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

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By Emily Oster In 1980, 8.6 percent of first births were to women over 30; by 2015 this was 31 percent. This is more than an interesting demographic fact. It means that many of us are having children much later than our parents did. By the time a baby arrives, many of us have been through school, spent time in the working world, developed friendships, hobbies. And through all of these activities, we have probably grown used to the idea that if we work harder — at our jobs, at school, at banking that personal record in the half marathon — we can achieve more. Babies, however, often do not respond to a diligent work ethic. Take, as an example, crying. When my daughter, Penelope, was an infant, she was typically inconsolable between 5 and 8 p.m. I’d walk her up and down the hall, sometimes just crying (me crying, that is — obviously she was crying). I once did this in a hotel — up and down, up and down, Penelope screaming at the top of her lungs. I hope no one else was staying there. I tried everything — bouncing her more, bouncing her less, bouncing with swinging, bouncing with nursing (difficult). Nothing worked; she would eventually just exhaust herself. I wondered whether this was normal. I’m an economist, someone who works with data. I wrote a book on using data to make better choices during pregnancy; it was natural for me to turn to the data again once the baby arrived. And here, faced with crying, I found that the data was helpful. We often say babies are “colicky,” but researchers have an actual definition of colic (three hours of crying, more than three days a week, for more than three weeks) and some estimates of what share of babies fit this description (about 2 percent). But the same data can also tell us that many babies cry just a bit less than that, and almost 20 percent of parents report their baby “cries a lot.” So I was not alone. The data also told me the crying would get better, which it eventually did. © 2019 The New York Times Company

Keyword: Sexual Behavior
Link ID: 26162 - Posted: 04.22.2019

Nicola Davis Philandering men have unfaithfulness written all over their faces, according to research that suggests men and women are able to spot cheating chaps just by looking at them. Experts found men with more “masculine” faces were more likely to be thought to be unfaithful, and such men also self-reported more cheating or “poaching” of other men’s partners. However, they stressed the results were modest, and said people should be wary of deciding whether someone is a love rat based on impressions of facial features alone. The team said being suspicious of men with masculine features – such as a strong browridge, strong jaw and thinner lips – might have offered an evolutionary advantage, allowing heterosexual women to spot a flaky partner and men to recognise a potential rival who might seduce their partner or leave them raising someone else’s child. Previous research has suggested women are able to spot unfaithful men from their mugshot, with the masculinity of the man’s face a key factor in the judgment, while weaker effects have been found for men weighing up images of women. However, it was unclear whether people could also spot a philanderer of the same sex. Writing in the journal Royal Society Open Science, researchers described how they asked heterosexual white participants to judge the facial features of 189 white adults who had been photographed and taken part in previous research. Overall, 293 men and 472 women rated pictures of women, while 299 men and 452 women judged images of men, rating on a scale of one to 10 how likely they thought each person was to be unfaithful. © 2019 Guardian News & Media Limited

Keyword: Sexual Behavior; Evolution
Link ID: 26147 - Posted: 04.17.2019

Robert J King Ph.D. Saying that people deserve to be treated decently is not a factual claim. You can’t look it up in a textbook, and no amount of brain-scanning is going to reveal why it’s true. People have been either succeeding (or more often failing) to treat each other kindly, fairly, and honorably, since before there was science, since before there were people really. And—they will continue to try (and often fail) far into the future, whatever science reveals about our natures. If I am trying to help a child understand why stealing from another child was wrong, or that they should share the sandpit, or apologize to that other annoying (and now crying) kid…yes…I know he took your dolly, but you still can’t hit him with that Lego dinosaur… Well, I don’t get out my copy of Eric Kandel's Principles of Neural Science, and start pointing meaningfully to the diagram of Brodmann area 11 in the prefrontal cortex. This seems blindingly obvious. However, the corollary: That you don’t need neurological backup to argue that you should treat people fairly, seems lost on writers like Cordelia Fine and Gina Rippon. Both are trying to argue that humans are neurological hermaphrodites, as if somehow admitting any sex differences in brains would mandate the unfair treatment of women. Gina Rippon is back to “debunk” neuroscience with her latest, The Gendered Brain: The New Neuroscience That Shatters The Myth Of The Female Brain. It is tempting to rebunk these debunkings but, if I am right in my guess about what is going on here, no amount of factual piling on is going to help. In fact—it may make things worse, because it’s going to convince writers like Fine and Rippon that some hideous conspiracy is occurring and, like some horrible feminist version of Alex Jones, that the whole of brain science is fake news. Let’s stop things before they get out of hand. © 2019 Sussex Publishers, LLC

Keyword: Sexual Behavior
Link ID: 26135 - Posted: 04.13.2019

Rhonda Voskuhl & Sabra Klein We are concerned that Lise Eliot’s review of Gina Rippon’s book The Gendered Brain (Nature 566, 453–454; 2019) undermines the premise that sex is a biological variable with respect to many medical conditions and drug responses (see J. A. Clayton and F. S. Collins Nature 509, 282–283; 2014). As president-elect and president, respectively, of the Organization for the Study of Sex Differences, we disagree with Eliot’s claim that the brain is “no more gendered than the liver or kidneys or heart”. We also disagree that sex differences in behaviour are due to cultural effects on newborns, not to biological effects. In our view, these are not mutually exclusive. Sex disparities occur in animal models that are not subject to cultural bias. The brain, like many organs, shows differences attributable to sex, both during health (see, for example, E. Luders et al. J. Neurosci. 29, 14265–14270; 2009) and during disease. Two-thirds of people with Alzheimer’s disease are women; twice as many men as women have Parkinson’s disease (see, for example, L. J. Young and D. W. Pfaff Front. Neuroendocrinol. 35, 253–254; 2014). And multiple sclerosis affects three times more women than men, although men with the condition develop neurological disability more quickly (see, for example, R. R. Voskuhl and S. M. Gold Nature Rev. Neurol. 8, 255–263; 2012). Sex is a modifier of disease risk and progression. © 2019 Springer Nature Publishing AG

Keyword: Sexual Behavior
Link ID: 26130 - Posted: 04.12.2019

By Sarah Mervosh He is called the “father of the American cavalry,” a Polish-born Revolutionary War hero who fought for American independence under George Washington and whose legend inspired the dedication of parades, schools, roads and bridges. But for more than 200 years, a mystery persisted about his final resting place. Historical accounts suggested the cavalryman, Casimir Pulaski, had been buried at sea, but others maintained he was buried in an unmarked grave in Savannah, Ga. Researchers believe they have found the answer — after coming to another significant discovery: The famed general was most likely intersex. New evidence suggests that although Pulaski identified and lived as a man, biologically, he did not fit into the binary definitions of male and female, a twist that helps explain why scientists could not previously identify his remains. The revelatory findings are detailed in a new documentary, “The General Was Female?,” which is showing on the Smithsonian Channel on Monday. The discovery offers historical representation to people who are intersex, a group that has often been stigmatized and overlooked throughout history. About one in 2,000 people is born with ambiguous genitalia, which can lead doctors to perform what advocates say are unnecessary and harmful surgeries, according to the Intersex Society of North America. But intersex includes a variety of conditions, and many more people have subtler variations in sex anatomy, which may manifest later in life — or not at all. Some estimates suggest that about 1.7 percent of the population has intersex traits, making such characteristics about as common as having red hair. Though Pulaski’s role in history has long been embraced in areas with strong Polish and Catholic ties — his birthday is an Illinois state holiday and he is celebrated with an annual Polish pride parade in New York City — the new findings now also place him alongside the few historical figures who are known to have had intersex traits. © 2019 The New York Times Company

Keyword: Sexual Behavior
Link ID: 26120 - Posted: 04.08.2019

Wency Leung A new Canadian study on how the birth control pill affects a woman’s ability to think is the latest to address a decades-old knowledge gap researchers say needs to be fixed: How oral contraceptives impact the brain. The study aims to test the working memory of around 60 young women who use oral contraceptives, says researcher Laura Gravelsins, a PhD student with the Einstein Lab on cognitive neuroscience, gender and health at the University of Toronto. Gravelsins is among a number of researchers exploring an area that has historically been overlooked. Since the introduction of the pill in the 1960s, hormonal contraceptives – which contain estrogen, progestin, or a combination of both – have become a preferred option for many women. Yet, due, in part, to past assumptions that the brain operates separately from the rest of body and a general lack of research into women’s health, scientists are only now investigating how they may influence mood and cognition. Another area that needs exploration is how sex hormones, including those naturally produced by the body, influence developing brains. At the University of British Columbia, researchers are currently recruiting 300 girls, ages 13 to 15, to study what role sex hormones may play in their emotional development. “We need more research,” says Dr. Gillian Einstein, a professor of psychology at University of Toronto and the Wilfred and Joyce Posluns Chair in Women’s Brain Health and Aging. “Women should demand more research on this.”

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 26110 - Posted: 04.03.2019

By Darby Saxbe Perinatal depression—depression that occurs during pregnancy or after the birth of a child—is surprisingly common, affecting about 1 in 7 women. And, although depression is debilitating at any time, it may carry a particularly heavy public health burden during the transition to parenthood. Women with depression are less likely to obtain medical care for themselves and their babies, and may struggle to bond with their infants. It’s no wonder that the children of depressed mothers experience heightened long-term risk of emotional and behavioral problems. Despite this grim picture, a new report from the US Preventive Services Task Force offers some hope. The USPSTF, a nonpartisan body of experts, reviews scientific research and makes recommendations for preventing disease. In the past, they’ve issued guidelines for lung cancer detection, aspirin use to prevent heart disease, and blood pressure screening. In a review recently published in the Journal of the American Medical Association (JAMA), the task force shared what they deemed “convincing evidence” that counseling (talk therapy) interventions can not just treat, but actually prevent, perinatal depression. This is exciting news given the high cost of depression during this time and the fact that, unlike other potential treatments for perinatal depression (like the new drug Zulresso), talk therapy is low-tech, relatively low-cost, and brings few side effects. In their report, the USPSTF reviewed 50 studies that they deemed to be at least “good or fair quality.” Almost all were randomized clinical trials, the gold standard for treatment research, in which a treatment is directly compared to a control group condition. About half of the studies focused on pregnant women, and the rest on postpartum women. Some studies targeted women who already had elevated risk for depression, based on risk factors like a personal or family history of depression, low socioeconomic status, and exposure to life stress or intimate partner violence. © 2019 Scientific American

Keyword: Depression; Hormones & Behavior
Link ID: 26109 - Posted: 04.03.2019

“What we didn’t know before was some individuals seem to be able to choose whether they lay eggs or give birth to live babies,” Whittington said on Wednesday. “That was pretty staggering. We had no idea that could be the case. So I think it just makes this lizard even weirder.” Previous research has shown that if a Sydney skink was taken north it would still lay eggs, while live bearers transferred south would also continue to reproduce as they previously did. “I’m curious to know what happens if you breed an egg layer with a live bearer – what do their sons and daughters do?” Whittington said. Another skink in South Australia has also been shown to be bimodal. Bougainville’s skinks give birth to babies on Kangaroo Island, while on the mainland they lay eggs. Only a handful of species in the world do this. The University of Sydney study into the three-toed skink will be published in Biology Letters this week. Whittington hopes to map where they lay eggs and where they give birth in further research. The three-toed skink, which looks like a baby snake with tiny legs, is widespread along Australia’s east coast and is often seen in gardens or compost heaps. © 2019 Guardian News & Media Limited

Keyword: Sexual Behavior
Link ID: 26106 - Posted: 04.03.2019

By Michael C. Reichert Early in my first go at being a father, I was hijacked by ancient impulses. Our family lived in a rowhouse neighborhood in Philadelphia, and right down the street was a small playground where gangs of boys gathered for games of stickball and basketball. My son loved playing sports. But he was unprepared for what developed as his friends grew older. After years together laughing and riding their tricycles and then bikes up and down the block, several of the boys grew angry and mean. Ultimately, they turned on my son, taunting him, leaving him out of their games. He began to trudge home, tail between his legs. And I felt called to action. At first, I tried to bolster his confidence so he would give the playground another go. But one Saturday morning I met him at the front steps and told him he could not come into the house. “You have to figure this out,” I said. “I’ll stay with you as long as you need, but I cannot let you just give up.” He tried to push past me, his humiliation becoming frantic. He melted down, screaming and crying. I kept saying: “You can do it. You don’t have to give up.” A neighbor poked her head out, concerned about what must have sounded like child abuse. Did I do the right thing? Even now I’m not sure. He did go back to the playground, and eventually managed some kind of truce with the other kids. He grew up into a fine man, a teacher, and understands I was trying to help, in my clumsy way. But while teaching him to stand up for himself, was I also passing along the prejudice that a boy should override his pain and never back down from a fight? What happened in my son’s peer group was perfectly predictable. Boyhood immerses boys in violence and the bullying that leads to it. High school boys are more likely than girls to have been in a physical fight in the past year and male children are more likely to have been victims of violence. Three types of male violence — violence against women, violence against other men and violence against themselves — are deeply interwoven. © 2019 The New York Times Company

Keyword: Sexual Behavior; Aggression
Link ID: 26098 - Posted: 04.01.2019

Amber Dance Robert Sorge was studying pain in mice in 2009, but he was the one who ended up with a headache. At McGill University in Montreal, Canada, Sorge was investigating how animals develop an extreme sensitivity to touch. To test for this response, Sorge poked the paws of mice using fine hairs, ones that wouldn’t ordinarily bother them. The males behaved as the scientific literature said they would: they yanked their paws back from even the finest of threads. But females remained stoic to Sorge’s gentle pokes and prods1. “It just didn’t work in the females,” recalls Sorge, now a behaviourist at the University of Alabama at Birmingham. “We couldn’t figure out why.” Sorge and his adviser at McGill University, pain researcher Jeffrey Mogil, would go on to determine that this kind of pain hypersensitivity results from remarkably different pathways in male and female mice, with distinct immune-cell types contributing to discomfort2. Sorge and Mogil would never have made their discovery if they had followed the conventions of most pain researchers. By including male and female mice, they were going against the crowd. At the time, many pain scientists worried that females’ hormone cycles would complicate results. Others stuck with males because, well, that’s how things were done. Today, inspired in part by Sorge and Mogil’s work and spurred on by funders, pain researchers are opening their eyes to the spectrum of responses across sexes. Results are starting to trickle out, and it’s clear that certain pain pathways vary considerably, with immune cells and hormones having key roles in differing responses. © 2019 Springer Nature Publishing AG

Keyword: Pain & Touch; Hormones & Behavior
Link ID: 26089 - Posted: 03.28.2019

By Gina Kolata Lucas was 5 before his parents, Bill and Marci Barton of Grand Haven, Mich., finally got an explanation for his difficulties standing up or climbing stairs. The diagnosis: muscular dystrophy. Mr. Barton turned to Google. “The first thing I read was, ‘no cure, in a wheelchair in their teens, pass in their 20s,” Mr. Barton said. “I stopped. I couldn’t read any more. I couldn’t handle it.” Then he found a reason to hope. For the first time ever, there are clinical trials — nearly two dozen — testing treatments that might actually stop the disease. The problem, as Mr. Barton soon discovered, is that the enrollment criteria are so restrictive that very few children qualify. As a result, families like the Bartons often are turned away. “There is so much hope, but it’s not for them,” said Kristin Stephenson, vice president of policy and advocacy at the Muscular Dystrophy Association in Chicago. Even for the parents whose lucky child qualifies, good news may be followed by agonizing, life-or-death choices. What treatments seem most promising? Should he be enrolled in a trial with a placebo arm? Should he be placed in a less risky study that aims to slow the progress of the disease but will not stop it? Should the parents take their chances with a trial now — or wait a year or two, as their child’s condition worsens, until something better comes along? Often there is no easy way to decide. “We talk to families every day,” said Debra Miller who founded the advocacy group, Cure Duchenne, after her son was diagnosed with the disease. “So many times they are looking at us and saying, ‘What do I do?’” © 2019 The New York Times Company

Keyword: Movement Disorders; Muscles
Link ID: 26076 - Posted: 03.25.2019

Laura Sanders With great fanfare, a new antidepressant entered the U.S. market in March, the first fundamentally new medicine for depression in decades. Based on the anesthetic ketamine, the drug — called Spravato — is intended to help people with severe depression quickly, taking effect within hours or days instead of the weeks that typical antidepressants take. But for all the hubbub, big questions have gone unanswered about the drug, developed by Janssen Pharmaceuticals, Inc. Some psychiatrists are concerned that the drug was approved by the U.S. Food and Drug Administration based on skimpy data, under standards that were less rigorous than those required for previous antidepressants. It remains unclear, for example, what happens as someone stops taking the drug, as well as whether it has long-term effects. The data on Spravato raise more questions than they answer, says psychiatrist Alan Schatzberg of Stanford University. “And I think that’s unfortunate.” Despite those unknowns, some psychiatrists are relieved to have another drug to try, particularly for people with depression so severe that other drugs have failed to help. Spravato “does something that very few things in psychiatry can do — it works for people who didn’t respond to other treatments, and it works fast,” says psychiatrist Dan Iosifescu of New York University’s School of Medicine. “I really welcome having another powerful tool in my toolbox.” |© Society for Science & the Public 2000 - 2019

Keyword: Depression; Hormones & Behavior
Link ID: 26065 - Posted: 03.23.2019

New rules to reduce naturally high testosterone levels in female athletes have been branded "unscientific". Last year, athletics chiefs ruled women with levels of five nanomoles per litre or more must have hormone treatment before being allowed to compete. But experts, reporting in the British Medical Journal, say there is a lack of evidence about testosterone's effects and the cut-off figure is arbitrary. A decision on the legality of the rules is expected later this month. The International Association of Athletics Federations (IAAF) delayed implementing its regulations after South African runner Caster Semenya contested the legality of the new rules. She was banned from international competitions for nearly a year for having testosterone levels above the athletics body's limit for female athletes. World athletics bosses have previously said they want to protect the sanctity of fair and open competition. Writing in an editorial in the BMJ, Dr Sheree Bekker, from the University of Bath, and Prof Cara Tannenbaum, from the University of Montreal, say the IAAF's regulations risked "setting an unscientific precedent for other cases of genetic advantage". "The medical profession does not define biological sex or physical function by serum testosterone levels alone," they say. And they warned that the proposed rules could have "far reaching implications" on individuals and societies. Dr Bekker and Prof Tannenbaum argue that testosterone levels vary naturally in men and women, with higher averages among elite athletes. But there is also a big crossover between men and women, with 16% of men classified as having low testosterone and 14% of women having high, according to some definitions. They say testosterone is just one indicator of sports performance and many other factors also play a role. "If more science is needed... then call for health research organisations to deliver on this mandate," they say. © 2019 BBC

Keyword: Sexual Behavior
Link ID: 26057 - Posted: 03.21.2019

By Pam Belluck The first drug for women suffering postpartum depression received federal approval on Tuesday, a move likely to pave the way for a wave of treatments to address a debilitating condition that is the most common complication of pregnancy. The drug works very quickly, within 48 hours — a significant improvement over currently available antidepressants, which can take two to four weeks to have an effect, if they work at all. Experts say the new treatment will provide immediate relief for mothers whose depression keeps them from providing their babies with the care, bonding and nurturing that is crucial for healthy development. As many as one in seven American women experience depression during or after pregnancy. "Postpartum depression is a serious condition that, when severe, can be life-threatening,” Dr. Tiffany Farchione, acting director of the Division of Psychiatry Products at the Food and Drug Administration’s Center for Drug Evaluation and Research, said in a statement. “This approval marks the first time a drug has been specifically approved to treat postpartum depression, providing an important new treatment option.” There are limitations to the new drug, brexanolone, which will be marketed as Zulresso. It is delivered by infusion over 60 hours, during which a new mother must remain in a certified medical center, under supervision should she get dizzy or faint, as several patients did in clinical trials. The infusion will be expensive, averaging $34,000 per patient before discounts, according to Sage Therapeutics, the manufacturer. That does not include the costs of staying in a medical center for two and half days. Company officials say they expect that insurers will cover the treatment; insurers said this week that they are evaluating the drug. A pill made with a similar molecule, which would be much more accessible and easier for patients, is showing promise in its clinical trials and would be submitted for approval in a couple of years if the results are good, according to Sage. © 2019 The New York Times Company

Keyword: Depression; Sexual Behavior
Link ID: 26055 - Posted: 03.20.2019

By Michael Price Female twins who shared a womb with a brother tend to get less education, earn less money, and have fewer children than girls who shared a womb with another girl, according to an analysis of hundreds of thousands of births over more than a decade. Researchers suspect the cause is testosterone exposure during fetal development, though the exact mechanism remains a mystery. “I think it’s a really interesting look at how this really complicated system might impact females,” says Talia Melber, a biological anthropologist at the University of Illinois in Urbana who wasn’t involved in the study. Still, she cautions, a lot more work needs to be done to establish a causal link. Fraternal twins, in which each of two eggs is fertilized by a different sperm cell, occur in about four of every 1000 births. About half of those result in male-female twin pairs. Typically, about 8 to 9 weeks into gestation, a male fetus begins to produce massive amounts of testosterone, which helps jump-start the development of male reproductive organs and brain architecture; female fetuses receive only modest amounts of the sex hormone. In male-female twins, though, small amounts of the male fetus’s testosterone can seep into the female twin’s separate amniotic sac. Scientists have known about this phenomenon for decades, and have been arguing for just as long over what effects, if any, it has on women later in life. © 2019 American Association for the Advancement of Science

Keyword: Sexual Behavior
Link ID: 26051 - Posted: 03.19.2019

GPs are urging women not to be alarmed by research linking long-term hormone replacement therapy (HRT) use with a small increased risk of Alzheimer's. They say HRT is an effective and safe treatment for most women with menopause symptoms and the risk is "extremely low". The BMJ research looked at data on 170,000 women in Finland over 14 years. It found a 9%-17% increased risk for Alzheimer's, particularly in women taking HRT for more than 10 years. This equates to between nine and 18 extra cases of the disease per year in every 10,000 women aged between 70 and 80, the researchers said. But the study was observational and, as a result, it cannot be said for certain that other factors had not affected the results. Other studies have found that HRT actually improves brain function. The Royal College of GPs said the research does not prove that HRT causes Alzheimer's disease, and women currently taking it should continue to do so. Prof Helen Stokes-Lampard, chairwoman of the College, said: "Hormone replacement therapy can be of greatest benefit to many women who are suffering from some of the unpleasant side-effects of the menopause, such as hot flushes and night sweats - and there is a large body of evidence that shows it is an effective and safe treatment for most women. "We would urge patients not to be alarmed by this research - as the researchers state, any risk is extremely low - and if they are currently taking HRT, to continue doing so as prescribed by their doctor. " However, she said there were risks with any medication and it was important that women were aware of them. "To minimise any risk, best practice for most women is to prescribe the lowest possible dose of hormones for the shortest possible time in order to achieve satisfactory relief of symptoms," Prof Stokes-Lampard said. © 2019 BBC

Keyword: Alzheimers; Hormones & Behavior
Link ID: 26015 - Posted: 03.07.2019

By Elizabeth Pennisi Cowbirds are the quintessential deadbeat parents. They, and about 90 other bird species, abandon their eggs in other birds’ nests, leaving the burden of chick care to others. An arms race is the result: Cuckolded foster parents keep evolving ways to fight back, and deadbeats evolve countermeasures. Now, researchers have discovered how spots on an egg play a crucial role in a parent’s decision to keep an egg—or boot it from the nest. One of the shiny cowbird’s (Molothrus bonariensis) most common victims is the chalk-browed mockingbird (Mimus saturninus). The mockingbird’s eggs are blue-green and spotted, whereas the cowbird’s eggs vary from pure white to brown and spotted. Researchers had assumed mockingbirds reject cowbird eggs that don't look like their own, in pattern and color. But the new study finds it’s not that simple. To get a better sense of how mockingbirds decide which eggs to boot, evolutionary ecologist Daniel Hanley at Long Island University in Brookville, New York, and colleagues painted 70 3D-printed eggs a range of colors and put spots on half of them. They distributed these eggs among 85 mockingbird nests and checked several days later to see which eggs were still there. Spots tended to make the mockingbirds hedge their bets and keep an egg, even if the color wasn’t “right,” Hanley and his colleagues report in the April issue of the Philosophical Transactions of the Royal Society B. For example, the mockingbirds removed unspotted brown eggs—a “wrong” color and pattern—90% of the time. But the birds were less sure when the egg had spots. They removed brown eggs with spots just 60% of the time, for example. In general, mockingbirds were more accepting of very blue eggs, even those that were much bluer than their own eggs. And when these blue eggs had spots, parents kept them more than 90% of the time. © 2019 American Association for the Advancement of Science

Keyword: Sexual Behavior; Evolution
Link ID: 26014 - Posted: 03.07.2019

Laura Sanders In the understory of Central American cloud forests, musical mice trill songs to one another. Now a study of the charismatic creatures reveals how their brains orchestrate these rapid-fire duets. The results, published in the March 1 Science, show that the brains of singing mice split up the musical work. One brain system directs the patterns of notes that make up songs, while another coordinates duets with another mouse, which are carried out with split-second precision. The study suggests that “a quirky animal from the cloud forest of Costa Rica could give us a brand new insight,” into the rapid give-and-take in people’s conversations, says study coauthor Michael Long, a neuroscientist at New York University’s School of Medicine. Quirks abound in these mice, known as Alston’s singing mice (Scotinomys teguina). Like famous singers with extreme green room demands, these mice are “kind of divas,” Long says, requiring larger terrariums, exercise equipment and a very special diet. In the lab, standard mouse chow doesn’t cut it; instead, singing mice feast on fresh meal worm, dry cat food and fresh fruits and berries, says Bret Pasch. The biologist at Northern Arizona University in Flagstaff has studied these singing mice for years but wasn’t involved in this study. The mice are also, of course, loud. “They’re very vocal,” particularly in the confines of a lab, Pasch says. “Once an animal calls, it’s like a symphony that goes off,” with repeating calls. In the wild, these duets are thought to attract mates and stake out territory. |© Society for Science & the Public 2000 - 2019.

Keyword: Animal Communication; Sexual Behavior
Link ID: 25998 - Posted: 03.01.2019

Nicola Davis A pair of twins have stunned researchers after it emerged that they are neither identical nor fraternal – but something in between. The team say the boy and girl, now four years old, are the second case of semi-identical twins ever recorded, and the first to be spotted while the mother was pregnant. The situation was a surprise to the researchers. An ultrasound of the 28-year old mother at six weeks suggested the twins were identical – with signs including a shared placenta. But it soon became clear all was not as it seemed. “What happened was the mother came back for her routine ultrasound some months later, and we saw one [twin] to be a boy and one to be a girl,” said Dr Michael Gabbett, first author of the report from Queensland University of Technology in Australia. “At that point we started the genetic studies and worked it out from there.” Twins are normally either identical or fraternal. In the case of identical, one egg is fertilised by one sperm, but the resulting ball of cells splits in two, giving rise to two offspring with identical genetic material. In the case of fraternal, or non-identical, twins, two eggs are fertilised, each by a different sperm. The resulting siblings arise from the same pregnancy, but are no more genetically similar than siblings from the same parents born at a different time. Faced with a puzzling scenario, Gabbett and colleagues report in the New England Journal of Medicine that they took samples from the two amniotic sacs, allowing them to investigate the genomes of the twins during the pregnancy. © 2019 Guardian News & Media Limited

Keyword: Sexual Behavior; Development of the Brain
Link ID: 25997 - Posted: 03.01.2019

Susan Milius Cheating pays, sort of. But for a glossy blue-black bird with a bright yellow eye, cheating doesn’t outdo regular honest parenting. The greater ani, a type of cuckoo found from Panama to the Amazon Basin, usually starts out as a dutiful parent. Two or three male-female pairs typically build and fill a communal nest “like a big basket of eggs,” says behavioral ecologist Christina Riehl of Princeton University. But if a snake or some other disaster kills the young, a bereft female sometimes gets sneaky. She slips into neighboring ani nests and leaves an egg here and there that she won’t care for, but the rightful nest owners might. Not all females from trashed nests do that. Some just wait for the next breeding season, when all the birds get a fresh start building another nest. Greater anis’ sporadic cheating offers a rare chance to compare the success of egg-sneaks with honest mothers in the same species. Over 11 breeding seasons, Riehl and colleagues determined the parentage of more than 1,700 eggs and found 65 eggs in foster nests. Mothers that parasitize other nests in this way seem to lay more eggs a year, on average, Riehl says. “It’s actually kind of hard to be a parasite,” she says. But the average number of chicks that survived to flutter out of the nest on their own frantic wing power was about the same for all females, Riehl and Princeton colleague Meghan Strong report online February 27 in Nature. The mothers that always cooperated averaged about one fledgling a year, and so did the females that laid stealth eggs. |© Society for Science & the Public 2000 - 2019

Keyword: Sexual Behavior; Evolution
Link ID: 25991 - Posted: 02.28.2019