Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases
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Roger Dobson Love, according to romantics, can have a dramatic effect on the senses: striking lovers blind, deaf or rendering them tongue-tied. But the simple answer to the question of whether any relationship is "the one" seems to be that your ideal man or woman gets up your nose. New research suggests a sense of smell is vital for a good long-term relationship. In the new study, reported in the journal Biological Psychology, researchers looked for the first time at the effect of being born without a sense on smell on men and women's relationships. The research involved analysing data on men and women aged 18 to 46 with no sense of smell and comparing it with information gleaned from a healthy control group. The results showed that men and women who were unable to smell had higher levels of social insecurity, although this manifested itself in different ways. In men, but not in women, it led to fewer relationships. The men with a faulty sense of smell averaged two partners compared with 10 for healthy men. One theory is that the lack of a sense of smell may make men less adventurous. They may have more problems assessing and communicating with other people. They may also be concerned about how they are perceived by others, and worry about their own body odour. © independent.co.uk
By Kate Shaw Early one morning I caught sight of Morpheus, silhouetted against a pink African dawn. Her long, sloping neck was stretched out as she loped away from me, disappearing over a hill. I followed her to a nearby plain and was met with the unmistakable sound of a group of hyenas squabbling over a carcass. Morpheus entered the fray, first lunging at a smaller male on her right. A moment later, she looked up briefly, her nose and mouth covered in blood, then turned and snapped at a hyena feeding nearby. I’m intimately acquainted with Morpheus and these other hyenas because they have been studied for more than twenty years by various members of the lab where I did my Ph.D. research; I’ve staked these hyenas out at dens for hours on end and followed them as they raced across open plains. From watching these animals, we’ve learned about hyenas’ social system, their physiology, and the conservation challenges they face. But to me, it’s the aggression that is the most fascinating thing about hyenas. It’s rule-based and constrained by specific social norms, but at the same time, it’s incredibly primal and ruthless. Studying aggression has helped us understand what makes hyenas tick, offering us a glimpse into the evolutionary pressures that have made them one of the most unusual and misunderstood species in the animal kingdom. For more than 1000 years, people believed that hyenas were hermaphrodites, since female hyenas have long, fully-erectile pseudopenises that mimic male genitalia. Seeing a hyena play the role of mom while sporting what looks like a penis would bewilder even an astute naturalist. Not only do female hyenas look like males, they are also the more aggressive and socially dominant sex, exhibiting aggression more than three times more often than male hyenas do. © 2012 Scientific American
By David P. Barash Critics claim that evolutionary biology is, at best, guesswork. The reality is otherwise. Evolutionists have nailed down how an enormous number of previously unexplained phenomena—in anatomy, physiology, embryology, behavior—have evolved. There are still mysteries, however, and one of the most prominent is the origins of homosexuality. The mystery is simple enough. Its solution, however, has thus far eluded our best scientific minds. The sine qua non for any trait to have evolved is for it to correlate positively with reproductive success, or, more precisely, with success in projecting genes relevant to that trait into the future. So, if homosexuality is in any sense a product of evolution—and it clearly is, for reasons to be explained—then genetic factors associated with same-sex preference must enjoy some sort of reproductive advantage. The problem should be obvious: If homosexuals reproduce less than heterosexuals—and they do—then why has natural selection not operated against it? The paradox of homosexuality is especially pronounced for individuals whose homosexual preference is exclusive; that is, who have no inclination toward heterosexuality. But the mystery persists even for those who are bisexual, since it is mathematically provable that even a tiny difference in reproductive outcome can drive substantial evolutionary change. Copyright 2012.
By Scicurious Last week, Sci covered a paper on the nematode “version” of oxytocin, nematocin, and its role in learning behavior. We usually think of oxytocin-like peptides (including oxytocin and vasopressin), as being linked with emotion, trust, love, and of course, sex. But oxytocin also tends to get a lot of hype, especially as the “love”‘ or “trust” hormone. But it’s not that. It’s much more complicated than that. And understanding the evolution of oxytocin, and its very long history, allows us to understand HOW much more complicated than that. Because while nematodes have an oxytocin-like molecule that has roles in learning behavior…well it also has roles in mating. But I wouldn’t go do far as to call nematocin (oxytocin + nematode = nematocin!) the nematode love drug. Unless, of course, you believe nematodes have deep, passionate, trusting, and communicative one-night worm stands which commence upon immediate contact and end immediately after. Hey, you never know. This happens to be an interesting issue of Science, in which TWO papers were published, both identifying nematocin, at the same time. As they both call the new molecule nematocin, I have hopes that the two groups were happily collaborating with each other to further the interests of science (though I know that many times, when two groups find the name new, hot thing, it’s often a very bitter race to publish). So what is nematocin? Nematocin appears to be a chemical closely related to oxytocin and vasopressin, those much vaunted chemical in mammals which are making so much press for their role in our emotions and moral behavior. But oxytocin and vasopressin are both more complicated than emotion. Vasopressin, for example, plays a role in water balance. And it appears that the newly discovered nematocin in the nematode C. elegans may be similar, with more than one role in more than one system. © 2012 Scientific American
Richard A. Lovett Scientists have known for years that human medications, from anti-inflammatories to the hormones in birth-control pills, are ending up in waterways and affecting fish and other aquatic organisms. But researchers are only beginning to compile the many effects that those drugs seem to be having. And it isn't good news for the fish. One such drug, fluoxetine, is the active ingredient in the antidepressant Prozac. Like some other pharmaceuticals, fluoxetine is excreted in the urine of people taking it, and reaches lakes and waterways through sewage-treatment plants that are unequipped to remove it. To investigate the effects of fluoxetine, researchers have turned to a common US freshwater fish species called the fathead minnow (Pimephales promelas). Normally, fathead minnows show a complex mating behaviour, with males building the nests that females visit to lay their eggs. Once the eggs are laid and fertilized, the males tend to them by cleaning away any fungus or dead eggs. But when fluoxetine is added to the water, all of this changes, said Rebecca Klaper, an ecologist at the University of Wisconsin-Milwaukee's Great Lakes Water Institute. Klaper presented her results this week at the 2012 meeting of the North American division of the Society of Environmental Toxicology and Chemistry in Long Beach, California. © 2012 Nature Publishing Group,
By Melissa Healy, Los Angeles Times If retired Army Gen. David H. Petraeus had gotten an occasional dose of supplemental oxytocin, a brain chemical known to promote trust and bonding, he might still be director of the Central Intelligence Agency, new research suggests. A study published Tuesday in the Journal of Neuroscience has uncovered a surprising new property of oxytocin, finding that when men in monogamous relationships got a sniff of the stuff, they subsequently put a little extra space between themselves and an attractive woman they'd just met. Oxytocin didn't have the same effect on single heterosexual men, who comfortably parked themselves between 21 and 24 inches from the comely female stranger. The men who declared themselves in "stable, monogamous" relationships and got a dose of the hormone chose to stand, on average, about 6 1/2 inches farther away. When researchers conducted the experiment with a placebo, they found no differences in the distance that attached and unattached men maintained from a woman they had just met. Even when an attractive woman was portrayed only in a photograph, the monogamous men who received oxytocin put a bit more distance between themselves and her likeness. But when the new acquaintance was a man, administration of oxytocin did not prompt attached men to stand farther away than single men, the researchers reported. Los Angeles Times, Copyright 2012
by Andy Coghlan Men with partners increase the space they feel comfortable with between themselves and an attractive woman if exposed to the bonding hormone oxytocin. René Hurlemann at the University of Bonn in Germany and colleagues gave men either a sniff of oxytocin or a placebo before asking them to choose the ideal distance for an interaction with a woman. The distance that they felt was comfortable significantly increased after sniffing oxytocin, but only for men in relationships. The team conclude that oxytocin discourages partnered but not single men from getting close to a female stranger. Journal reference: Journal of Neuroscience, DOI: 10.1523/jneurosci.2755-12.2012 © Copyright Reed Business Information Ltd.
By SINDYA N. BHANOO Fairywrens teach their chicks a password, a unique note, to differentiate them from imposters. “We call this an incubation call,” said Mark Hauber, an animal behaviorist at Hunter College at the City University of New York and an author of the study, which appears in the journal Current Biology. “The more times the mother calls, the better the mimicry of the chicks.” The teaching begins a few days before the birds hatch. And while “the cuckoo chick is very adaptable and tries out many begging calls until it sounds similar to the fairywren,” Dr. Hauber said, it also has a shorter incubation period. So it hatches several days before fairywren chicks, leaving it little time to practice and perfect the passwordlike call of the fairywren mother. Generally, when a cuckoo hatches it throws out the other eggs in the nest. When a mother does not hear her unique call from her babies, she abandons the nest. Male fairywrens help their mates care for their young, so the mother teaches her mate and any other helpers the password through the performance of a special song. “In the future we’d like to do some brain imaging on the embryos using noninvasive functional M.R.I.’s,” Dr. Hauber said. “We want to see how these embryos are listening, practicing and learning these relevant vocalizations.” © 2012 The New York Times Company
By Laura Sanders The effects of a baby’s rough start can linger. An early stressful environment during a baby girl’s first year was associated with altered brain behavior and signs of anxiety in her late teens, scientists report online November 11 in Nature Neuroscience. Although the results are preliminary, they may help reveal how negative experiences early on can sculpt the brain. Studies in animals have pointed out how tough times in childhood can influence the brain and the animals’ behavior later in life. But it’s been hard to figure out how that process works in people, says Lawrence Price, a psychiatrist and clinical neuroscientist at Brown University in Providence, R.I. “One of the real advances of this paper is that it helps move us along on that pathway,” he says. The study, led by Cory Burghy of the University of Wisconsin–Madison, drew from the Wisconsin Study of Family and Work, which in 1990 recruited pregnant women in southern Wisconsin at prenatal visits. Three times during the first year of their babies’ lives, the mothers reported whether they were experiencing stressful situations such as depression, marital conflict, money woes or parenting stress. Researchers assumed that women who reported higher stress levels created a more stressful situation for their baby. Four and a half years later, daughters whose moms reported higher levels of stress had more of the stress hormone cortisol in their blood. That observation suggests the girls had trouble shutting down a hyperactive stress response. The same effect wasn’t found in boys. © Society for Science & the Public 2000 - 2012
By Laura Sanders In the fraught, emotional world of speed dating, scientific calculations don’t usually hold much sway. But the brain runs a complex series of computations to tally the allure of a prospective partner in just seconds, a new study finds. And the strength of these brain signals predicted which speed daters would go on to score a match. The results help explain how people evaluate others — a process that happens at lightning speed, says neuroscientist Daniela Schiller of Mount Sinai School of Medicine in New York City. “It’s a gut feeling, but here, the paper dissects it for us and tells us, ‘This is what we calculate.’” Scientists led by Jeffrey Cooper, who conducted the work at Trinity College Dublin and Caltech, scanned the brains of single volunteers as they looked at pictures of potential dating partners. Although it’s hard to put a number on people by a photo alone, researchers made volunteers rate on a scale of 1 to 4 how much they’d like to go on a date with the person in the photograph. In contrast to many other lab-based experiments on decision making, this exercise wasn’t just academic: Later, the participants attended three real speed-dating events loaded with many of the potential partners seen in the photos. Like a normal speed-dating scenario, volunteers’ contact information was exchanged if both of the people wanted to follow up. (Also like a typical scenario, there weren’t many love connections, says Cooper. When the scientists checked in six weeks later, only a few couples had gone on real dates.) © Society for Science & the Public 2000 - 2012
By Caroline Parkinson Health editor, BBC News website The brains of teenage girls with behavioural disorders are different to those of their peers, UK researchers have found. The Journal of Child Psychology and Psychiatry study of 40 girls revealed differences in the structure of areas linked to empathy and emotions. Previous work has found similar results in boys. Experts suggest it may be possible to use scans to spot problems early, then offer social or psychological help. An estimated five in every 100 teenagers in the UK are classed as having a conduct disorder. It is a psychiatric condition which leads people to behave in aggressive and anti-social ways, and which can increase the risk of mental and physical health problems in adulthood. Rates have risen significantly among adolescent girls in recent years, while levels in males have remained about the same. In this study, funded by the Wellcome Trust and Medical Research Council, UK and Italian researchers conducted brain scans of 22 teenage girls who had conduct disorder and compared them with scans of 20 who did not. BBC © 2012
By Marcia Malory Ask this question, and you will probably receive one of two responses: Yes. People choose to be gay. They are making an immoral choice, which government should discourage. Or No. Sexual preference is biologically determined. Government should protect gay people from discrimination because homosexuality is an unalterable aspect of their identity. These two answers have something in common: With both of them, the science conveniently supports the moral decision. What if neither answer is right? Perhaps sexual preference can be changed – and people have the right to engage in gay sex and have homosexual relationships if they choose to do so. (The fourth option, that gay people have no choice but to be gay, but should be punished for it anyway, is morally unthinkable.) What does science tell us about sexual preference? We know, from many twin and adoption studies, that sexual preference has a genetic component. A gay man is more likely than a straight man to have a (biological) gay brother; lesbians are more likely than straight women to have gay sisters. In 1993, a study published in the journal Science showed that families with two homosexual brothers were very likely to have certain genetic markers on a region of the X chromosome known as Xq28. This led to media headlines about the possibility of the existence of a “gay gene” and discussions about the ethics of aborting a “gay” fetus. © 2012 Scientific American,
By Ferris Jabr With the exception of the cast of Disney’s The Little Mermaid—and Big Mouth Billy Bass—fish do not spring to mind as the animal kingdom’s most vocally gifted members. But one unusual singing fish has been teaching biologists and neuroscientists a lot about speech and hearing. Its bulging eyes and blubbery lips have graced several research posters at the Society for Neuroscience’s annual meeting, which is in New Orleans, Louisiana this year. The finned crooner in question is the plainfin midshipman fish (Porichthys notatus), which belongs to a family of fish known as toadfish because of their squat, slimy appearance. Midshipman fish live along the Pacific coast from Alaska to Baja California at depths of up to 300 meters, burying themselves in the mud during the day and surfacing at night to feed. Their name is attributable to the hundreds of luminous spots called photophores that decorate their underbellies, which are somewhat reminiscent of the buttons on a naval officer’s uniform. The fish likely use these bioluminescent dots to attract small prey such as krill and to hide from predators by masking their own shadows with a camouflage technique known as counter-illumination. Midshipman fish come in three varieties: females, Type I males and the smaller Type II males. All three types are vocal, emitting short grunts to communicate with one another, but Type 1 males are the most voluble by far. In the spring and summer, Type 1 males head to shallow waters, excavate nests beneath rocks along the shoreline, hunker down and start to sing, using sonic muscles surrounding their inflatable swim bladders to hum for up to an hour at a time. This humming, which people have described a droning motorboat or an orchestra of mournful oboes, is so loud that it has been known to wake houseboat owners in San Francisco and Sausalito © 2012 Scientific American,
By Gary Stix First off, this study on a molecule tied to social interaction was conducted in animals. So I’m supposed to turn on the siren and the flashing red light here to let you know that the headline you just read might not apply in humans. Still, the animals in question, prairie voles, are a special case, models of faithfulness that put humans to shame when it comes to the delicate topic of monogamy. Once hitched, the rodents stick with their mates for life—an example of moral pulchritude in the animal kingdom that many of us human sinners can never hope to emulate. It could easily become the state animal for whole regions of the U.S. For just that alone, the implications of the experiment in question are particularly intriguing. The new research shows that oxytocin, the bonding hormone, is sometimes capable of turning the upstanding rodent into an anti-social lout, making the study results more compelling in many ways than if they were reported in errant humans. So the man-bites-dog headline stays. This all came up when Karen Bales, a professor at University of California, Davis, wanted to know what would happen if oxytocin gets administered for lengthy intervals, not the short-term dosing that has occurred in the multitude of previous vole studies that linked the hormone to monogamous behavior. In their experiment, Bales and team gave either a low, medium or high dose through the nose to 29 voles, and a saline solution to 14 controls At first, the animals became all cuddly as in previous studies But after three weeks, an entire vole childhood (from weaning to sexual maturity), they started breaking bad. Males did not engage in the normal behavior of “pair bonding,” that drives them to look for the girl of their dreams. And female voles’ natural mothering instinct seemed to disappear: when placed nearby young pups that were not their own, they didn’t dote, as they are wont to do. The cuddle hormone had turned the rodents into meanies. © 2012 Scientific American
(Relaxnews)—In a study of more than 90 men, scientists from the University of Bonn, Germany, found that subjects treated with a dose of testosterone before the study told fewer lies than those who received a placebo. "Testosterone has always been said to promote aggressive and risky behavior and posturing," says researcher and neuroscientist Bernard Weber. However, more recent studies indicate that it also fosters social behavior. Prior research has suggested that the hormone may actually cause people to be more "prosocial" in that they voluntarily act in the interest of others, writes the Atlantic magazine, but exactly how the hormone influences behaviors isn't understood. For this latest study, 46 subjects were treated with testosterone by applying it to the skin in gel form, while 45 subjects received a placebo. The next day, the subjects played a dice game in which it was easy for the men to lie to earn more money, with no possibility of being caught. The study was designed so that it was impossible even for the researchers to detect whether a subject was lying or not. Rather, they used statistics to analyze reported earnings that were higher than probability would allow, inferring from these how honest the subjects were being. While many people in the study lied about the game, there was a noticeable difference between the men boosted with testosterone and those who weren't—the testosterone group avoided the temptation to cheat more often. Blood tests confirmed the results that high testosterone levels were linked with more honest game playing. "Test subjects with the higher testosterone levels had clearly lied less frequently than untreated test subjects," says co-author Armin Falk. "This result clearly contradicts the one-dimensional approach that testosterone results in anti-social behavior." The study was published last week in the journal PLoS One . http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0046774 © 2012 NY Times Co.
Keyword: Hormones & Behavior
Link ID: 17378 - Posted: 10.17.2012
By Jason G. Goldman My high school biology teacher once told me that nothing was binary in biology except for alive and dead, and pregnant and not pregnant. Any other variation, he said, existed along a continuum. Whether or not the claim is technically accurate, it serves to illustrate an important feature of biological life. That is, very little in the biological world falls neatly into categories. A new finding, published today in PLoS ONE by Gustavo Arriaga, Eric P. Zhou, and Erich D. Jarvis from Duke University adds to the list of phenomena that scientists once thought were categorical but may, in fact, not be. The consensus among researchers was that, in general, animals divide neatly into two categories: singers and non-singers. The singers include songbirds, parrots, hummingbirds, humans, dolphins, whales, bats, elephants, sea lions and seals. What these species all have in common – and what distinguishes them from the non-singers of the animal world – is that they are vocal learners. That is, these species can change the composition of their sounds that emanate from the larynx (for mammals) or syrinx (for birds), both in terms of the acoustic qualities such as pitch, and in terms of syntax (the particular ordering of the parts of the song). It is perhaps not surprising that songbirds and parrots have been extremely useful as models for understanding human speech and language acquisition. When other animals, such as monkeys or non-human apes, produce vocalizations, they are always innate, usually reflexive, and never learned. But is the vocal learner/non-learner dichotomy truly reflective of biological reality? Maybe not. It turns out that mice make things more complicated. © 2012 Scientific American
By Scicurious Ok, I know it’s not Friday Weird Science time, but this paper is both interesting science AND somewhat odd. And who can’t use extra weird in their day, right? I know that Ed has already been here before me, but I can’t let this one go. I like studies on sleep, and I like studies on sex, and this has both! This paper is not actually about gettin’ laid. Though it IS about getting laid…but what it’s really about is the purpose of sleep. What is the purpose of sleep? After all, 8 hours a night (ish, for humans) is an awfully long time to spend unconscious and relatively defenseless. But almost all animals (all mammals and birds, definitely) that have more than a rudimentary brain do it. This leads us to think that it must really be an important thing to do. But why? There are several hypotheses as to why we need to sleep. The one I see most often is that our brains need that relatively inactive time (though there is still a lot of activity) to perform restorative processes and promote the best brain performance. But we don’t know, exactly, what the restorative processes are. We just know that animals and humans perform very badly on tasks when sleep deprived. But there is another hypothesis. This is the hypothesis that sleep is not really all that necessary for optimal performance. Instead, sleep is a way to preserve energy when it’s a better idea to be inactive. So, for example, humans might sleep at night because we’re at a disadvantage in the dark and would waste energy attempting activities. Support for this hypothesis comes from the fact that sleep needs vary massively across the animal kingdom. Some animals need 14 hours (see cats), while others need just 2-3. © 2012 Scientific American,
By Bruce Bower A new study suggests that present-day Europeans share more genes with now-extinct Neandertals than do living Africans, at least partly because of interbreeding that took place between 37,000 and 86,000 years ago. Cross-species mating occurred when Stone Age humans left Africa and encountered Neandertals, or possibly a close Neandertal relative, upon reaching the Middle East and Europe in the latter part of the Stone Age, says a team led by geneticist Sriram Sankararaman of Harvard Medical School. The new study, published online October 4 in PLOS Genetics, indicates that at least some interbreeding must have occurred between Homo sapiens and Neandertals, Sankararaman says. But it’s not yet possible to estimate how much of the Neandertal DNA found in modern humans comes from that interbreeding and how much derives from ancient African hominid populations ancestral to both groups. A separate analysis of gene variants in Neandertals and in people from different parts of the world also found signs of Stone Age interbreeding outside Africa. That study, published online April 18 in Molecular Biology and Evolution, was led by evolutionary geneticist Melinda Yang of the University of California, Berkeley. Results from Sankararaman and Yang’s groups “convincingly show that the finding of a higher proportion of Neandertal DNA in non-Africans compared to Africans can be best explained by gene flow from Neandertals into modern humans,” says evolutionary geneticist Johannes Krause of the University of Tübingen in Germany. © Society for Science & the Public 2000 - 2012
By Susan Milius A patch over a male Gouldian finch’s right eye works like beer goggles, though the bird doesn’t need booze to flirt unwisely. If limited to using his left eye when checking out possible mates, he risks making really stupid choices. Gouldian finches have caps of black, red or yellow feathers on their heads. In nature, the birds prefer to mate with partners with the same cap color. Yet black-headed males rendered temporarily left-eyed by a tiny removable eye patch flirted as readily with red-heads as with black-heads, says cognitive ecologist Jennifer Templeton of Knox College in Galesburg, Ill. That’s not smart because daughters typically fail to survive when Gouldian finches mate outside their cap color. Also the male himself “becomes less attractive,” Templeton says. When the bird’s right eye was covered, he sang, bowed and posed less during his attempts at courtship. Some left-eyed males didn’t manage to make up their minds at all, but “just hopped around randomly,” Templeton says. Moving the eye patch to the right eye, however, restored male Gouldian finches to their senses. Males then spent more time perching near same-cap-color females and flirting with them. “Beauty is in the right eye of the beholder,” Templeton and her colleagues conclude online October 3 in Biology Letters. Birds make fine subjects for comparing eye biases because many species’ eyes sit on opposite sides of their skulls with very different fields of view. A bird’s right eye connects to the left hemisphere of its brain, and the left eye to the right hemisphere. Unlike mammals, birds don’t have a high-speed connection between hemispheres. © Society for Science & the Public 2000 - 2012
By Jennifer Viegas Bats may have more in common with the fictional Batman than previously believed, since both successfully combine work with courting sexy potential mates -- a lot of them. A new study, published in the latest Proceedings of the Royal Society B, reveals that bat echolocation calls, primarily used for orientation and foraging, also contain information about sex, which helps the flying mammals to acquire and keep mates. The info is especially helpful to certain male bats with harems of adoring females that are actually huskier than the males. This holds true for the greater sac-winged bat (Saccopteryx bilineata), which was the focus of the study. Lead author Mirjam Knörnschild told Discovery News that "male S. bilineata court females whenever the opportunity arises. The social information in echolocation calls about the sex of the calling bat benefits listening harem males because they can distinguish between females and male rivals. It might also benefit calling females because they are greeted friendly." athletes Knörnschild, a researcher at the University of Ulm's Institute of Experimental Ecology, and her team analyzed greater sac-winged bat echolocation calls. The scientists discovered that the calls contain "pronounced vocal signatures encoding sex and individual identity." This can include species identity, age, sex, group affiliation, and other more specific information about the individual. © 2012 Discovery Communications, LLC.