Chapter 8. Hormones and Sex

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by Clare Wilson More genetic mutations may be needed to give rise to autism in girls than in boys. The finding supports the notion that the female brain is somehow protected against autism, and this may in turn explain why four times as many males have autism than females. Although some cases of autism are associated with one mutation, most are thought to involve several genetic abnormalities. In the past few years, hundreds of mutations have been discovered that can make people more vulnerable to the condition. To see if the mutations affect men and women differently, Sébastien Jacquemont at the University Hospital of Lausanne in Switzerland and colleagues measured the frequency of two different kinds of mutation in 762 families that had a child with autism. Among the children with autism, one class of mutation known as a copy number variation – deletions or duplications of a large chunk of genetic material – was three times more common in girls than in boys. The team also found that substitutions of a single letter of DNA were about one-third more common in affected girls. Jacquemont says this suggests it takes more mutations for autism to arise in girls than in boys. "Females function a lot better than males with similar mutations," he says. The results reflect the "shielding" effect of being female, he says. "There's something that's protecting [their] brain development." A larger, as yet unpublished, study of about 2400 people with autism, conducted as part of the Autism Genome Project - an attempt to sequence the whole genome of 10,000 individuals affected by the condition – has produced similar results, says Joseph Buxbaum of Mount Sinai Hospital in New York. © Copyright Reed Business Information Ltd.

Keyword: Autism; Aggression
Link ID: 19311 - Posted: 03.01.2014

Sara Reardon A flipped mental switch is all it takes to make a fly fall in love — even if its object of desire is a ball of wax. A technique called thermogenetics allows researchers to control fly behaviour by activating specific neurons with heat. Combining the system with techniques that use light to trigger neurons could help to elucidate how different neural circuits work together to control complex behaviours such as courtship. Optogenetics — triggering neurons with light — has been successful in mice but has not been pursued much in flies, says Barry Dickson, a neuroscientist at the Howard Hughes Medical Institute's Janelia Farm Research Campus in Ashburn, Virginia. A fibre-optic cable embedded in a mouse’s brain can deliver light to cells genetically engineered to make light-activated proteins, but flies are too small for these fibre optics. Neither will these cells be activated when the flies are put into an illuminated box, because most wavelengths of visible light cannot penetrate a fly’s exoskeleton. Heat can penetrate the exoskeleton, however. Researchers have already studied fly behaviour by adding a heat-activated protein called TRPA1 to neural circuits that control behaviours such as mating and decision-making. When these flies are placed in a hot box, the TRPA1 neurons begin to fire within minutes and drive the fly’s actions1. But it would be better to trigger the behaviours more quickly. So Dickson’s lab has developed a system called the Fly Mind-Altering Device (FlyMAD), which uses a video camera to track the fly as it moves around in a box. The device then shines an infrared laser at the fly to deliver heat directly to the head. Dickson’s group presented the system last October at the Neurobiology of Drosophila conference at Cold Spring Harbor Laboratory in New York, and he is now submitting the work to a peer-reviewed journal. © 2014 Nature Publishing Group

Keyword: Sexual Behavior; Aggression
Link ID: 19310 - Posted: 03.01.2014

Carl Zimmer Forcing male flies into monogamy has a startling effect: After a few dozen generations, the flies become worse at learning. This discovery, published on Wednesday in the Proceedings of the Royal Society, isn’t a biological excuse for men who have strayed from their significant other. Instead, it’s a tantalizing clue about why intelligence evolved. The new study was carried out by Brian Hollis and Tadeusz J. Kawecki, biologists at the University of Lausanne in Switzerland. They investigated a fly species called Drosophila melanogaster that normally has a very un-monogamous way of life. To find a mate, the male flies seek out females on rotting pieces of fruit. They often engage in battles to chase their rivals away, and then pick a female to court. “The males will do this wing song, where they use one wing or the other to generate a song,” said Dr. Hollis. This wing song may last from 10 minutes to an hour. Virgin females usually accept the overtures. But if a female has just mated, she will reject a new male’s advances. “If a male comes at her from behind and she’s not interested, she’ll kick at him with her rear legs,” said Dr. Hollis. If a couple of days have passed since her last mating, however, the female may choose to mate again. Seven years ago, while he was a graduate student at Florida State University, Dr. Hollis set out to study how the competition among males shapes their evolution. He began breeding two groups of flies — one polygamous, the other monogamous. In 2011, he took his flies to the University of Lausanne, where he met Dr. Kawecki, an expert on learning. The two scientists wondered if the different mating habits of Dr. Hollis’s flies had altered their brains. © 2014 The New York Times Company

Keyword: Sexual Behavior; Aggression
Link ID: 19309 - Posted: 03.01.2014

Brian Owens The distinctive aroma of goats does more than just make barnyards extra fragrant. Male goats can use their heady scent to make female goats ovulate simply by being near them. Researchers had ascribed this 'male effect' to chemicals known as primer pheromones — a chemical signal that can cause long-lasting physiological responses in the recipient. Examples of primer pheromones are rare in mammals; the male effect in goats and sheep, and a similar effect in mice and rats, where the presence of males can speed up puberty in females, are the only known cases. But exactly what substances are at work and how has remained a mystery. Now, reproductive biologist Yukari Takeuchi from the University of Tokyo and her colleagues have identified a single molecule, known as 4-ethyloctanal, in the cocktail of male goat pheromones that activates the neural pathway that regulates reproduction in females1. ”It has long been thought that pheromones have pivotal roles in reproductive success in mammals, but the mechanisms are scarcely known,” says Takeuchi. The researchers found that male goat pheromones are generally synthesized in the animal's head skin, so they designed a hat containing a material that captured their odorous molecules and placed them on the goats for a week to collect the scent. Analysis of the gases collected identified a range of compounds, many of which were unknown and were not present in castrated males. When exposed to a cocktail of 18 of these chemicals, the brains of female goats showed a sudden increase in the activity of the gonadotropin-releasing hormone (GnRH) pulse generator — the neural regulator of reproduction. © 2014 Nature Publishing Group,

Keyword: Chemical Senses (Smell & Taste); Aggression
Link ID: 19308 - Posted: 03.01.2014

On 24 February, Uganda’s president, Yoweri Museveni, signed a draconian Anti-Homosexuality Bill into law, after 2 months of declining to do so. Science, he says, changed his mind—in particular, the findings of a special scientific committee his Health Ministry had appointed earlier in the month. “Their unanimous conclusion was that homosexuality, contrary to my earlier thinking, was behavioural and not genetic,” Museveni wrote to President Barack Obama on 18 February, in response to Obama’s pleas that he not sign the bill. “It was learnt and could be unlearnt.” But some scientists on the committee are crying foul, saying that Museveni and his ruling party—Uganda’s National Resistance Movement (NRM)—misrepresented their findings. “They misquoted our report,” says Paul Bangirana, a clinical psychologist at Makerere University in Kampala. “The report does not state anywhere that homosexuality is not genetic, and we did not say that it could be unlearnt.” Two other committee members have now resigned to protest the use of their report to justify the harsh legislation, which mandates life imprisonment for “aggravated homosexuality,” such as sexual acts with a minor, and prison terms of 7 to 14 years for attempted and actual homosexual acts, respectively. The law was first introduced into Uganda’s Parliament in 2009, but withdrawn after widespread objections to provisions that could have included the death penalty. As he signed the new version, passed by Parliament last 20 December, Museveni claimed that “mercenaries” were recruiting young people into gay activities. © 2014 American Association for the Advancement of Science

Keyword: Sexual Behavior; Aggression
Link ID: 19296 - Posted: 02.26.2014

By Sandhya Somashekhar, The Food and Drug Administration has approved 24 drugs for the treatment of male sexual dysfunction. For women, that number is zero. The disparity reflects drugmakers’ difficulties in unlocking the secret to revving up women’s sex drive. It also has become a rallying point for women’s advocates and even some members of Congress, who suggest that federal regulators seem more eager to approve sex-enhancing drugs for men than for women. It isn’t every day that political leaders and groups such as the National Organization for Women get involved in the drug- approval process, particularly for “lifestyle” drugs. But the unsuccessful quest for a “female Viagra” is sparking complicated questions about a woman’s right to a pill that may improve her sex life — and about how much of a libido lift is enough to be judged effective by the FDA. A drug called flibanserin, touted by some as the “little pink pill,” the counterpoint to Viagra’s little blue pill, was developed 12 years ago. Last month, women’s groups were disappointed when the FDA asked for further safety tests on the medication. Some critics say the agency — consciously or not — may be succumbing to society’s squeam­ishness about women’s sexual desires compared with those of men. “It looks to me like there are more hurdles being put in front of this drug than there have been on drugs addressing male dysfunction,” said Terry O’Neill, president of NOW. “Obviously, everyone only wants drugs to get on the market if they are proven safe and effective. But we don’t want attitudes to get in the way of a good drug.” © 1996-2014 The Washington Post

Keyword: Sexual Behavior
Link ID: 19274 - Posted: 02.20.2014

By PAUL VITELLO Alison Jolly, an American-born primatologist whose research in the forests of Madagascar shed new light on the evolution of social intelligence and helped disprove a longstanding scientific tenet that males were dominant in every primate species, died on Feb. 6 in Lewes, East Sussex, England. She was 76. The cause was breast cancer, said Barbara Orlando, a longtime friend. Dr. Jolly’s two major insights emerged from her 1960s field studies of the lemur, a primate whose development in relative isolation on the island of Madagascar makes the species something akin to a living fossil. Dr. Jolly cited lemurs’ complex social relationships as evidence of an unexplored trail in one of anthropology’s great mysteries: the evolution of higher intelligence. Writing in the journal Science in 1966, she suggested that the many hours lemurs spent in play, mutual grooming and social networking — activities that establish the social ties and hierarchies that determine access to food, mate selection and migration patterns — may have been as important to the evolution of intelligence as the development of weapons and tools of hunting and protection, then considered the hallmarks of evolutionary advance. More unnerving to colleagues was her discovery that in some primate species, females run the show. The finding upended a bedrock assertion in evolutionary biology — based on studies of chimpanzees and orangutans in captivity — that males dominated females in every primate species, including humans. “Females have social, spatial and feeding priority over males,” Dr. Jolly wrote in describing the feeding, mating, child-rearing and recreational habits of the ring-tailed lemur, one of about 100 recognized species of lemur, of which more than a dozen are female-dominant. Among the ring-tailed lemurs, Dr. Jolly wrote in “Lemur Behavior: A Madagascar Field Study,” “all females, whether dominant or subordinate in the female hierarchy, are dominant over males.” © 2014 The New York Times Company

Keyword: Evolution; Aggression
Link ID: 19265 - Posted: 02.19.2014

By James Gallagher Health and science reporter, BBC News A tool for predicting the risk of clinical depression in teenage boys has been developed by researchers. Looking for high levels of the stress hormone cortisol and reports of feeling miserable, lonely or unloved could find those at greatest risk. Researchers at the University of Cambridge want to develop a way of screening for depression in the same way as heart problems can be predicted. However, their method was far less useful in girls. Teenage years and early adulthood are a critical time for mental health - 75% of disorders develop before the age of 24. But there is no way to accurately say who will or will not develop depression. Risky combination Now researchers say they have taken the "first step" towards a screening tool. Tests on 1,858 teenagers, reported in Proceedings of the National Academy of Sciences, combined hormone levels and mood questionnaires to assess risk. They showed that having both high cortisol levels and depressive mood symptoms posed a higher risk of depression than either factor alone and presented a risk of clinical depression 14 times that of those with low cortisol and no depressive symptoms. Around one in six boys was in the high-risk category and half of them were diagnosed with clinical depression during the three years of study. One of the researchers, Prof Ian Goodyer, said: "Depression is a terrible illness that will affect as many as 10 million people in the UK at some point in their lives. "Through our research, we now have a very real way of identifying those teenage boys most likely to develop clinical depression. BBC © 2014

Keyword: Depression; Aggression
Link ID: 19261 - Posted: 02.18.2014

Ian Sample, science correspondent, in Chicago Researchers have found evidence – if evidence were needed – that men have less sex after becoming a father for the first time. A study of more than 400 young men in the Philippines found that their sex lives declined significantly when they had their first child. The fall in sexual activity was associated with the men's testosterone levels, which are known to fall when men start families, but the latest research shows that the greater the fall in testosterone, the less sex men reported. Lee Gettler, an anthropologist at the University of Notre Dame in Indiana, gathered medical and lifestyle information on the men from the ages of 21 to 26 years old and found there were physiological and behavioural changes as some of them married and had children. When men got married their testosterone levels fell, and declined even further when they had their first child. That led to the question of whether falling testosterone might impact on their sex lives. "I didn't think that testosterone would be linked to men's sexual behaviour, but when we tested it we found that as men transitioned to fatherhood, the more their testosterone declined the less frequently they reported having sex with their partner," Gettler said. "Does this mean that men who care for children have low testosterone and no sex? No, it has nothing to do with childcare." The impact on men's sex lives was not linked to the amount of time and energy they invested in childcare, he said. Gettler described his research at the annual meeting of the American Association for the Advancement of Science in Chicago. © 2014 Guardian News and Media Limited

Keyword: Hormones & Behavior; Aggression
Link ID: 19250 - Posted: 02.15.2014

By SINDYA N. BHANOO Mosquito sperm have a sense of smell, researchers are reporting, in a finding that could suggest ways to help control the spread of disease-carrying insects. The sperm carries a set of chemical sensors identical to the olfactory receptors on the mosquitoes’ antennas, according to a study in Proceedings of the National Academy of Sciences. Mosquitoes mate just once in their lifetime, and the female stores the male’s sperm in an organ called a spermatheca. Before the eggs mature, the female seeks out blood using the receptors on her antennas. Soon after, chemical signals cause the sperm tails to beat rapidly and start the fertilization process. “The sperm may need a chemical signal to become ready for fertilization,” said Jason Pitts, a researcher at Vanderbilt University and an author of the study, which was supported by the Gates Foundation as part of its efforts to improve global health. Another author, Laurence Zwiebel, also a Vanderbilt researcher, called the dual use of the olfactory receptors a clear and clever example of convergent evolution: The mosquitoes, he said, “found something that works and use it in multiple ways.” The scientists think olfactory receptors may exist on the sperm of many other insects, and they are developing chemical compounds that can be applied to breeding grounds to block the receptors. “You can effectively confuse the sperm or make them inactive,” Dr. Zwiebel said. © 2014 The New York Times Company

Keyword: Chemical Senses (Smell & Taste); Aggression
Link ID: 19241 - Posted: 02.12.2014

By JOHN LA PUMA SANTA BARBARA, Calif. — A FUNNY thing has happened in the United States over the last few decades. Men’s average testosterone levels have been dropping by at least 1 percent a year, according to a 2006 study in The Journal of Clinical Endocrinology and Metabolism. Testosterone appears to decline naturally with aging, but internal belly fat depresses the hormone further, especially in obese men. Drugs like steroids and opiates also lower testosterone, and it’s suspected that chemicals like bisphenol A (or BPA, commonly found in plastic food containers) and diseases like Type 2 diabetes play a role as well. Men feel the loss. Clinical testosterone deficiency, which is variously defined as lower than 220 to 350 nanograms of testosterone per deciliter of blood serum, can cause men to lose sex drive and fertility. Their bone density often declines, and they may feel tired and experience hot flashes and sweats. But “low T,” as the condition has been labeled, isn’t nearly as common as the drug ads for prescription testosterone would have you believe. Pharmaceutical companies have seized on the decline in testosterone levels as pathological and applicable to every man. They aim to convince men that common effects of aging like slowing down a bit and feeling less sexual actually constitute a new disease, and that they need a prescription to cure it. This is a seductive message for many men, who just want to feel better than they do, and want to give it a shot, literally. The problem is that prescription testosterone doesn’t just give your T level a boost: it may also increase your risk of heart attack. It can add huge numbers of red blood cells to your bloodstream and shrink your testes. In some men, it increases aggression and irritability. © 2014 The New York Times Company

Keyword: Hormones & Behavior
Link ID: 19238 - Posted: 02.11.2014

by Laura Sanders A new analysis of cows shows that mamas make more milk for daughters. Other studies have hinted that human moms produce different milk for sons than for daughters, so perhaps lactating women also boost production for daughters. I love eavesdropping on people’s overly detailed coffee orders. You, sir, with the temerity to order a skinny split quad shot latte no whip no foam, with a side of lemon? Your extreme customizing just made my day. Such personalization was running through my mind as I read a recent study on cows. It turns out that another beverage is also subject to the specific, exacting standards of its drinker: milk. And the customer’s bossy demands seem to start before he or she is born. Heifers produce more milk for daughters than sons, Katie Hinde and colleagues report February 3 in PLOS ONE. When a cow gives birth to her first female, she makes about 1.6 percent more milk than she would have for a son, Hinde and colleagues found by analyzing the dairy records from a million and a half cows. And because calves born at dairy farms are taken away from their mothers soon after birth, the female calves’ requests to “make me more milk” must have come during pregnancy. Another interesting finding: The first pregnancy had an outsized effect on the cow’s future milk production. Cows that had sons first saw a slight bump in production when they got pregnant with a daughter, but didn’t catch up to the cows that had a daughter followed by a son. The first born daughter set the mom’s milk-making machinery on high, and that’s where it stayed for subsequent pregnancies. © Society for Science & the Public 2000 - 2013

Keyword: Sexual Behavior
Link ID: 19237 - Posted: 02.11.2014

You probably saw dozens of people’s faces today, many more if you live in a city. You may not have been conscious of it, but you were subtly judging every one by its beauty. Your eyes are drawn to more attractive faces, and the almost inescapable result is that more attractive people have advantages in almost every aspect of life, from job interviews to prison sentencing. But what drives us to crave beauty? According to one theory, gazing upon beauty stimulates the brain’s μ-opioid receptors (MOR), thought to be a key part of our biochemical reward system. At least in rodents, stimulating or inhibiting MOR neurotransmission not only tweaks the animals’ appetite for sex or food, but also the strength of their preferences for particular foods or mates. Is our preference for pretty faces driven by the same biochemical reward circuit? To find out, researchers invited 30 heterosexual men to browse a series of female faces on a computer (one pictured). Each man received either a dose of the MOR-stimulating drug morphine, the opioid receptor–inhibiting drug naltrexone, or a placebo. The results, published today in Molecular Psychiatry, suggest that we seek out beautiful faces at least in part because our brains reward us. Not only did stimulating MOR neurotransmission cause men to linger longer on faces that they rated as more beautiful, but the beauty rating also became more extreme, with beautiful faces rated as even more attractive relative to the rest of the faces. Inhibiting MOR had the opposite effects. The findings are yet more evidence that our social interactions are strongly influenced by the invisible hand of evolution, pushing us to find attractive mates. But the question remains, how do we decide which face is attractive in the first place? © 2014 American Association for the Advancement of Science

Keyword: Sexual Behavior; Aggression
Link ID: 19232 - Posted: 02.11.2014

Women have a poorer quality of life after a stroke than men, a study has found. The US research, published in Neurology, assessed the mental and physical health of 1,370 patients three months and a year after a stroke. Women had more depression and anxiety, pain and discomfort, and more restricted mobility. UK experts said women tended to have strokes later, and might therefore need more support. But the study did say more people survive a stroke now than 10 years ago because of improved treatment and prevention. The researchers at Wake Forest Baptist Medical Center, North Carolina, looked at patients who had had a stroke or transient ischaemic attack (TIA), also known as a mini-stroke. Quality of life is calculated using a formula that assesses mobility, self-care, everyday activities, depression/anxiety and pain. At three months, women were more likely than men to report problems with mobility, pain and discomfort, anxiety and depression, but the difference was greatest in those aged over 75. After a year, women still had lower quality-of-life scores overall than men but the difference between them was smaller. Support needs Prof Cheryl Bushnell, who led the study, said: "We found that women had a worse quality of life than men up to 12 months following a stroke." BBC © 2014

Keyword: Stroke; Aggression
Link ID: 19221 - Posted: 02.08.2014

By Matt McGrath Environment correspondent, BBC News Successful professional cyclists are seen as more handsome than their struggling colleagues, according to new research. Women rated facial attractiveness among riders in the 2012 Tour de France, won by Britain's Sir Bradley Wiggins. The top 10% of performers were rated on average as 25% better looking than the laggards. The scientists conclude that humans have evolved to recognise athletic performance in faces. The research has been published in the Royal Society journal, Biology Letters. Some biologists argue that evolution has shaped women to select mates on the basis that they would either make good fathers or would pass on good genes. Healthy, physically fit men would on average be seen as more attractive by women. A number of other studies in recent years have suggested that women have a sophisticated radar for athletic performance, rating those with greater sporting skill as more attractive. This new work, though, set out to test if the same applied to more inherent physical qualities such as stamina and endurance. Cycle of life Dr Erik Postma, from the Institute of Evolutionary Biology at the University of Zurich, asked people to rate the attractiveness of 80 professional cyclists from the 2012 Tour de France. The cyclists were all of a similar physical stature, were tanned and around the same age. BBC © 2014

Keyword: Sexual Behavior; Aggression
Link ID: 19214 - Posted: 02.06.2014

By RONI CARYN RABIN Nearly a decade ago, researchers in Boston decided to see whether older men who were not in very good shape could benefit from daily doses of testosterone. The scientists recruited several hundred volunteers and gave them the hormone or a placebo. Those taking testosterone got stronger, compared with those taking the placebo, and they could carry a load up stairs faster. But they also had nearly five times the number of cardiovascular problems, including heart attacks and strokes, and safety monitors ended the trial early. Since those findings were published in 2010, studies of testosterone treatment have produced mixed results. A 2012 study of veterans aged 40 and over with low testosterone found that those treated with the hormone were less likely to die, but more recent reports, including one published last week, have documented an increase in cardiovascular risk in men over age 65 taking testosterone, as well as in younger men with a history of heart disease. Officials at the Food and Drug Administration said on Friday that they were reassessing the safety of testosterone products in light of the recent studies, and will investigate rates of stroke, heart attack and death in men using the drugs. In recent years, testosterone has been heavily promoted as a cure-all for low energy, low libido, depression and other ills among middle-aged men. “Low T” is a ubiquitous diagnosis, heard in television commercials and locker rooms. Between 2001 and 2011, hormone use by men 40 and over nearly quadrupled. By the end of that period, nearly one in 25 men in their 60s was taking testosterone. Though the drug is indicated for men with abnormally low testosterone levels, a condition called hypogonadism, doctors have been prescribing it to many men with normal levels. © 2014 The New York Times Company

Keyword: Hormones & Behavior; Aggression
Link ID: 19199 - Posted: 02.04.2014

Controversy delights Dick Swaab; brains delight him; complexity delights him, though I don't know if you'd get that from reading his book, We Are Our Brains, in which causal links are made quite casually, like a man doing a crossword with a pencil. The Dutch neurologist is, after a 50-year career, a giant in the field. He is a professor of neurobiology at the University of Amsterdam. His directorship of the Dutch Institute for Brain Research yielded material that has been sent to 500 other research groups in 25 countries. He has propounded groundbreaking theories in his specialist area: the impact on brain development in the womb. Nonetheless, his book, despite directing itself squarely to the layperson, has been miles more successful than he thought, selling 100,000 copies ("the publishers say they knew it would be a hit. But at the start, they only printed 3,000 copies. So I know that is not true."). There are a number of lines you might file under, "Well, there's a curiosity" (for instance: "In professional violinists, the part of the cerebral cortex that directs the fingers of the left hand is five times as large as it is in people who don't play a stringed instrument"). And yet the real fireworks of the book are both more predictable and more profound: Swaab says hormones and chemical substances in utero affect the development of our sexual orientation or, put more simply, you have a gay brain by the time you are born. Male and female brains have "hundreds of differences", which explain all the ways in which men and women are different; "phobia, impulsiveness, ADHD and depression later in life" can be traced back to a mother's fearfulness during pregnancy, which activates her baby's "fear axis". © 2014 Guardian News

Keyword: Sexual Behavior
Link ID: 19189 - Posted: 01.30.2014

Parasites don’t just cause nasty infections; they can also take over the minds of their hosts. The Ophiocordyceps fungus, for example, forces ants to climb up the stems of plants, where they die and release the fungus’s spores into the air to infect more ants. Likewise, it would make sense for sexually transmitted parasites to force their hosts to have sex more. But biologists have found very few examples of this in nature. A new study may explain why. To figure out why there isn’t more “sexual mind control” in nature, theoretical ecologist Ludek Berec, of the Biology Centre of the Academy of Sciences of the Czech Republic, and biological mathematician Daniel Maxin, of Valparaiso University in Indiana, turned to mathematical modeling. They created two strains of a hypothetical parasite species: an “ancestor” that did not make its hosts have sex more, and a mutant that did. Then they turned the two strains loose in a hypothetical host population and watched the parasites compete until the mutant strain either died out or replaced its ancestor. If the mutant strain replaced its ancestor, the researchers introduced a new mutant that had even more power over its host’s sex life. They then watched the two strains compete again, introduced yet another, stronger mutant when the old one outcompeted its predecessor, and so on. In this way, the species as a whole could “evolve” to exert more or less sexual mind control over its host. © 2014 American Association for the Advancement of Science.

Keyword: Sexual Behavior
Link ID: 19180 - Posted: 01.29.2014

By SINDYA N. BHANOO In pursuit of a mate, male fruit flies often engage in combat, battling one another with their front legs. But when the flies are brothers, they are more likely to cooperate, researchers are reporting. In a new study in the journal Nature, Tommaso Pizzari, a zoologist at the University of Oxford, and colleagues write that brother flies live longer as a result. And there are clear benefits for females who live among brothers: They have a longer reproductive life span, a faster rate of egg production and a greater chance of laying eggs that mature to adulthood. The researchers exposed female flies in a laboratory to several different sets of males — three brothers; two brothers and an unrelated male; and three unrelated males. The most peaceful groups were the ones with three brothers, perhaps because supporting one’s kin is an alternative way to pass on common genes. “You can improve your reproductive success yourself or help individuals who also share your genes,” Dr. Pizzari said. Although fruit flies have been extensively studied in labs, the structure of their natural societies remain a bit of a mystery. © 2014 The New York Times Compan

Keyword: Sexual Behavior; Aggression
Link ID: 19168 - Posted: 01.25.2014

by Erika Engelhaupt Twerking is so 50 million years ago. In fact, it’s probably much older than that. Today, the provocative, butt-shaking dance move is enough of a social phenomenon to merit a word in the dictionary (with twerking defined about as tastefully as possible here by actor Morgan Freeman), but animals have been shaking their hindquarters for ages, for a variety of purposes (more on that below). Black widow spiders are the latest documented twerkers. In their case, it’s the males that shake their rears. Black widow females are aggressive predators and will immediately kill any prey detected in their webs. This presents a problem for males approaching a female to mate; in this case a literal misstep means becoming the female’s dinner. To figure out how the males avoid being eaten (at least before mating), researchers at Simon Fraser University in Canada measured vibrations created by males and by prey in webs of western black widows (Latrodectus hesperus). They compared the vibrations, and the females’ responses, to those of the hobo spider (Tegenaria agrestis), a species in which females rarely attack courting males. To capture the details of small vibrations, they used a fun tool called a laser Doppler vibrometer, which measures small changes in a laser beam aimed at a surface. Sure enough, black widow males appeared to have a death-avoidance strategy. They produced vibrations different from thrashing prey by means of “lengthy andrepeated bouts of abdominal tremulations” averaging 43 wiggles per second, the researchers report January 17 in Frontiers in Zoology. You can see a male's moves in this video: © Society for Science & the Public 2000 - 2014

Keyword: Sexual Behavior; Aggression
Link ID: 19167 - Posted: 01.25.2014