By Rachel E. Gross Estrogen is the Meryl Streep of hormones, its versatility renowned among scientists. Besides playing a key role in sexual and reproductive health, it strengthens bones, keeps skin supple, regulates sugar levels, increases blood flow, lowers inflammation and supports the central nervous system. “You name the organ, and it promotes the health of that organ,” said Roberta Brinton, a neuroscientist who leads the Center for Innovation in Brain Science at the University of Arizona. But appreciation for estrogen’s more expansive role has been slow in coming. The compound was first identified in 1923 and was henceforth known as the “female sex hormone” — a one-dimensional reputation baked into its very name. “Estrogen” comes from the Greek “oestrus,” a literal gadfly known for whipping cattle into a mad frenzy. Scientifically, estrus has come to mean the period in the reproductive cycles of some mammals when females are fertile and sexually active. Women don’t enter estrus; they menstruate. Nevertheless, when researchers named estrogen, these were the roles it was cast in: inducing a frenzy and supporting female sexual health. Now, estrogen is gaining recognition for what may be its most important role yet: influencing the brain. Neuroscientists have learned that estrogen is vital to healthy brain development but that it also contributes to conditions including multiple sclerosis and Alzheimer’s. Changes in estrogen levels — either from the menstrual cycle or external sources — can exacerbate migraines, seizures and other common neurological symptoms. “There are a huge number of neurological diseases that can be affected by sex hormone fluctuations,” said Dr. Hyman Schipper, a neurologist at McGill University who listed a dozen of them in a recent review in the journal Brain Medicine. “And many of the therapies that are used in reproductive medicine should be repurposed for these neurological diseases.” Today, the insight that sex hormones are also brain hormones is transforming how doctors approach brain health and disease — helping them guide treatment, avoid harmful interactions and develop new hormone-based therapies.. © 2025 The New York Times Company

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 29757 - Posted: 04.23.2025

is a psychologist, writer and professor in the history and philosophy of science programme at the University of Melbourne. She is the author of Delusions of Gender: How Our Minds, Society, and Neurosexism Create Difference (2010), Testosterone Rex: Myths of Sex, Science, and Society (2017) and Patriarchy Inc.: What We Get Wrong About Gender Equality – and Why Men Still Win at Work (2025). She lives in Melbourne, Australia. Carole Hooven is a human evolutionary biologist with a focus on behavioural endocrinology. She is a nonresident senior fellow at the American Enterprise Institute, an associate in Harvard’s Department of Psychology, and the author of T: The Story of Testosterone, the Hormone That Dominates and Divides Us (2021). She lives in Cambridge, Massachusetts. Does biology determine destiny, or is society the dominant cause of masculine and feminine traits? In this spirited exchange, the psychologist Cordelia Fine and the evolutionary biologist Carole Hooven unpack the complex relationship between testosterone and human behaviour. Fine emphasises variability, flexibility and context – seeing gender as shaped by social forces as much as it is by hormones. By contrast, Hooven stresses consistent patterns; while acknowledging the influence of culture and the differences between individuals, she maintains that biology explains why certain sex-linked behaviours persist across cultures. © Aeon Media Group Ltd. 2012-2025.

Keyword: Sexual Behavior; Evolution
Link ID: 29733 - Posted: 04.09.2025

By Nathan H. Lents For generations, anthropologists have argued whether humans are evolved for monogamy or some other mating system, such as polygyny, polyandry, or promiscuity. But any exploration of monogamy must begin with a bifurcation of the concept into two completely different phenomena: social monogamy and sexual monogamy. WHAT I LEFT OUT is a recurring feature in which book authors are invited to share anecdotes and narratives that, for whatever reason, did not make it into their final manuscripts. In this installment, author Nathan H. Lents, professor of biology at John Jay College, shares a story that didn’t make it into his recent book “The Sexual Evolution: How 500 Million Years of Sex, Gender, and Mating Shape Modern Relationships” (Mariner Books). Sexual monogamy is just what it sounds like: The restriction of sexual intercourse to within a bonded pair. Social monogamy, also known as economic monogamy, describes the bonding itself, a strong, neurohormone-driven attachment between two adults that facilitates food and territory sharing, to the exclusion of others, for at least one breeding season, and generally purposed towards raising offspring. Because these two aspects of monogamy are so often enjoined among humans, they are considered two sides of the same coin. But, as it turns out, they are entirely separable among animals. In fact, social monogamy is extremely common in birds and somewhat common in mammals, while sexual monogamy is vanishingly rare among any species. Because of the unique way their embryos develop — externally but with constant warmth required — birds are the real stars of monogamy and have thus borne the brunt of its misconceptions. The marriage (if you’ll pardon the pun) of two very different behaviors into one concept is — and always was — unsupported by evidence from the natural world. Monogamy, as it is commonly understood, was the invention of anthropomorphic bias. Naturalists in the 19th and 20th centuries documented how pairs of various bird species dutifully toiled together building a nest, protecting the eggs, mutually feeding each other and their offspring, before eventually flying off into the sunset together. These prim and proper Victorians didn’t have to squint very hard to see a perfect model in nature of what they valued most in human society — lifelong and sexually exclusive marriage.

Keyword: Sexual Behavior; Evolution
Link ID: 29728 - Posted: 04.05.2025

By Gina Kolata Women’s brains are superior to men’s in at least in one respect — they age more slowly. And now, a group of researchers reports that they have found a gene in mice that rejuvenates female brains. Humans have the same gene. The discovery suggests a possible way to help both women and men avoid cognitive declines in advanced age. The study was published Wednesday in the journal Science Advances. The journal also published two other studies on women’s brains, one on the effect of hormone therapy on the brain and another on how age at the onset of menopause shapes the risk of getting Alzheimer’s disease. The evidence that women’s brains age more slowly than men’s seemed compelling. Researchers, looking at the way the brain uses blood sugar, had already found that the brains of aging women are years younger, in metabolic terms, than the brains of aging men. Other scientists, examining markings on DNA, found that female brains are a year or so younger than male brains. And careful cognitive studies of healthy older people found that women had better memories and cognitive function than men of the same age. Dr. Dena Dubal, a professor of neurology at the University of California, San Francisco, set out to understand why. “We really wanted to know what could underlie this female resilience,” Dr. Dubal said. So she and her colleagues focused on the one factor that differentiates females and males: the X chromosome. Females have two X chromosomes; males have one X and one Y chromosome. Early in pregnancy, one of the X chromosomes in females shuts down and its genes go nearly silent. But that silencing changes in aging, Dr. Dubal found. © 2025 The New York Times Company

Keyword: Alzheimers; Sexual Behavior
Link ID: 29704 - Posted: 03.12.2025

By Pam Belluck Postpartum depression affects about one in every seven women who give birth, but little is known about what happens in the brains of pregnant women who experience it. A new study begins to shed some light. Researchers scanned the brains of dozens of women in the weeks before and after childbirth and found that two brain areas involved in the processing and control of emotions increased in size in women who developed symptoms of postpartum depression. The results, published Wednesday in the journal Science Advances, constitute some of the first evidence that postpartum depression is associated with changes in the brain during pregnancy. Researchers found that women with symptoms of depression in the first month after giving birth also had increases in the volume of their amygdala, a brain area that plays a key role in emotional processing. Women who rated their childbirth experience as difficult or stressful — a perception that is often associated with postpartum depression — also showed increases in the volume of the hippocampus, a brain area that helps regulate emotions. “This is really the first step in trying to understand how does the brain change in people who have a normal course of pregnancy and then those who experience perinatal depression, and what can we do about it,” said Dr. Sheila Shanmugan, an assistant professor of psychiatry, obstetrics-gynecology and radiology at the University of Pennsylvania who was not involved in the study. “The big takeaways are about how there are these really profound brain changes during pregnancy and how now we’re seeing it in depression circuitry specifically,” she said. The study was conducted in Madrid by a team that has led efforts to document the effects of pregnancy on the brain. It is part of a growing body of research that has found that certain brain networks, especially those involved in social and emotional processing, shrink during pregnancy, possibly undergoing a fine-tuning process in preparation for parenting. Such changes correspond with surges in pregnancy hormones, especially estrogen, and some last at least two years after childbirth, researchers have found. © 2025 The New York Times Company

Keyword: Hormones & Behavior; Depression
Link ID: 29699 - Posted: 03.08.2025

By Katherine Bourzac Women tend to live longer than men and are often more resilient to cognitive decline as they age. Now researchers might have uncovered a source for this resilience: the second X chromosome in female cells that was previously considered ‘silent’. In work published today in the journal Science Advances1, a team reports that, at least in female mice, ageing activates expression of genes on what is usually the ‘silent’, or inactivated, X chromosome in cells in the hippocampus, a brain region crucial to learning and memory. And when the researchers gave mature mice of both sexes a type of gene therapy to boost expression of one of those genes, it improved their cognition, as measured by how well they explored a maze. Assuming these results can be confirmed in humans, the team suggests it could mean that women’s brains are being protected by their second X chromosome as they age — and that the finding could translate into future therapies boosting cognition for everyone. “The X chromosome is powerful,” says Rachel Buckley, a neurologist who studies sex differences in Alzheimer’s disease at Massachusetts General Hospital in Charlestown, and who was not involved in the research. This kind of work, she says, is helping researchers to understand “where female resilience lies and how to harness it”. (This article uses ‘women’ and ‘female’ to describe people with two X chromosomes and no Y chromosome, reflecting the language of the study. Nature recognizes that not all people who identify as women have this chromosomal make-up.) Double dose Female cells typically have two X chromosomes, one from each parent; male cells usually have one X and one Y. Early in development, one of the two X chromosomes in female cells is inactivated — coated in various proteins and RNA molecules that prevent its genes from being expressed. Which one is ‘silenced’ — meaning which parent it comes from — is random, and the tissues in the body are a mosaic of both types. © 2025 Springer Nature Limited

Keyword: Sexual Behavior; Stress
Link ID: 29698 - Posted: 03.08.2025

By Donna L. Maney It’s springtime in your backyard. You watch a pair of little brown songbirds flit about, their white throats flashing in the sun. One of the birds has striking black and white stripes on its crown and occasionally belts out its song, “Old Sam Peabody, Peabody, Peabody.” Its partner is more drab, with tan and gray stripes on its head and brown streaks through its white throat. Knowing the conventional wisdom about songbirds—that the males are flashy show-offs and the females more camouflaged and quiet—you decide to name the singer with bright plumage Romeo and the subtler one Juliet. But later that day you notice Juliet teed up on the fence, belting out a song. Juliet’s song is even louder and showier than Romeo’s. You wonder, Do female birds sing? Then you see Romeo bringing a twig to the pair’s nest, hidden under a shrub. Your field guide says that in this species the female builds the nest by herself. What is going on? Turns out, when you named Romeo and Juliet, you made the same mistake 19th-century artist and naturalist John Audubon did when, in his watercolor of this species, he labeled the bright member of the pair “male” and the drab one “female.” Romeo might look male, even to a bird expert such as Audubon, but will build a nest and lay eggs in it. Juliet, who might look female, has testes and will defend the pair’s territory by singing both alone and alongside Romeo, who also sings. Juliet and Romeo are White-throated Sparrows (Zonotrichia albicollis). At first glance, members of this species of songbird might look rather ordinary. For example, like many other songbirds, one member of each breeding pair of these sparrows has more striking plumage—that is, its appearance is what we would traditionally consider malelike for songbirds. The other bird in the pair is more femalelike, with drabber plumage. © 2024 SCIENTIFIC AMERICAN

Keyword: Sexual Behavior; Evolution
Link ID: 29686 - Posted: 02.26.2025

By Jason Bittel Elaborate poses, tufts of feathers, flamboyant shuffles along an immaculate forest floor — male birds-of-paradise have many ways to woo a potential mate. But now, by examining prepared specimens at the American Museum of Natural History in New York, scientists have discovered what could be yet another tool in the kit of the tropical birds — a visual effect known as photoluminescence. Sometimes called biofluorescence in living things, this phenomenon occurs when an object absorbs high-energy wavelengths of light and re-emits them as lower energy wavelengths. Biofluorescence has already been found in various species of fishes, amphibians and even mammals, from bats to wombats. Interestingly, birds remain woefully understudied when it comes to the optical extras. Until now, no one had looked for the glowing property in birds-of-paradise, which are native to Australia, Indonesia and New Guinea and are famous for their elaborate mating displays. In a study published on Tuesday in the journal Royal Society Open Science, researchers examined prepared specimens housed at the American Museum of Natural History and found evidence of biofluorescence in 37 of 45 birds-of-paradise species. “What they’re doing is taking this UV color, which they can’t see, and re-emitting it at a wavelength that is actually visible to their eyes,” said Rene Martin, the lead author of the study and a biologist at the University of Nebraska-Lincoln. “In their case, it’s kind of a bright green and green-yellow color.” In short, biofluorescence supercharges a bright color to make it even brighter. © 2025 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 29666 - Posted: 02.12.2025

By Marija Kundakovic The role of sex and gender in the brain is a popular but controversial research topic. Neuroscience has a reputation for being male-centric and focused on studying male brains, although researchers have recently embraced the idea that it is critical to study female brains as well. Generally speaking, human female and male brains are morphologically similar, but that does not suggest they don’t differ in their activity and function, or in their underlying molecular and cellular mechanisms. In fact, sex and gender bias in neuropsychiatric conditions is the rule rather than the exception. Men are three to five times as likely as women to have autism or attention-deficit/hyperactivity disorder, for example, and women are twice as likely as men to have anxiety or depression disorders. Understanding the biological factors and mechanisms that underlie gender- and sex-related bias in brain function and psychiatric conditions is essential to improve our fundamental knowledge of the brain and to open a path to develop novel, sex-informed treatments. But simply including females in research studies is insufficient to resolve the role of sex and gender in neuroscience. “Sex” and “gender” are both complex and evolving concepts, extending beyond a simple binary. In practice, people are assigned female or male at birth based on external genitalia, although up to 2 percent do not belong to either category because of differences in sex development. Though gender has traditionally been co-assigned with sex—females/women and males/men—the binary nature of sex does not suffice to account for today’s expanding gender landscape. Gender exists on a spectrum, including nonbinary, gender-fluid and agender people. In transgender people, gender identity differs from gender or sex assigned at birth. Some researchers would say that this complexity cannot (and perhaps should not) be tackled by science, and that we should stick to scientifically discernible female-male comparisons, particularly in animal research. But science should not exist in a vacuum; when detached from society, it does not serve its purpose. Indeed, in the case of gender, biology can be falsely used to fuel discriminatory laws and practices against gender-diverse and gender-non-conforming people, supposedly based on a scientific understanding of “biological sex.” © 2025 Simons Foundation

Keyword: Sexual Behavior
Link ID: 29651 - Posted: 02.01.2025

By Holly Barker Previously unrecognized genetic changes on the X chromosome of autistic people could explain the higher prevalence of the condition among men and boys than among women and girls, according to two new studies. About 60 variants are more common in people with autism than in those without the condition, an analysis of roughly 15,000 X chromosomes revealed. Several of the variants are in Xp22.11, a region of the X chromosome linked to autism in boys and men. In the second study, the team pinpointed 27 autism-linked variants in DDX53, one of the genes in the vulnerable region that had not been tied to the condition in past research. Those findings could help explain why autism is diagnosed three to four times more often in boys than girls, according to the study investigators, led by Stephen Scherer, chief of research at SickKids Research Institute. Although that disparity is likely influenced by social factors—male-only studies could lead to autism being less recognizable in women and girls, and girls may be conditioned to mask their autism traits—there is also a clear biological component. The X chromosome plays an outsized role in brain development, and many genes on the chromosome are strongly linked to autism, previous studies have found. Still, the sex chromosomes have been mostly ignored in genetic searches of autism variants, says Aaron Besterman, associate clinical professor of psychiatry at the University of California, San Diego, who was not involved in the work. “It’s been a dirty little secret that for a long time the X chromosome has not been well interrogated from a genetics perspective,” he says. Sex chromosomes are often sidelined because of difficulties interpreting data, given that men possess half the number of X-linked genes as women. What’s more, random inactivation of X chromosomes makes it hard to tell how a single variant is expressed in female tissues. And the existence of pseudoautosomal regions—stretches of DNA that behave like regular chromosomes and escape inactivation—complicates matters further. © 2025 Simons Foundation

Keyword: Autism; Sexual Behavior
Link ID: 29638 - Posted: 01.22.2025

By Shaena Montanari Just as romantic partners exhibit more similar brain waves than do strangers when, say, drawing on an Etch A Sketch toy together, animal pairs also show neural synchrony during social interactions and cooperation tasks. “Neural synchrony is something that happens in these minute-to-minute engagements that you have with another individual,” says Zoe Donaldson, associate professor of behavioral neuroscience at the University of Colorado Boulder. But over time, too, pairs in a relationship learn to infer what their partner is going to do, she adds. In prairie voles, at least, that learning process may unfold at the molecular level in the form of “transcriptional synchrony,” according to a preprint Donaldson and her colleagues posted on bioRxiv in November. Prairie voles are socially monogamous, and after two of them bond, gene-expression patterns in their nucleus accumbens—a forebrain region linked to reward and social interaction—start to align. It remains unclear whether this transcriptional synchrony causes pair bonding or only correlates with it, she adds, but in the meantime, it offers researchers a new place to hunt for the basis of these strong social ties. This new study “pushes the limits of what’s possible” technically, says Robert Froemke, professor in New York University’s Neuroscience Institute and otolaryngology department, who was not involved in the study. Though the existence of neural synchrony logically suggests that there may also be shared patterns of gene expression, “it’s still remarkable to actually have it documented,” he says. The new preprint offers the first evidence of transcriptional synchrony in prairie voles, Donaldson says, but a 2020 study revealed that fighting pairs of Betta splendens fish show a strong correlation of gene expression after 60 minutes of fighting, and only a weak correlation after 20 minutes. © 2025 Simons Foundation

Keyword: Sexual Behavior
Link ID: 29630 - Posted: 01.15.2025

By Emily McLaughlin Three days after our baby was born, my husband and I brought our newborn daughter home to our house in Tarrytown, New York. I was 32, fit and healthy, and had had an uneventful pregnancy. But on the second afternoon back home, while nursing, a thunderclap headache struck. The pounding in my temple literally brought me to my knees. I tried to tough it out, but it didn’t go away. That evening, I called my doctor. Since I was low-risk with normal blood pressure, she suggested rest and hydration. Then in the middle of that night, while I was still in debilitating pain, dark spots started to float across my vision. As my husband rushed me to the hospital, he asked me a few simple questions as he drove: Did you page the doctor? How’s your nausea? My answers came out in slow motion at first, then turned into a stutter, before they finally stopped. At the hospital, an emergency brain scan showed an intracerebral hemorrhage in the right frontal lobe — the site of executive functioning, creativity and emotion. The next thing I remember is waking in the Neuro-ICU of a nearby hospital — paralyzed on the left side, unable to smile, process time or even read the sign telling nurses I wasn’t allowed to swallow in case the muscles in my mouth were affected and I choked. I couldn’t get the words out to ask if I’d be trapped in my head for good. Ten days later, on blood pressure and antiseizure meds, I was finally allowed to go home to my newborn. It felt like I needed more care than she did. With only one strong, normally working arm, I couldn’t cradle my baby. A constant headache made it impossible to stand. Doctors said the headaches might last a year, until the blood in my brain reabsorbed. My left leg worked, but poor balance made even walking around the house difficult. The left half of my face couldn’t move, and my speech came out weak and slowly. I could not connect emotion to the rhythm of my words. I delivered questions as flat, imperative statements.

Keyword: Stroke; Hormones & Behavior
Link ID: 29604 - Posted: 12.21.2024

By Grace Huckins Genes on the X and Y chromosomes—and especially those on the Y—appear to be associated with autism likelihood, according to a study focused on people who have missing or extra sex chromosomes. The findings add to the ongoing debate about whether autism’s sex bias reflects a male vulnerability, a female protective effect or other factors. “The Y chromosome is often left out of genetic discovery studies. We really have not interrogated it in [autism] studies very much,” says Matthew Oetjens, assistant professor of human genetics at Geisinger Medical Center’s Autism and Developmental Medicine Institute, who led the new work. There is a clear sex difference in autism prevalence: Men are about four times as likely as women to have a diagnosis. But uncovering the reasons for that discrepancy has proved challenging and contentious. Multiple biological factors may play a role, in addition to social factors—such as the difficult-to-measure gulfs between how boys and girls are taught to behave. Add on the possibility of diagnostic bias and the question starts to look less like a scientific problem and more like a politically toxic Gordian knot. But there are some threads that researchers can pull to disentangle these effects, as the new study illustrates. People with sex chromosome aneuploidies—or unusual combinations of sex chromosomes, such as XXY in those with Klinefelter syndrome or a single X in Turner syndrome—provide a unique opportunity to examine how adding or taking away chromosomes can affect biology and behavior. Previous studies noted high rates of autism in people with sex chromosome aneuploidies, but those analyses were subject to ascertainment bias; perhaps those people found out about their aneuploidies only after seeking support for their neurodevelopmental conditions. © 2024 Simons Foundation

Keyword: Autism; Sexual Behavior
Link ID: 29596 - Posted: 12.11.2024

By Tim Vernimmen Few people are fond of earwigs, with their menacing abdominal pincers — whether they’re skittering across your floor, getting comfy in the folds of your camping tent or minding their own business. Scientists, too, have given them short shrift, compared with the seemingly endless attention they have lavished on social insects like ants and bees. Yet there are a handful of exceptions. Some researchers have made conscious career decisions to dig into the hidden, underground world where earwigs reside, and have found the creatures to be surprisingly interesting and social, if still not exactly endearing. Work in the 1990s and early 2000s focused on earwig courtship. These often-intricate performances of attraction and repulsion — in which pincers and antennae play prominent roles — can last hours, and the mating itself as long as 20 hours, at least in one Papua New Guinea species, Tagalina papua. The females usually decide when they’ve had enough, though males of some species use their pincers to restrain the object of their desire. Males of the bone-house earwig Marava arachidis (often found in bone meal plants and slaughterhouses) are particularly coercive, says entomologist Yoshitaka Kamimura of Keio University in Japan, who has studied earwig mating for 25 years. “They bite the female’s antennae and use a little hook on their genitalia to lock them inside her reproductive tract.” Size matters

Keyword: Sexual Behavior; Evolution
Link ID: 29559 - Posted: 11.16.2024

Andrew Gregory Health editor Doing more than an hour of moderate intensity exercise each week may reduce the severity of “baby blues” and almost halve the risk of new mothers developing major clinical depression, the largest analysis of evidence suggests. However, researchers behind the study acknowledged that finding the time amid so many new responsibilities and challenges would not be easy, and recovery from childbirth should be prioritised. New mothers could restart exercise with “gentle” walks, which they could do with their babies, and then increase to “moderate” activity when they were ready, they added. This moderate physical activity could include brisk walking, water aerobics, stationary cycling or resistance training, according to the team of academics in Canada. Maternal depression and anxiety are relatively common after giving birth and associated with reduced self-care and compromised infant caregiving and bonding, which could in turn affect the child’s cognitive, emotional and social development, the researchers said. Conventional treatments for depression and anxiety in the first weeks and months after giving birth mostly involve drugs and counselling, which are often associated with, respectively, side-effects and poor adherence, and lack of timely access and expense. Research has previously shown that physical activity is an effective treatment for depression and anxiety in general. But until now it has not been known whether it could reduce the severity of the baby blues in the first few weeks after giving birth or lower the risk of major postpartum depression several months later. © 2024 Guardian News & Media Limited

Keyword: Depression; Hormones & Behavior
Link ID: 29548 - Posted: 11.09.2024

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

Keyword: Sexual Behavior; Evolution
Link ID: 29532 - Posted: 10.30.2024

By Claudia López Lloreda Success tends to breed success. For instance, when a mouse dominates its opponents over and over, it becomes increasingly aggressive—helping to ensure victory in future fights. This “winner effect” takes hold thanks to multiple changes in synaptic plasticity, according to new findings published today in Cell. The results begin to reveal the mechanisms behind various forms of aggression seen in animals, says Jacob Nordman, assistant professor of molecular and integrative physiology at Southern Illinois University, who was not involved in the work. “There’s some aggression that is defensive; there’s some aggression that is pathological; there’s some aggression that’s territorial,” he says. “There might be a set of behaviors and, in turn, a set of circuits and possibly plasticity within those circuits, that speak to that.” Innate aggression is controlled by the ventromedial hypothalamus (VMH)—also known as the “attack” center—which shapes an animal’s social behaviors and fear response. But aggression can be learned, too. When paired with a mouse that is naturally docile, a more dominant mouse will eventually attack the other—and if it prevails, it tends to pick even longer fights with rivals over the coming days, thanks to synapse strengthening and increased activity in the VMH, a 2020 study reported. Full-blown and more generalized aggression emerges after even longer winning streaks, and it involves additional mechanisms, the new study suggests: Changes to neuronal excitability and dendritic spine morphology help cement the animal’s hawkishness. “Aggression is malleable—you can shape it,” says Scott Russo, professor of neuroscience at the Icahn School of Medicine at Mount Sinai, who was not involved with the study. “It’s not something that’s defined only by genetics, but that actually these circuits that support aggressive social behavior can change as a consequence of experience.” © 2024 Simons Foundation

Keyword: Aggression; Hormones & Behavior
Link ID: 29524 - Posted: 10.19.2024

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

Keyword: Sexual Behavior; Evolution
Link ID: 29505 - Posted: 10.05.2024

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

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 29485 - Posted: 09.18.2024

By Ellen Barry A study of adolescent brain development that tested children before and after coronavirus pandemic lockdowns in the United States found that girls’ brains aged far faster than expected, something the researchers attributed to social isolation. The study from the University of Washington, published on Monday in the Proceedings of the National Academy of Sciences, measured cortical thinning, a process that starts in either late childhood or early adolescence, as the brain begins to prune redundant synapses and shrink its outer layer. Thinning of the cortex is not necessarily bad; some scientists frame the process as the brain rewiring itself as it matures, increasing its efficiency. But the process is known to accelerate in stressful conditions, and accelerated thinning is correlated with depression and anxiety. Scans taken in 2021, after shutdowns started to lift, showed that both boys and girls had experienced rapid cortical thinning during that period. But the effect was far more notable in girls, whose thinning had accelerated, on average, by 4.2 years ahead of what was expected; the thinning in boys’ brains had accelerated 1.4 years ahead of what was expected. “That is a stunning difference,” said Patricia K. Kuhl, a director of the Institute for Learning and Brain Sciences at the University of Washington and one of the study’s authors. The results, she added, suggested that “a girl who came in at 11, and then returned to the lab at age 14, now has a brain that looks like an 18-year-old’s.” Dr. Kuhl attributed the change to “social deprivation caused by the pandemic,” which she suggested had hit adolescent girls harder because they are more dependent on social interaction — in particular, talking through problems with friends — as a way to release stress. The difference between the genders “is just as clear as night and day,” Dr. Kuhl said. “In the girls, the effects were all over the brain — all the lobes, both hemispheres.” © 2024 The New York Times Company

Keyword: Stress; Development of the Brain
Link ID: 29477 - Posted: 09.11.2024