Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases
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By Alice Klein Who needs men? A female shark separated from her long-term mate has developed the ability to have babies on her own. Leonie the zebra shark (Stegostoma fasciatum) met her male partner at an aquarium in Townsville, Australia, in 1999. They had more than two dozen offspring together before he was moved to another tank in 2012. From then on, Leonie did not have any male contact. But in early 2016, she had three baby sharks. Intrigued, Christine Dudgeon at the University of Queensland in Brisbane, Australia, and her colleagues began fishing for answers. Zoologger: The amphibious fish that mates with itself One possibility was that Leonie had been storing sperm from her ex and using it to fertilise her eggs. But genetic testing showed that the babies only carried DNA from their mum, indicating they had been conceived via asexual reproduction. Some vertebrate species have the ability to reproduce asexually even though they normally reproduce sexually. These include certain sharks, turkeys, Komodo dragons, snakes and rays. However, most reports have been in females who have never had male partners. There are very few reports of asexual reproduction occurring in females with previous sexual histories, says Dudgeon. An eagle ray and a boa constrictor, both in captivity, are the only other female animals that have been documented switching from sexual to asexual reproduction. © Copyright Reed Business Information Ltd.
Keyword: Sexual Behavior
Link ID: 23110 - Posted: 01.17.2017
By Virginia Morell Only three known species go through menopause: killer whales, short-finned pilot whales, and humans. Two years ago, scientists suggested whales do this to focus their attention on the survival of their families rather than on birthing more offspring. But now this same team reports there’s another—and darker—reason: Older females enter menopause because their eldest daughters begin having calves, leading to fights over resources. The findings might also apply to humans, the scientists say. “What an interesting paper,” says Phyllis Lee, a behavioral ecologist at the University of Stirling in the United Kingdom, who was not involved in the study. “It brings two perspectives on menopause neatly together, and provides an elegant model for its rarity.” The new work came about when Darren Croft, a behavioral ecologist at the University of Exeter in the United Kingdom, and his colleagues looked back on their 2015 killer whale menopause study. “That showed how they helped and why they lived so long after menopause, but it didn’t explain why they stop reproducing,” he says, noting that in other species, such as elephants, older females also share wisdom and knowledge with their daughters, but continue to have calves. © 2017 American Association for the Advancement of Science.
By Alice Klein Mothers hold their children more on the left and wild mammals seem to keep their young more on that so too, at least when fleeing predators. Now it seems many mammal babies prefer to approach their mother from one side too – and the explanation may lie in the contrasting talents of each half of the brain. In mammals, the brain’s right hemisphere is responsible for processing social cues and building relationships. It is also the half of the brain that receives signals from the left eye. Some researchers think this explains why human and ape mothers tend to cradle their babies on the left: it is so they can better monitor their facial expressions with their left eye. Now, Janeane Ingram at the University of Tasmania, Australia, and her colleagues have looked at whether animal infants also prefer to observe their mum from one side. The team studied 11 wild mammals from around the world: horses, reindeer, antelopes, oxen, sheep, walruses, three species of whale and two species of kangaroo. Whenever an infant approached its mother from behind, the researchers noted whether it positioned itself on its mum’s left or right side. They recorded almost 11,000 position choices for 175 infant-mother pairs. Infants of all species were more likely to position themselves so that their mother was on their left. This happened about three-quarters of the time. © Copyright Reed Business Information Ltd.
By Virginia Morell Japanese macaques and sika deer live comfortably together on Japan’s Yakushima Island: The deer eat fruit the monkeys drop from the trees, and the monkeys groom and sometimes hitch a ride on the deer. But a couple years ago, one of the macaques took this relationship to a new level. Unable to get a mate of his own kind, this low-ranking snow monkey used the deer’s back for his pleasure (as pictured, and also shown in this not-suitable-for-work video). He did not penetrate her, but did ejaculate, and the deer then licked her back clean, researchers report in the current issue of Primates. The monkey was later seen attempting to mount another deer, but she objected and threatened him. He also guarded his unlikely love interests, chasing away any other male monkeys who came near. Scientists have only reported one other case of sexual relations in the wild between unrelated species. That one involved male Antarctic fur seals coercing king penguins; once, after sating his lust, the seal ate the bird. In both cases, scientists suspect that the males were unable to acquire a mate of their own kind, and seasonal hormonal surges led them to seek love elsewhere. © 2017 American Association for the Advancement of Science.
Keyword: Sexual Behavior
Link ID: 23074 - Posted: 01.10.2017
By Ellen Hendriksen Pop quiz: what’s the first thing that comes to mind when I say “ADHD”? a. Getting distracted b. Ants-in-pants c. Elementary school boys d. Women and girls Most likely, you didn’t pick D. If that’s the case, you’re not alone. For most people, ADHD conjures a mental image of school-aged boys squirming at desks or bouncing off walls, not a picture of adults, girls, or especially adult women. Both scientists and society have long pinned ADHD on males, even though girls and women may be just as likely to suffer from this neurodevelopmental disorder. Back in 1987, the American Psychiatric Association stated that the male to female ratio for ADHD was 9 to 1. Twenty years later, however, an epidemiological study of almost 4,000 kids found the ratio was more like 1 to 1—half girls, half boys. © 2017 Scientific American
National Institutes of Health (NIH) researchers have discovered molecular mechanisms that may underlie a woman’s susceptibility to disabling irritability, sadness, and anxiety in the days leading up to her menstrual period. Such premenstrual dysphoric disorder (PMDD) affects 2 to 5 percent of women of reproductive age, whereas less severe premenstrual syndrome (PMS) is much more common. “We found dysregulated expression in a suspect gene complex which adds to evidence that PMDD is a disorder of cellular response to estrogen and progesterone,” explained Peter Schmidt, M.D. of the NIH’s National Institute of Mental Health, Behavioral Endocrinology Branch. “Learning more about the role of this gene complex holds hope for improved treatment of such prevalent reproductive endocrine-related mood disorders.” Schmidt, David Goldman, M.D., of the NIH’s National Institute on Alcohol Abuse and Alcoholism, and colleagues, report on their findings January 3, 2017 in the journal Molecular Psychiatry. “This is a big moment for women’s health, because it establishes that women with PMDD have an intrinsic difference in their molecular apparatus for response to sex hormones – not just emotional behaviors they should be able to voluntarily control,” said Goldman. By the late 1990s, the NIMH team had demonstrated (link is external) that women who regularly experience mood disorder symptoms just prior to their periods were abnormally sensitive to normal changes in sex hormones — even though their hormone levels were normal. But the cause remained a mystery.
By Alice Callahan Can psychiatric medications alter the mother-baby bond? I am having a baby in a month and am on an antidepressant, antipsychotic and mood stabilizer. I don't feel a natural instinct to mother or connect to my baby yet. Could it be because of my medications? It’s normal for expectant parents to worry if they don’t feel a strong connection to the baby right away. “Those kinds of mixed fears and anxieties are really common in most pregnancies, certainly first pregnancies,” said Dorothy Greenfeld, a licensed clinical social worker and professor of obstetrics and gynecology at Yale School of Medicine. Bonding is a process that takes time, and while it can begin in pregnancy, the relationship between parent and child mostly develops after birth. Psychiatric conditions, and the medicines used to treat them, can complicate the picture. Antidepressants, the most widely used class of psychiatric drugs, do not seem to interfere with a woman’s attachment to the fetus during pregnancy, as measured by the amount of time the mother spends thinking about and planning for the baby, a 2011 study in the Archives of Women’s Mental Health found. On the other hand, the study found that women with major depression in pregnancy had lower feelings of maternal-fetal attachment, and this sense of disconnection intensified with more severe symptoms of depression. “Depression can definitely affect a person’s ability to bond with their baby, to feel those feelings of attachment, which is why we encourage treatment so strongly,” said Dr. Amy Salisbury, the study leader and a professor of pediatrics and psychiatry at the Alpert Medical School at Brown University. “That’s more likely to interfere than the medication itself.” There is less research on the effects of other types of mental health medications on mother-baby bonding, but psychiatric medications can have side effects that might interfere with parenting. For example, a small percentage of people taking mood-stabilizing medications have feelings of apathy, and that could hinder the bonding process, said Dr. Salisbury. And some mental health medications, depending on dosage and combination, might make a person feel too sedated. But again, letting mental illness go untreated is likely far riskier for both the mother and the baby. © 2016 The New York Times Company
By Laura Beil, Justin Shamoun began to hate his body a few weeks into seventh grade. He was a year younger than his suburban Detroit classmates, having skipped a grade. Many of his peers were entering puberty, their bodies solidifying into sleek young men. Justin still had the doughy build of a boy. After gym class one day, someone told Justin he could probably run faster if he weren’t so fat. The remark crushed him. Ashamed, he started hiding his body under ever-baggier clothes and making excuses to skip P.E., the pool, anywhere required to expose bare skin. Finally, he decided to fix himself. He dove headlong into sports and cut back on food. Before long, he was tossing his lunch into the garbage and picking at his dinner. He ate just enough to blunt his hunger, until the time came when he ate barely at all. The thought that he had an eating disorder never occurred to him. Long considered an affliction of women, eating disorders — the most deadly of all mental illnesses — are increasingly affecting men. The National Eating Disorders Association predicts that 10 million American men alive today will be affected, but that number is only an estimate based on the limited research available. The official criteria for diagnosing eating disorders were updated to be more inclusive of men only in 2013. And last year, Australian researchers writing in the Journal of Eating Disorders noted that “the prevalence of extreme weight control behaviors, such as extreme dietary restriction and purging” may be increasing at a faster rate in men than women. © 2016 Scientific American
By Heather M. Snyder For more than 25 years, Mary Read was a successful nurse in Lititz, Pennsylvania. But in 2010, at the age of 50, she started having trouble with her memory and thinking, making it difficult for her to complete routine tasks and follow instructions at work. The problems worsened, bringing her career to an abrupt end. In 2011, her doctor conducted a comprehensive evaluation, including a cognitive assessment, and found that she was in the early stages of younger-onset Alzheimer’s, which affects hundreds of thousands of people under 65. A year earlier, Elizabeth Wolf faced another sort of upheaval. The 36-year-old community health program director was forced to abandon her own career, home and community in Vermont when both of her parents were diagnosed with Alzheimer’s three months apart. Wolf took the difficult decision to move back into her childhood home in Mount Laurel, New Jersey in order to become their primary caregiver. These stories are not unusual. Alzheimer’s dementia disproportionately affects women in a variety of ways. Compared with men, 2.5 times as many women as men provide 24-hour care for an affected relative. Nearly 19 percent of these wives, sisters and daughters have had to quit work to do so. In addition, women make up nearly two-thirds of the more than 5 million Americans living with Alzheimer’s today. According to the Alzheimer’s Association 2016 Alzheimer’s Disease Facts and Figures, an estimated 3.3 million women aged 65 and older in the United States have the disease. To put that number in perspective, a woman in her sixties is now about twice as likely to develop Alzheimer’s as breast cancer within her lifetime. © 2016 Scientific American
Morwenna Ferrier Is my face attractive? Don’t answer that. Not because I’m ducking out of this, but because you can’t. Attractiveness is subjective, perhaps the most subjective question of all; that we outsource the answer to Google (and we do, in our droves) is ironic since it depends on a bias that is impossible to unpack. Yet in searching the internet for an answer, it also reveals the question to be one of the great existential tensions of our time. Because, as we all know, being attractive is absolutely 100% the A-road to happiness. If you are Googling to rate your attractiveness, then you are probably working on the assumption that you aren’t. You’re also, possibly, more vulnerable and susceptible to being told that you aren’t. In short, you’re a sitting duck, someone who had a sore throat and who asked good old Dr Google for advice only to be told it was cancer. Still, it’s only in investigating precisely why Google is the last person you should ask – being a search engine therefore insentient – that you can start cobbling together an idea of what attractiveness really is. It’s worth starting with semantics. Beauty is not attractiveness and vice versa, though we commonly confuse the two. Beauty (arguably) has a template against which we intuit and against which we measure ourselves. It is hinged around genetics and a particular look associated with this politically correct (and largely western-governed) model. Darwin wouldn’t agree: “It is certainly not true that there is in the mind of man any universal standards of beauty with respect to the human body,” he said. But a lot has changed since his time. © 2016 Guardian News and Media Limited
Keyword: Sexual Behavior
Link ID: 23030 - Posted: 12.28.2016
Laura Sanders Pregnancy changes nearly everything about an expectant mother’s life. That includes her brain. Pregnancy selectively shrinks gray matter to make a mom’s brain more responsive to her baby, and those changes last for years, scientists report online December 19 in Nature Neuroscience. “This study, coupled with others, suggests that a women’s reproductive history can have long-lasting, possibly permanent changes to her brain health,” says neuroscientist Liisa Galea of the University of British Columbia in Vancouver, who was not involved in the study. Researchers performed detailed anatomy scans of the brains of 25 women who wanted to get pregnant with their first child. More scans were performed about two months after the women gave birth. Pregnancy left signatures so strong that researchers could predict whether women had been pregnant based on the changes in their brains. The women who had carried a child and given birth had less gray matter in certain regions of their brains compared with 20 women who had not been pregnant, 19 first-time fathers and 17 childless men. These changes were still evident two years after pregnancy. A shrinking brain sounds bad, but “reductions in gray matter are not necessarily a bad thing,” says study coauthor Elseline Hoekzema, a neuroscientist at Leiden University in the Netherlands. A similar reduction happens during adolescence, a refinement that is “essential for a normal cognitive and emotional development,” says Hoekzema, who, along with colleagues, did most of the work at Universitat Autònoma de Barcelona. Following those important teenage years, pregnancy could be thought of almost as a second stage of brain maturing, she says. |© Society for Science & the Public 2000 - 2016.
By Claire Asher We pride ourselves on our big brains, but when it comes to figuring out whether people or other animals with particularly big brains do better than others, the evidence has been lacking. Now, for the first time, a study in red deer is showing that bigger brained mammals tend to be more successful in the wild, and that brain size is a heritable trait that they can pass on to their offspring. Corina Logan from the University of Cambridge and her team have looked at the skulls of 1314 red deer (Cervus elaphus) from the Isle of Rum. The complete life histories of the deer are well known thanks to the Isle of Rum Red Deer Project, which has been collecting data on the island for more than 40 years, spanning seven deer generations. “This kind of study has not been conducted before because it requires long-term data from a large number of individuals,” says Logan. Heritable heads The team found that the ratio of skull volume to body size was highly heritable, explaining 63 per cent of variation between individuals. Female deer with larger skulls lived significantly longer and raised more offspring to adulthood, though it’s not clear yet why bigger brains are advantageous to females. © Copyright Reed Business Information Ltd.
By Sam Wong Size matters. Bigger genitals mean more mating success for male mosquito fish, a relative of the guppy. But the development of longer male organs prompts females to evolve bigger brains to help them escape overeager mates. Mating among mosquito fish is far from romantic. The male makes no effort to court partners, instead sneaking up and attempting to copulate by force up to a thousand times a day. It uses a modified anal fin, the gonopodium, to deliver sperm into the female. In this sort of mating system, the relationship between males and females can resemble that between predators and prey, which commonly involve an evolutionary arms race where adaptations on one side are closely matched by changes on the other. For example, big-brained predators tend to prey on big-brained prey, as the two try to outsmart each other. Séverine Buechel and colleagues at Stockholm University in Sweden wondered if a similar arms race was going on between male and female mosquito fish. Do females evolve bigger brains to defend against sneaky males, and do males evolve bigger brains in response? To test this, the team looked at what happened to brain size when males were bred to have longer gonopodia. Male mosquito fish have long gonopodia compared with related species in which coercion is not the dominant mating strategy, and males with longer gonopodia tend to be more successful at mating. The researchers found that breeding more well-endowed males led to bigger-brained females. But there was no arms race: male brains didn’t get bigger at the same time. © Copyright Reed Business Information Ltd.
Barbara J. King Birdsong is music to human ears. It has inspired famous composers. For the rest of us, it may uplift the spirit and improve attention or simply be a source of delight, fun and learning. But have you ever wondered what birds themselves hear when they sing? After all, we know that other animals' perceptions don't always match ours. Anyone who lives with a dog has probably experienced their incredible acute hearing and smell. Psychologists Robert J. Dooling and Nora H. Prior think they've found an answer to that question — for, at least, some birds. In an article published online last month in the journal Animal Behaviour, they conclude that "there is an acoustic richness in bird vocalizations that is available to birds but likely out of reach for human listeners." Dooling and Prior explain that most scientific investigations of birdsong focus on things like pitch, tempo, complexity, structural organization and the presence of stereotypy. They instead focused on what's called temporal fine structure and its perception by zebra finches. Temporal fine structure, they write, "is generally defined as rapid variations in amplitude within the more slowly varying envelope of sound." Struggling to fully grasp that definition, I contacted Robert Dooling by email. In his response, he suggested that I think of temporal fine structure as "roughly the difference between voices when they are the same pitch and loudness." Temporal fine structure is akin, then, to timbre, sometimes defined as "tone color" or, in Dooling's words, the feature that's "left between two complex sounds when the pitch and level are equalized." © 2016 npr
By Clare Wilson Could a brain stimulation device change our sex drive? The first study of this approach suggests that people’s libido can be turned up or down, depending on the device’s setting. The study didn’t measure how much sex people had in real life, instead it measured participant’s sexual responsiveness. Unusually, this was done by fixing customised vibrators to people’s genitals and gauging how their brainwaves changed when they expected a stimulating buzz. “You want to see if they want what you’re offering,” says Nicole Prause at the University of California, Los Angeles. “This is a good model for sexual desire.” The technique involves transcranial magnetic stimulation (TMS), where a paddle held above the head uses a strong magnetic field to alter brain activity. It can be used to treat depression and migraines, and is being investigated for other uses, including preventing bed-wetting, and helping those with dyslexia. The part of the head targeted in this study – called the left dorsolateral prefrontal cortex, roughly above the left temple – is involved in the brain’s reward circuitry. © Copyright Reed Business Information Ltd.
Keyword: Sexual Behavior
Link ID: 22936 - Posted: 12.01.2016
Carrie Arnold There was one sound that biologist Rusty Gonser always heard at Cranberry Lake — and there was one sound that he would never hear again. Every summer for more than 25 years, Gonser and his wife, Elaina Tuttle, had made the trip to this field station in the Adirondack Mountains — a 45-minute boat ride from the nearest road. Now, as he moored his boat to the shaky wooden dock, he heard a familiar and short song that sounded like 'oh-sweet-Canada'. The whistle was from a white-throated sparrow calling hopefully for a mate. What he didn't hear was the voice or laughter of his wife. For the first time, Gonser was at Cranberry Lake alone. Just a few weeks earlier, Tuttle had died of breast cancer. Her entire career, and most of Gonser's, had been devoted to understanding every aspect of the biology of the white-throated sparrow (Zonotrichia albicollis). Less than six months before she died this year at the age of 52, the couple and their team published a paper1 that was the culmination of that work. It explained how a chance genetic mutation had put the species on an extraordinary evolutionary path. The mutation had flipped a large section of chromosome 2, leaving it unable to pair up with a partner and exchange genetic information. The more than 1,100 genes in the inversion were inherited together as part of a massive 'supergene' and eventually drove the evolution of two different 'morphs' — subtypes of the bird that are coloured differently, behave differently and mate only with the opposite morph. Tuttle and Gonser's leap was to show that this process is nearly identical to the early evolution of certain sex chromosomes, including the human X and Y. The researchers realized that they were effectively watching the bird evolve two sex chromosomes, on top of the two it already had. © 2016 Macmillan Publishers Limited,
By Usha Lee McFarling, There’s something wrong with the brain banks created to study the dangers of repeated trauma to the head: Almost all the brains donated so far belonged to men. It’s just one example of how the study of brain trauma in women lags behind—even though women get concussions at higher rates than men in many sports and may suffer more severe and persistent symptoms. “If concussion is the invisible injury, then females are the invisible population within that injury,” said Katherine Snedaker, a licensed clinical social worker from Norwalk, Conn., who founded the nonprofit PINK Concussions in 2013 to focus attention on the issue. Evidence is building that the response to traumatic injury is different enough in females that they might benefit from gender-specific treatment, as they do with cardiac disease. But the data to create such guidelines simply aren’t there. “It’s an incredible gap in our knowledge,” said Angela Colantonio, director of the Rehabilitation Science Institute at the University of Toronto. “It’s just not acceptable.” When Colantonio examined 200 studies on prognosis after mild traumatic brain injury, she found only 7 percent separated out women. And if female athletes are overlooked, other groups vulnerable to concussion—aging women, women in prison, and domestic abuse survivors—have been nearly entirely ignored. © 2016 Scientific American
Ramin Skibba Bats sing just as birds and humans do. But how they learn their melodies is a mystery — one that scientists will try to solve by sequencing the genomes of more than 1,000 bat species. The project, called Bat 1K, was announced on 14 November at the annual meeting of the Society for Neuroscience in San Diego, California. Its organizers also hope to learn more about the flying mammals’ ability to navigate in the dark through echolocation, their strong immune systems that can shrug off Ebola and their relatively long lifespans. “The genomes of all these other species, like birds and mice, are well-understood,” says Sonja Vernes, a neurogeneticist at the Max Planck Institute for Psycholinguistics in Nijmegen, Netherlands, and co-director of the project. “But we don’t know anything about bat genes yet.” Some bats show babbling behaviour, including barks, chatter, screeches, whistles and trills, says Mirjam Knörnschild, a behavioural ecologist at Free University Berlin, Germany. Young bats learn the songs and sounds from older male tutors. They use these sounds during courtship and mating, when they retrieve food and as they defend their territory against rivals. Scientists have studied the songs of only about 50 bat species so far, Knörnschild says, and they know much less about bat communication than about birds’. Four species of bats have so far been found to learn songs from each other, their fathers and other adult males, just as a child gradually learns how to speak from its parents1. © 2016 Macmillan Publishers Limited,
By CHRIS BUCKLEY BEIJING — When Flappy McFlapperson and Skybomb Bolt sprang into the sky for their annual migration from wetlands near Beijing, nobody was sure where the two cuckoos were going. They and three other cuckoos had been tagged with sensors to follow them from northern China. But to where? “These birds are not known to be great fliers,” said Terry Townshend, a British amateur bird watcher living in the Chinese capital who helped organize the Beijing Cuckoo Project to track the birds. “Migration is incredibly perilous for birds, and many perish on these journeys.” The answer to the mystery — unfolding in passages recorded by satellite for more than five months — has been a humbling revelation even to many experts. The birds’ journeys have so far covered thousands of miles, across a total of a dozen countries and an ocean. The “common cuckoo,” as the species is called, turns out to be capable of exhilarating odysseys. “It’s impossible not to feel an emotional response,” said Chris Hewson, an ecologist with the British Trust for Ornithology in Thetford, England, who has helped run the tracking project. “There’s something special about feeling connected to one small bird flying across the ocean or desert.” But to follow a cuckoo, you must first seduce it. The common cuckoo is by reputation a cynical freeloader. Mothers outsource parenting by laying their eggs in the nests of smaller birds, and the birds live on grubs, caterpillars and similar soft morsels. British and Chinese bird groups decided to study two cuckoo subspecies found near Beijing, because their winter getaways were a puzzle. In an online poll for the project, nearly half the respondents guessed they went somewhere in Southeast Asia. © 2016 The New York Times Company
Very stressful events affect the brains of girls and boys in different ways, a Stanford University study suggests. A part of the brain linked to emotions and empathy, called the insula, was found to be particularly small in girls who had suffered trauma. But in traumatised boys, the insula was larger than usual. This could explain why girls are more likely than boys to develop post-traumatic stress disorder (PTSD), the researchers said. Their findings suggest that boys and girls could display contrasting symptoms after a particularly distressing or frightening event, and should be treated differently as a result. The research team, from Stanford University School of Medicine, said girls who develop PTSD may actually be suffering from a faster than normal ageing of one part of the insula - an area of the brain which processes feelings and pain. Image copyright Science Photo Library Image caption The insula, also known as the insular cortex, is linked to the body's experience of pain or emotional experiences of fear The insula, or insular cortex, is a diverse and complex area, located deep within the brain which has many connections. As well as processing emotions, it plays an important role in detecting cues from other parts of the body. The researchers scanned the brains of 59 children aged nine to 17 for their study, published in Depression and Anxiety. © 2016 BBC.