the wild, at the zoo and, perhaps most famously, at the field station where he conducted work with hyenas for more than 30 years.” Glickman’s standout legacy is his ardent stewardship of a colony of spotted hyenas at UC Berkeley’s Field Station for the Study of Behavior, Ecology and Reproduction. The hyena compound in the Berkeley hills, above the campus, closed in 2014 when funding dried up, but not before yielding seminal discoveries about endocrinology, fertility and other medical conditions that affect humans. Hormone-driven matriarchy By studying female hyenas, who use a long, phallic clitoris, instead of a vagina, for mating and giving birth, Glickman and fellow researchers found that high levels of androgens produced in their ovaries masculinized their sex organs and boosted their aggression and dominance in the pack. Copyright © 2020 UC Regents; all rights reserved

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 27292 - Posted: 06.09.2020

By Meredith Wadman In January, one of the first publications on those sickened by the novel coronavirus in Wuhan, China, reported that three out of every four hospitalized patients were male. Data from around the world have since confirmed that men face a greater risk of severe illness and death from COVID-19 than women and that children are largely spared. Now, scientists investigating how the virus does its deadly work have zeroed in on a possible reason: Androgens—male hormones such as testosterone—appear to boost the virus’ ability to get inside cells. A constellation of emerging data supports this idea, including COVID-19 outcomes in men with prostate cancer and lab studies of how androgens regulate key genes. And preliminary observations from Spain suggest that a disproportionate number of men with male pattern baldness—which is linked to a powerful androgen—end up in hospitals with COVID-19. Researchers are rushing to test already approved drugs that block androgens’ effects, deploying them early in infection in hopes of slowing the virus and buying time for the immune system to beat it back. “Everybody is chasing a link between androgens … and the outcome of COVID-19,” says Howard Soule, executive vice president at the Prostate Cancer Foundation, who on 13 May ran a Zoom call presenting the newest research that drew 600 scientists and physicians. A second call scheduled for today will discuss incipient clinical trials. Epidemiological data from around the world have confirmed the early reports of male vulnerability. In Lombardy in Italy, for example, men comprised 82% of 1591 patients admitted to intensive care units (ICUs) from 20 February to 18 March, according to a JAMA paper. And male mortality exceeded that of women in every adult age group in another JAMA study of 5700 New York City patients hospitalized with COVID-19. © 2020 American Association for the Advancement of Science.

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 27284 - Posted: 06.04.2020

By Nicholas Bakalar Women who take benzodiazepines, such as Valium or Xanax, before becoming pregnant may be at increased risk for ectopic pregnancy, a new study found. An ectopic, or tubal, pregnancy is one in which a fertilized egg grows outside the uterus, often in a fallopian tube, and it is a life-threatening event. The egg must be removed with medication or surgery. Benzodiazepines, sold by prescription under several brand names, are widely prescribed for anxiety, sleep problems and seizures. The study, in Human Reproduction, used an insurance database of 1,691,366 pregnancies to track prescriptions for benzodiazepines in the 90 days before conception. Almost 18,000 of the of the women had used the drugs, and the scientists calculated that these women were 47 percent more likely to have a tubal pregnancy than those who did not. The study controlled for other risks for tubal pregnancy, including sexually transmitted infections, pelvic infection, use of an intrauterine device, smoking and fertility treatments. “Women planning a pregnancy who are using these drugs should talk to their care provider to see whether a change in treatment is possible, and then slowly change treatment before going off their contraceptive,” said the lead author, Elizabeth Wall-Wieler, a postdoctoral fellow at Stanford University. “Women for whom there is no alternative, or who have an unplanned pregnancy, should let their care provider know, and those pregnancies should be monitored carefully. The key to treating ectopic pregnancy is to treat it early.” © 2020 The New York Times Company

Keyword: Drug Abuse; Sexual Behavior
Link ID: 27278 - Posted: 06.04.2020

by Marcus A. Banks Brain structures differ in volume depending on a person’s social environment and socioeconomic status, and between men and women, according to a new analysis1. The findings could help explain differences seen in the brains of autistic women and men, many of whom find social communication challenging. Researchers analyzed brain scans from about 10,000 people enrolled in the UK Biobank, a large-scale initiative to understand health trends in the United Kingdom. The participants were 55 years old, on average. They completed surveys, answering questions about their income level, satisfaction with friends and family, participation in social activities and feelings of loneliness. The researchers found that associations between the survey responses and the volume of brain regions linked to social contact differ by sex. For example, women who live with two or more people have a larger amygdala — a brain region involved in decision-making and emotional responses — than do women from smaller households. By contrast, household size has little effect on the size variation of amygdalae among men. The study appeared 18 March in Science Advances. The scans also showed that men who say they lack social support from siblings and friends tend to have a larger nucleus accumbens, part of the brain’s reward circuitry, than men who reported having more social support. The researchers did not see this difference in women. Other differences between men and women appeared in networks involving multiple brain regions, such as those involved with visual processing. © 2020 Simons Foundation

Keyword: Sexual Behavior; Brain imaging
Link ID: 27260 - Posted: 05.21.2020

Dana Najjar The old riddle, “Which came first, the chicken or the egg?” is relatively easy to answer as a question about the evolution of birth in animals. Egg laying almost certainly came before live birth; the armored fish that inhabited the oceans half a billion years ago and were ancestral to all land vertebrates seem to have laid eggs. But the rest of the story is far from straightforward. Over millennia of evolution, nature has come up with only two ways for a newborn animal to come into the world. Either its mother lays it in an egg, where it can continue to grow before hatching, or it stays inside its mother until emerging as a more fully formed squirming newborn. “We have this really fundamental split,” said Camilla Whittington, a biologist at the University of Sydney. Is there some primordial reason for this strict reproductive dichotomy between egg laying (oviparity) and live birth (viviparity)? When and why did live birth evolve? These are just some of the questions that new research — including studies of a remarkable lizard that can lay eggs and bear live young at the same time — is exploring, all the while underscoring the enormous complexity and variability of sexual reproduction. Early female animals laid eggs in the sense that they released their ova into the world, often thousands at a time. Sperm released by males then fertilized some of these eggs in a hit-or-miss fashion, and the resulting embryos took their chances on surviving in the hostile world until they hatched. Many creatures, particularly small, simple ones, still reproduce this way. All Rights Reserved © 2020

Keyword: Sexual Behavior; Evolution
Link ID: 27257 - Posted: 05.20.2020

By Katherine Ellison After a lifetime of arriving late, missing deadlines and having friends call her a ditz, Leslie Crawford wanted to know whether her chronic distraction meant she had attention-deficit/hyperactivity disorder, ADHD. And, if that were true, could medication help? Over three visits with her managed-care plan doctor in San Francisco, Crawford, 57, a busy mother of two and professional editor, complied with urine and blood tests some doctors require to rule out drug abuse, and was checked for any preexisting heart condition that might make stimulants too risky. Then came the last step: a telephone interview. “What kind of student were you in elementary school?” she remembers the psychiatrist asking. “I was an A student,” Crawford answered. “I’m sorry,” he said, as Crawford recalled. “You don’t meet the qualification for ADHD and we can’t give you medication.” AD “I couldn’t believe it,” Crawford said later. Two private therapists had already told her she had ADHD, she said. But her plan’s psychiatrist said it was company policy to deny diagnosis and medication if a patient had done well in school as a child. This left Crawford with the option of paying several hundred dollars for a private psychiatrist’s evaluation, plus recurring costs for new prescriptions over time. For now, she’s not pursuing that. After her three appointments, “I just felt exhausted,” she said. ADHD affects more than 16 million U.S. children and adults. Despite decades of research involving thousands of studies, it remains one of the most perplexing of mental health diagnoses, susceptible to confusion and controversy even among doctors who treat it. The muddle can be particularly damaging to girls and women, who like Crawford may miss early treatment that could have spared them years of shame, anxiety, depression, self-harm and even suicide attempts.

Keyword: ADHD; Sexual Behavior
Link ID: 27252 - Posted: 05.18.2020

By Kim Severson In the 1980s, when marriage and adopting children seemed impossible dreams for gay men, the psychoanalyst Richard C. Friedman became their champion. His 1988 book, “Male Homosexuality: A Contemporary Psychoanalytic Perspective,” showed that sexual orientation was largely biological and presented a case that helped undermine the belief held by most Freudian analysts at the time that homosexuality was a pathology that could somehow be cured. “I felt an ethical obligation to find the reasons for anti-homosexual prejudice,” he once told an interviewer. His wife, Susan Matorin, a clinical social worker at the Weill Medical College of Cornell, put it more plainly: “Straight people had the same personality issues, and they got away with murder, but gay people were stigmatized, and he didn’t think that was right.” Dr. Friedman’s motivation wasn’t political. “He very much felt like you followed the science, and it didn’t matter what the political backdrop was,” his son, Jeremiah, a screenwriter in Los Angeles, said in a phone interview. Although the American Psychiatric Association, the dominant mental health organization in the United States, changed its diagnostic manual in 1973 and stopped classifying homosexuality as an illness, psychoanalysts continued to describe homosexuality as a perversion, and many believed it could be cured. Dr. Friedman, using studies of identical twins and theories of developmental psychology, made a scholarly rather than ideological case that biology rather than upbringing played a significant role in sexual orientation. It was a direct challenge to popular Freudian theories and thrust him into the center of debates among the more established heavyweights of psychoanalysis. It led to a model in which analyst and patient simply assumed that homosexuality was intrinsic, said Jack Drescher, a professor of psychiatry at Columbia University who knew Dr. Friedman and would later offer his own critiques of Dr. Friedman’s theory as new approaches to working with gay and lesbian patients emerged. © 2020 The New York Times Company

Keyword: Sexual Behavior
Link ID: 27229 - Posted: 05.05.2020

Christie Wilcox Sex might be biology’s most difficult enigma. The downsides of relying on sex to reproduce are undeniable: It takes two individuals, each of whom gets to pass on only part of their genome. Because these individuals generally have to get fairly intimate, they make themselves vulnerable to physical harm or infections from their partner. Asexual reproduction, or self-cloning, has none of these disadvantages. Clones can be made anywhere and anytime, and they receive the full complement of an individual’s genes. Yet despite all its benefits, asexual reproduction is the exception, not the norm, among organisms that have compartmentalized cells (eukaryotes). In plants, for example — which are somewhat known for their genetic flexibility — less than 1% of species are thought to reproduce asexually often. Among animals, only one out of every thousand known species is exclusively asexual. For centuries, biologists have pondered this apparent paradox. In 1932, the geneticist Hermann Muller, whose work on radiation-induced mutations would eventually garner a Nobel Prize, believed he had the answer. “Genetics has finally solved the age-old problem of the reason for the existence (i.e., the function) of sexuality and sex,” he boasted in The American Naturalist. He went on to explain, “Sexuality, through recombination, is a means for making the fullest use of the possibilities of gene mutations.” All Rights Reserved © 2020

Keyword: Sexual Behavior; Evolution
Link ID: 27210 - Posted: 04.24.2020

By Elizabeth Pennisi Ring-tailed lemurs have a peculiar habit of shaking their tails at potential rivals. New research shows that during the breeding season, a male’s trembling tail may instead be whisking sexy odors toward potential mates. The work is still preliminary, but chemical analyses have revealed the odor is a mixture of three chemicals that seem to pique a female’s interest. The new work “calls attention to the often underappreciated fact” that odors play an important role in primate societies, says Peter Kappeler, a primatologist at the University of Göttingen. Insects often use behavior-altering odors called pheromones to attract mates. So do mice. But biochemist Kazushige Touhara at the University of Tokyo wanted to know whether primates—including humans—use them as well. Some researchers say yes, but the existence of such “sex attractants” remains controversial. Ring-tailed lemurs (Lemur catta), named for their fluffy gray and black tails, are unusual among their fellow primates. Males have glands on their wrists that produce chemicals that quickly vaporize when exposed to air—similar to pheromones. They rub their wrists on their tails to transfer the odors before they vaporize, then shake their tails to broadcast the scent. For most of the year, these lemurs make bitter, leathery smelling chemicals used to keep other males at bay. But during the breeding season, they instead emit a sweet scent, Touhara says. He and his colleagues collected these secretions from the wrist glands with a tiny pipette and analyzed the chemical components. © 2020 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Chemical Senses (Smell & Taste)
Link ID: 27203 - Posted: 04.17.2020

By John Pickrell Joseph Schubert spends hours at a time lying in the dirt of the Australian outback watching for tiny flickers in the sparse, ground-hugging foliage. The 22-year-old arachnologist is searching for flea-sized peacock spiders, and he admits, he’s a little obsessed. But it wasn’t always so. Schubert grew up fearing spiders, with parents who were “absolutely terrified” of the eight-legged crawlers. “I was taught that every single spider in the house was going to kill me, and we should squish it and get rid of it,” he says. Then Schubert stumbled across some photographs of Australia’s endemic peacock spiders, a group named for the adult males’ vivid coloring and flamboyant dance moves aimed at wooing a mate (SN: 9/9/16; SN: 12/8/15). And he was hooked. “They raise their third pair of legs and dance around and show off like they are the most amazing animals on the planet, which in my eyes they are.” He decided to pursue a career in arachnology. And despite not quite having completed his undergraduate degree in biology, he’s begun working part time at Museums Victoria in Melbourne, and has already made a mark. Of the 86 known peacock spider species — each just 2.5 to 6 millimeters in length — 12 have been described by Schubert, including seven named in the March 27 Zootaxa. Those seven were found at a range of sites across Australia, including the barren dunes and shrublands of Victoria state’s Little Desert and the red rocks and arid outback gorges of Kalbarri National Park, north of Perth. © Society for Science & the Public 2000–2020

Keyword: Sexual Behavior; Evolution
Link ID: 27202 - Posted: 04.17.2020

By Elizabeth Pennisi Males resort to all sorts of desperate measures when fertile females are scarce, including banding together to guard a potential mate. Now, researchers have discovered that such bands of bottlenose dolphins may coordinate their actions with unique “popping” calls—the first evidence that animals other than humans can synchronize themselves using vocal signals. Humans often use vocal signals to coordinate actions, like marching and dancing, that reinforce unity and intimidate outside groups. The synchronized displays of other animals—like fireflies that light up at the same time—are thought to be competitive, showing off which male is the sexiest, rather than cooperative. In Shark Bay, off the coast Western Australia 800 kilometers north of Perth, groups of up to 14 male dolphins form lifelong alliances. Together, subsets of three keep close tabs on potential female mates, swimming, turning, and surfacing in unison to guard and herd them—one female at a time. Scientists watching this behavior noticed these males often emit a unique “popping” call, making series of two to 49 very short sounds, 10 per second, over and over. e dolphins popping The scientists dragged four underwater microphones behind a motorboat and recorded 172 instances in which multiple males were “popping” together (above). When the males pop alone, their timing and tempo varies. But when they pop together, they do it at the same time and at the same rate, suggesting they are using the sounds to enhance their cooperation, the team reports today in the Proceedings of the Royal Society B. This synchronized popping may be a threat, as it tends to make the female dolphin move closer to her male guards. But more importantly, the researchers say, it may help reinforce that the males need to act—and talk—as one to ensure they get their gal. © 2020 American Association for the Advancement of Science

Keyword: Sexual Behavior; Aggression
Link ID: 27156 - Posted: 04.01.2020

By Matt McGrath Environment correspondent A new study that looks at lifespan in wild mammals shows that females live substantially longer than males. The research finds that, on average, females live 18.6% longer than males from the same species. This is much larger than the well-studied difference between men and women, which is around 8%. The scientists say the differences in these other mammals are due to a combination of sex-specific traits and local environmental factors. In every human population, women live longer than men, so much so that nine out of 10 people who live to be 110 years old are female. This pattern, researchers say, has been consistent since the first accurate birth records became available in the 18th Century. While the same assumption has been held about animal species, large-scale data on mammals in the wild has been lacking, Now, an international team of researchers has examined age-specific mortality estimates for a widely diverse group of 101 species. In 60% of the analysed populations, the scientists found that females outlived the males - on average, they had a lifespan that's 18.6% longer than males. "The magnitude of lifespan and ageing across species is probably an interaction between environmental conditions and sex-specific genetic variations," said lead author Dr Jean-Francois Lemaître, from the University of Lyon, France. He gives the example of bighorn sheep for which the researchers had access to good data on different populations. Where natural resources were consistently available there was little difference in lifespan. However, in one location where winters were particularly severe, the males lived much shorter lives. © 2020 BBC.

Keyword: Sexual Behavior; Evolution
Link ID: 27137 - Posted: 03.24.2020

By Inés Gutiérrez, Rodrigo Pérez Ortega Earlier this month, Mexico’s leading university, the National Autonomous University of Mexico (UNAM), announced that renowned neuroscientist Ranulfo Romo Trujillo would leave his position after being disciplined for an unspecified offense. According to a 4 March press release from UNAM, Romo Trujillo voluntarily asked to be separated from his job at UNAM’s University City campus in Mexico City. Sources close to the case say he had been temporarily suspended because a female worker made a formal complaint of sexual harassment against him following an incident in January. But current and former UNAM students and staff say that reports of inappropriate behavior by Romo Trujillo had circulated for years before his departure. Romo Trujillo, who works at UNAM’s Institute of Cellular Physiology (IFC), did not respond to repeated requests for comment. He is arguably the most famous neuroscientist in Mexico, studying perception, working memory, and decision-making. He has more than 150 publications, including in top journals such as Science and Nature; is on the editorial board of Neuron and other journals; and is one of 11 Mexican members of the U.S. National Academy of Sciences. IFC physiologist Marcia Hiriart Urdanivia acknowledged in an email to Science that, while director of IFC from 2009 to 2017, she received multiple accounts of sexual harassment or inappropriate conduct by Romo Trujillo. Hiriart Urdanivia says she warned Romo Trujillo that “his career was endangered by such actions.” But the women involved did not choose to file official complaints, she says. As a result, “I had no authority to do anything else.” © 2020 American Association for the Advancement of Science.

Keyword: Sexual Behavior
Link ID: 27129 - Posted: 03.21.2020

By Perri Klass, M.D. When you talk about sibling issues, everyone takes it personally. Whether it’s birth order and the supposed advantages of being the oldest (or youngest, or middle), or the question of having (or being) the favorite child, people tend to respond immediately with their own sometimes very individual and emotional stories. What I want to talk about today are sibling sex ratios — having a sibling of the other sex versus growing up in all-boy or all-girl sibling configurations. The most evocative phrase I’ve seen for this is “family constellations,” which I like because it suggests that there are lots of interesting — and even beautiful — arrangements, but that differences are real. But let’s take one step further back: Are there actually parents, or parent pairs, who are more likely to conceive boys or girls? Does the five-daughter family (from “Pride and Prejudice” or “Fiddler on the Roof”) or the seven-son setup (“Seven Brides for Seven Brothers”) just reflect five (or seven) random rolls of the dice, or is there actually something going on from an evolutionary point of view? The evolutionary theory, which has been advanced to explain sex ratio, goes back to Darwin, but was fully formulated in 1930 by a British scientist named Ronald Fisher, who made the argument that if individuals vary in the sex ratio among their offspring (that is, some are more likely to produce more males or more females), the reproductive advantage in a population will always lie with the rarer sex, and thus the sex ratio will equilibrate toward 1:1. After all, Fisher argued, half of the genetic material of the next generation must come by way of those who tend to produce males, and half from those who tend to produce females. But are there such tendencies? I’ve heard people say that having boys “runs in the family,” or that their cousins are almost all girls, that’s the “family pattern.” But a very large study of 4.7 million births in Sweden published in February in the journal Proceedings of the Royal Society argues that there is no evidence of a genetic tendency toward one sex or the other, or a family tendency. © 2020 The New York Times Company

Keyword: Development of the Brain; Sexual Behavior
Link ID: 27108 - Posted: 03.10.2020

Nicola Davis From humans to black-tailed prairie dogs, female mammals often outlive males – but for birds, the reverse is true. Now researchers say they have cracked the mystery, revealing that having two copies of the same sex chromosome is associated with having a longer lifespan, suggesting the second copy offers a protective effect. “These findings are a crucial step in uncovering the underlying mechanisms affecting longevity, which could point to pathways for extending life,” the authors write. “We can only hope that more answers are found in our lifetime.” The idea that a second copy of the same sex chromosome is protective has been around for a while, supported by the observation that in mammals – where females have two of the same sex chromosomes – males tend to have shorter lifespans. In birds, males live longer on average and have two Z chromosomes, while females have one Z and one W chromosome. Scientists say they have found the trend is widespread. Writing in the journal Biology Letters, the team report that they gathered data on sex chromosomes and lifespan across 229 animal species, from insects to fish and mammals. Hermaphroditic species and those whose sex is influenced by environmental conditions – such as green turtles – were not included. The results reveal that individuals with two of the same sex chromosomes live 17.6% longer, on average, than those with either two different sex chromosomes or just one sex chromosome. The team say the findings back a theory known as the “unguarded X hypothesis”. In human cells, sex chromosome combinations are generally either XY (male) or XX (female). In females only one X chromosome is activated at random in each cell. © 2020 Guardian News & Media Limited

Keyword: Sexual Behavior; Evolution
Link ID: 27090 - Posted: 03.04.2020

Dominique Sisley Nothing is quite as shattering as a broken heart. A bad breakup has been known to trigger a range of psychological and physical symptoms, from nausea and insomnia to clinical depression. In more extreme scenarios, broken heart syndrome – when a person’s heart stops pumping blood properly after an emotional shock – can lead to death. Fortunately, recent breakthroughs suggest we may soon be able to beat it. In March, a Spanish study found propofol, a sedative used for anaesthesia, may also be able to mute the painful memories that come with heartbreak. Participants were injected with the drug immediately after recalling a distressing story and, when asked to recount it again 24 hours later, they found the memory to be less vivid. Advertisement The principal goal of the research was to relieve the symptoms of post-traumatic stress disorder (PTSD), but it seems there may be scope for the drug to be used to suppress other upsetting memories. An unexpected loss such as heartbreak can also be traumatic, and some people report similar symptoms. Dr Bryan Strange, who led the study, says: “Combining anaesthesia with evoking an emotionally charged memory impairs its subsequent recall. We will need to derive a set of criteria that identify people for whom it works well, and where the benefit justifies the risk of anaesthesia. There may well be those for whom heartbreak is so distressing that the criteria is fulfilled.” In the past year, a wave of apps such as Mend, Rx Breakup and Break-Up Boss have been released, promising guidance, advice and distracting activities to help soothe the pain of heartbreak. It is a lofty promise, but one that appears to be rooted in logic: a study in 2017 found similar brain-training style exercises could help curb embarrassing or impulsive post-breakup behaviour and strengthen self-control. © 2020 Guardian News & Media Limited

Keyword: Depression; Sexual Behavior
Link ID: 27066 - Posted: 02.24.2020

By Shola Lawal These are tough times for fireflies. Like a lot of other insects, they face increasing threats from habitat loss, pesticides and pollution. But they also have a problem that’s unique to luminous bugs: It’s getting harder for them to reproduce because light pollution is outshining their mating signals. Fireflies, it turns out, use their special glowing powers in courtship: Males light up to signal availability and females respond with patterned flashes to show that they’re in the mood. But bright light from billboards, streetlights and houses is interfering and blocking potential firefly couples from pairing up. The problem can reach far from big cities: Bright light gets diffused in the atmosphere and can be reflected into the wilderness. In addition to messing with mating signals, it also disrupts the feeding patterns of the females of some species that glow to attract and eat males. The finding was part of a study published Monday in the journal BioScience. The study, by researchers at Tufts University and the International Union for Conservation of Nature, warned that fireflies could eventually face extinction globally because of multiple threats, including light pollution and habitat loss and habitat degradation from insecticides and chemical pollution. Many insects are affected by habitat loss, but fireflies have it particularly bad, said Sara M. Lewis, a biology professor at Tufts and the lead researcher on the study. “Some fireflies get hit especially hard when their habitat disappears because they need special conditions to complete their life cycle,” she said. Fireflies are a type of beetle. There are more than 2,000 species of them, found mainly in wetlands. But mangrove forests and marshes around the world are increasingly vanishing to make way for cash crops like palm oil, according to the new study. © 2020 The New York Times Company

Keyword: Sexual Behavior; Biological Rhythms
Link ID: 27018 - Posted: 02.04.2020