Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases
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by Tim Wall Some feathered crooners may advertise their size to females by hitting the low notes. Ornithologists at the Max Planck Institute found that only bigger-bodied birds belt out the bass. The physical size of some birds may put a limit on the frequency of the birds’ songs, according to a study published in PLOS ONE. Since only a larger males hit lower notes, females may be able to use deeper voices as a reliable measure of a male’s size. Size matters to some songbird species, with females preferring larger males, so vocal limitations could affect some birds’ love lives. The songs of purple-crowned fairy-wrens, Malurus coronatus coronatus, hit a range of notes. However the study found that in some songs, larger body size related to lower-pitched singing ability. Further study will be needed to prove a relationship among body size, singing frequency and sexual success in fairy-wrens. The authors suggested that body size may be just one of many characteristics advertized by fairy-wrens songs. The authors also noted that low-frequency singing ability may have resulted from good health as the male fairy-wrens grew up. Better health may have allowed better development of singing structures in the birds’ anatomies. The same healthy conditions could have also resulted in larger size. So size and singing would be correlated, but not causally related. © 2013 Discovery Communications, LLC.
By Athena Andreadis Genes are subject to multiple layers of regulation. An early regulatory point is transcription. During this process, regulatory proteins bind to DNA regions (promoters and enhancers) that direct gene expression. These DNA/protein complexes attract the transcription apparatus, which docks next to the complex and proceeds linearly downstream, producing the heteronuclear (hn) RNA that is encoded by the gene linked to the promoter. The hnRNA is then spliced and either becomes structural/regulatory RNA or is translated into protein. Transcription factors are members of large clans that arose from ancestral genes that went through successive duplications and then diverged to fit specific niches. One such family of about fifty members is called FOX. Their DNA binding portion is shaped like a butterfly, which has given this particular motif the monikers of forkhead box or winged helix. The activities of the FOX proteins extend widely in time and region. One of the FOX family members is FOXP2, as notorious as Fox News – except for different reasons: FOXP2 has become entrenched in popular consciousness as “the language gene”. As is the case with all such folklore, there is some truth in this; but as is the case with everything in biology, reality is far more complex. FOXP2, the first gene found to “affect language” (more on this anon), was discovered in 2001 by several converging observations and techniques. The clincher was a large family (code name KE), some of whose members had severe articulation and grammatical deficits with no accompanying sensory or cognitive impairment. The inheritance is autosomal dominant: one copy of the mutated gene is sufficient to confer the trait. When the researchers definitively identified the FOXP2 gene, they found that the version of FOXP2 carried by the KE affected members has a single point mutation that alters an invariant residue in its forkhead domain, thereby influencing the protein’s binding to its DNA targets. © 2013 Scientific American
by Michael Balter Despite recent progress toward sexual equality, it's still a man's world in many ways. But numerous studies show that when it comes to language, girls start off with better skills than boys. Now, scientists studying a gene linked to the evolution of vocalizations and language have for the first time found clear sex differences in its activity in both rodents and humans, with the gene making more of its protein in girls. But some researchers caution against drawing too many conclusions about the gene's role in human and animal communication from this study. Back in 2001, the world of language research was rocked by the discovery that a gene called FOXP2 appeared to be essential for the production of speech. Researchers cautioned that FOXP2 is probably only one of many genes involved in human communication, but later discoveries seemed to underscore its importance. For example, the human version of the protein produced by the gene differs by two amino acids from that of chimpanzees, and seems to have undergone natural selection since the human and chimp lineages split between 5 million and 7 million years ago. (Neandertals were found to have the same version as Homo sapiens, fueling speculation that our evolutionary cousins also had language). In the years since, FOXP2 has been implicated in the vocalizations of other animals, including mice, singing birds, and even bats. During this same time period, a number of studies have confirmed past research suggesting that young girls learn language faster and earlier than boys, producing their first words and sentences sooner and accumulating larger vocabularies faster. But the reasons behind such findings are highly controversial because it is difficult to separate the effects of nature versus nurture, and the differences gradually disappear as children get older. © 2010 American Association for the Advancement of Science
By JANE E. BRODY The title of a recent report on smoking and health might well have paraphrased the popular ad campaign for Virginia Slims, introduced in 1968 by Philip Morris and aimed at young professional women: “You’ve come a long way, baby.” Today that slogan should include: “…toward a shorter life.” Ten years shorter, in fact. The new report is one of two rather shocking analyses of the hazards of smoking and the benefits of quitting published last month in The New England Journal of Medicine. The data show that “women who smoke like men die like men who smoke,” Dr. Steven A. Schroeder, a professor of health and health care at the University of California, San Francisco, wrote in an accompanying editorial. That was not always the case. Half a century ago, the risk of death from lung cancer among men who smoked was five times higher than that among women smokers. But by the first decade of this century, that risk had equalized: for both men and women who smoked, the risk of death from lung cancer was 25 times greater than for nonsmokers, Dr. Michael J. Thun of the American Cancer Society and his colleagues reported. Today, women who smoke are even more likely than men who smoke to die of lung cancer. According to a second study in the same journal, women smokers face a 17.8 times greater risk of dying of lung cancer than women who do not smoke; men who smoke are at 14.6 times greater risk to die of lung cancer than men who don’t. Women who smoke now face a risk of death from lung cancer that is 50 percent higher than the estimates reported in the 1980s, according to Dr. Prabhat Jha of the Center for Global Health Research in Toronto and his colleagues. After controlling for age, body weight, education level and alcohol use, the new analysis found something else: men and women who continue to smoke die on average 10 years sooner than those who never smoked. Copyright 2013 The New York Times Company
by Lizzie Wade When a male wasp decides it's time to settle down and start a family, he releases a chemical calling card in the form of pheromones, broadcasting his location, his availability, and, most importantly, his identity. Most other kinds of insects will either ignore his signal or be repelled by it, but female wasps of his own species will buzz over and get down to business. But how and why did different pheromone blends—and the species that prefer them—evolve in the first place? A new study offers a possible solution to this long-standing evolutionary mystery, suggesting that new sex pheromones may evolve through genetic mutation before potential mates develop the ability to detect them. Scientists have long been impressed by the perfect harmony of chemical communication among insects, especially when it comes to choosing mates by detecting and responding to the sex pheromones of only their own species. But scientists were puzzled by how such a delicate system evolved. If female wasps respond to only a specific blend of pheromones, males that produce even a subtly different blend shouldn't have much luck mating and passing on their mutant genes. It seemed that in order for males to evolve new pheromones, the female insects would need some preexisting adaptation that would cause them to prefer the new chemical blend. But how could they evolve a preference for something they had never encountered and should, logic suggests, find off-putting? In essence, the question is which came first, a new species or its sex pheromone? In order to answer this question, a team of researchers in Germany turned to the Nasonia vitripennis wasp, a species famous for its propensity to lay its parasitic eggs on doomed fly pupae. When the scientists analyzed the N. vitripennis male sex pheromone, they found it contained two important chemicals, which they call RS and RR. RS also turns up in the male sex pheromones of another species of wasp, N. giraulti, whereas RR appears to be unique. © 2010 American Association for the Advancement of Science.
By RAPHAEL SATTER, Associated Press LONDON (AP) — When it comes to mating, guppies treasure their ugly friends — because they look so good by comparison. An article published Wednesday by Britain's Royal Society says that male guppies prefer to associate with their drab-colored counterparts when females were around. "Males actively choose the social context that maximizes their relative attractiveness," the article said. Or, as lead author Clelia Gasparini put it, "If you are surrounded by ugly friends, you look better." Gasparini and her colleagues at Italy's University of Padua built their theory on a kind of guppy dating game. An aquarium was set up with one female in partition on either end. Guppy bachelorette No. 1 had two attractive, brightly-colored males placed on either side of her. Guppy bachelorette No. 2 was stuck with uglier, drab-colored fish. When a male guppy was put in the middle of the tank, and given the choice of which female to sidle up to, Bachelorette No. 2 was the more popular pick, with male guppies spending about 62 percent of their time hanging around her side of the aquarium. What's more, the researchers found that the time guppies spent with bachelorette No. 2 correlated with their unattractiveness. The uglier the guppy, the less likely it was that he would hang around the brightly colored fish placed next to bachelorette No. 1. © 2013 Hearst Communications Inc.
Keyword: Sexual Behavior
Link ID: 17798 - Posted: 02.13.2013
Matt Kaplan The astounding warning colours of the nudibranchs, a diverse group of sea slugs, are certainly enough to attract attention — but even they pale in comparison to the gripping news that one species of the soft-bodied molluscs has a habit of discarding its penis. Nudibranchs are hermaphrodites, meaning that they carry both male and female reproductive organs. Moreover, when they mate, they can perform the male role of donating sperm and the female role of receiving sperm at the same time. This process involves two penises and two vagina-like organs, and sperm transmission effectively happens simultaneously during the encounter. This is a relatively standard arrangement among nudibranchs, so the creatures' sexual organs might all be expected to look roughly the same. But the animals show incredible sex-organ diversity, and it was during an exploration of this diversity in the species Chromodoris reticulata that researchers made their jaw-dropping discovery. A Japanese team led by Ayami Sekizawa at Osaka City University and Yasuhiro Nakashima at Nihon University in Tokyo went scuba diving off the coast of Okinawa to collect the sea slugs. They then placed the creatures in aquaria in pairs. In some cases both members of a pair had been isolated from others for 24 hours; in other cases a recently-mated animal was placed with one that had been in isolation. © 2013 Nature Publishing Group,
Keyword: Sexual Behavior
Link ID: 17797 - Posted: 02.13.2013
By Luciana Gravotta If cupid had studied neuroscience, he’d know to aim his arrows at the brain rather than the heart. Recent research suggests that for love to last, it’s best he dip those arrows in oxytocin. Although scientists have long known that this hormone is essential for monogamous rodents to stay true to their mates, and that it makes humans more trusting toward one another, they are now finding that it is also crucial to how we form and maintain romantic relationships. A handful of new studies show that oxytocin makes us more sympathetic, supportive and open with our feelings—all necessary for couples to celebrate not just one Valentine’s Day, but many. These findings have led some researchers to investigate whether oxytocin can be used in couple therapy. The first bit of evidence that points to oxytocin as nature’s love glue comes from researchers who measured the hormone in couples. Psychology professor Ruth Feldman at Bar-Ilan University in Israel, spent years studying oxytocin’s role in the mother–child bond and recently decided to dive into the uncharted waters of romantic bonds by comparing oxytocin levels in new lovers and singles. “The increase in oxytocin during the period of falling in love was the highest that we ever found,” she says of a study she and her colleagues published in Psychoneuroendocrinology. New lovers had double the amount Feldman usually sees in pregnant women. Oxytocin was also correlated with the longevity of a relationship. Couples with the highest levels were the ones still together six months later. They were also more attuned to each other than the low-oxytocin couples when Feldman asked them to talk about a shared positive experience. © 2013 Scientific American,
Nearly 400 years after William Shakespeare asked, "What is love?," brain imaging studies are allowing scientists to give at least a partial answer. As our calendars get closer to Feb. 14, a day when passion is deeply associated with the heart, love will in fact be in the mind. A recent study shows love is a complex emotion triggered by 12 specific areas of the brain — the network of love. Love is in the mind, not in the heart © 1996-2013 The Washington Post
By Laura Sanders Immune cells that help heal injuries in the adult brain may have a second job early in life, a study in mice reveals. The brain crusaders unexpectedly moonlight as sculptors, shaping a region of the brain into a male-specific form. The cells, called microglia, are mobile garbage disposals that travel around the brain and gobble up damaged cells and infectious agents. But the new study, published in the Feb. 13 Journal of Neuroscience, emphasizes that these cells have diverse functions, says neuroscientist Jean Harry of the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., who was not involved in the work. Earlier results hinted that parts of the immune system have a role in building sex differences into the brain, so Kathryn Lenz and her colleagues at the University of Maryland, Baltimore decided to test whether microglia are pulling double duty. The team focused on the preoptic area of the mouse brain—“a place where you see a ton of sex differences,” Lenz says. Early in life, this brain area gets shaped by sex hormones including molecules called estradiol and prostaglandin E2, which work on the male mouse brain. In males, the preoptic area is larger, and the cells there have more elaborate shapes than in females. Scientists think those brain differences drive mating behaviors. Lenz and her colleagues found another difference in the preoptic area between males and females: Young males had about twice as many active microglia as females did. What’s more, a dose of estradiol or prostaglandin E2 in the first few days of life caused female animals to produce the male number of active microglia. © Society for Science & the Public 2000 - 2013
By Morgen Peck Co-sleeping, the practice of sharing a bed with your baby, has a controversial place in modern society. Proponents argue that it increases the parent-child bond, whereas detractors worry about safety. Now an anthropological study adds a new finding to the debate: fathers who sleep next to their babies tend to have significantly lower levels of testosterone than those who sleep in a different room. Lee Gettler, an anthropologist at the University of Notre Dame, compared Filipino men's testosterone levels before having a child and again four years later. Men who reported sleeping on the same surface as their child experienced a steep decline in nighttime testosterone levels not seen in men who slept in another room, according to the paper published in September 2012 in PLOS One. Studies on women have shown that mothers who sleep with their children pass in and out of sleep. The same disruptions in men could possibly decrease testosterone production, Gettler and his co-authors write. Previous work in the same population showed that fathers who fully throw themselves into caring for their children are more likely to have low testosterone, suggesting that hormonal fluctuations may support men in being good fathers. “Lower testosterone might orient men more toward the needs of the partner and children and away from risky behavior and competition with other males—which could conflict with investments in parenting,” Gettler says. © 2013 Scientific American
The offspring of promiscuous baboon males are more successful when they have contact with their father, scientists have found. A study by a team of European researchers has documented increased feeding success when foraging with adult male baboons. Paternity analyses allowed the scientists to determine whether the males were, in fact, the fathers. The findings are published in the journal Behavioural Ecology. Paternal care is uncommon in promiscuous mammals where it is not obvious which male actually is the father. Lead researcher, Dr Elise Huchard of the University of Cambridge's Department of Zoology, told BBC Nature: "Caring for offspring can be costly in terms of time and energy for the parents." She explained that parental care increases the chances of offspring survival, as well as improving an individual's survival and reproductive performance later on in life. "Paternal care is usually observed in species where paternity certainty is high, [such as] in monogamous species," according to Dr Huchard. So when research suggested that juveniles benefitted from paternal input in promiscuous baboon troops, Dr Huchard and colleagues decided to perform field research on two troops of chacma baboons (Papio ursinus) in Tsaobis Leopard Park, central Namibia. BBC © 2013
Keyword: Sexual Behavior
Link ID: 17731 - Posted: 01.29.2013
By RONI CARYN RABIN Most sleeping pills are designed to knock you out for eight hours. When the Food and Drug Administration was evaluating a new short-acting pill for people to take when they wake up in the middle of the night, agency scientists wanted to know how much of the drug would still be in users’ systems come morning. Blood tests uncovered a gender gap: Men metabolized the drug, Intermezzo, faster than women. Ultimately the F.D.A. approved a 3.5 milligram pill for men, and a 1.75 milligram pill for women. The active ingredient in Intermezzo, zolpidem, is used in many other sleeping aids, including Ambien. But it wasn’t until earlier this month that the F.D.A. reduced doses of Ambien for women by half. Sleeping pills are hardly the only medications that may have unexpected, even dangerous, effects in women. Studies have shown that women respond differently than men to many drugs, from aspirin to anesthesia. Researchers are only beginning to understand the scope of the issue, but many believe that as a result, women experience a disproportionate share of adverse, often more severe, side effects. “This is not just about Ambien — that’s just the tip of the iceberg,” said Dr. Janine Clayton, director for the Office of Research on Women’s Health at the National Institutes of Health. “There are a lot of sex differences for a lot of drugs, some of which are well known and some that are not well recognized.” Copyright 2013 The New York Times Company
Keyword: Sexual Behavior
Link ID: 17725 - Posted: 01.29.2013
By BENEDICT CAREY Susan Nolen-Hoeksema, a psychologist and writer whose work helped explain why women are twice as prone to depression as men and why such low moods can be so hard to shake, died on Jan. 2 in New Haven. She was 53. Her death followed heart surgery to correct a congenitally weak valve, said her husband, Richard Nolen-Hoeksema. Dr. Nolen-Hoeksema, a professor at Yale University, began studying depression in the 1980s, a time of great excitement in psychiatry and psychology. New drugs like Prozac were entering the market; novel talking therapies were proving effective, too, particularly cognitive behavior therapy, in which people learn to defuse upsetting thoughts by questioning their basis. Her studies, first in children and later in adults, exposed one of the most deceptively upsetting of these patterns: rumination, the natural instinct to dwell on the sources of problems rather than their possible solutions. Women were more prone to ruminate than men, the studies found, and in a landmark 1987 paper she argued that this difference accounted for the two-to-one ratio of depressed women to depressed men. She later linked rumination to a variety of mood and behavior problems, including anxiety, eating disorders and substance abuse. “The way I think she’d put it is that, when bad things happen, women brood — they’re cerebral, which can feed into the depression,” said Martin Seligman, a professor of psychology at the University of Pennsylvania, who oversaw her doctoral work. “Men are more inclined to act, to do something, plan, beat someone up, play basketball.” © 2013 The New York Times Company
By SABRINA TAVERNISE WASHINGTON — For two decades, millions of Americans have taken Ambien to help them sleep at night. But for years, the Food and Drug Administration has gotten complaints that people felt drowsy the morning after taking the medicine or its successors, and sometimes got into car accidents. On Thursday the agency said that women should be taking half as much, after laboratory studies and driving tests confirming the risks of drowsiness. The new recommendation applies to drugs containing the active ingredient zolpidem, by far the most widely used sleep aid. Using lower doses means less of the drug will remain in the blood in the morning hours, and will reduce the risk that people who use it will be impaired while driving. Sleeping pills have boomed in popularity with the increasingly frantic pace of modern American life. According to IMS, a health care information and technology company, about 60 million prescriptions were dispensed in 2011, up about 20 percent since 2006. About 40 million were for products containing zolpidem. The agency’s announcement was focused on women because they take longer to metabolize the drug than men. An estimated 10 percent to 15 percent of women will have a level of zolpidem in their blood that could impair driving eight hours after taking the pill, while only about 3 percent of men do, said Dr. Robert Temple, an official in the agency’s Center for Drug Evaluation and Research. © 2013 The New York Times Company
By Susan Milius Male European blackbirds monitored in a lab under simulated city lighting started secreting increased levels of testosterone and growing their sexual organs up to a month earlier in the spring than birds kept in country-style darkness, Davide Dominoni of the Max Planck Institute for Ornithology in Radolfzell, Germany, reported January 6 at the annual meeting of the Society for Integrative and Comparative Biology. Dominoni’s colleagues have found that, outside the lab, male blackbirds flying around Munich undergo this growth surge about three weeks earlier than counterparts in a forest just 40 kilometers out of town. Beginning in December 2010, the researchers exposed captive blackbirds to night light levels typical of urban settings. They estimated those levels by outfitting free-flying blackbirds with light-sensitive devices and averaging the urban light exposure. A winter of lab night light sped up the males’ molting and boosted testosterone levels as well as organ development in spring. Continuing the night light treatment through the next winter left the males reproductively shut down in the spring of 2012. The lab night lights probably kept the birds’ seasonal reproductive clocks from resetting at the end of the first breeding season, Dominoni says. That second-year suppression may not be common in the real world, where birds fly around and experience more variety in night lighting, he says. But he sees the lab breeding shutdown as a sign of how big of an impact artificial light might have. © Society for Science & the Public 2000 - 2013
by Carrie Arnold ‘Tis the season for twinkling lights, wrapping paper, and virgin birth. For billions of Christians around the world, the holidays are a time to celebrate Jesus’s birth to the Virgin Mary. But for many animals, virgin birth is far from a miraculous event. Researchers have discovered a growing number of species that reproduce without assistance from the opposite sex. Known formally as parthenogenesis, virgin birth occurs when an embryo develops from an unfertilized egg cell. The development of an embryo usually requires genetic material from sperm and egg, as well as a series of chemical changes sparked by fertilization. In some parthenogenetic species, egg cells don’t undergo meiosis, the typical halving of the cell’s chromosomes, before dividing into new cells. These offspring are generally all female and clones of their mother. Other forms of parthenogenesis occur when two egg cells fuse after meiosis. Biologists think that sexual reproduction evolved as a way to mix the gene pool and reduce the impact of harmful mutations. Still, parthenogenesis can be beneficial if the mother is particularly well adapted to her environment, since all of her offspring will be just as well adapted. © 2010 American Association for the Advancement of Science.
by Kai Kupferschmidt Human beings tend to avoid places that smell of urine. But to mice, there is something positively addictive about the scent; they like to go back to a spot where they found the excretions again and again. Now, researchers have discovered that this behavior is triggered by a single protein in the urine of male mice. Mice use scent to mark their territory, advertise their social dominance, and convey information about their health and reproductive status. But these are usually volatile pheromones that disperse quickly, and it has remained unclear what exactly stimulates a female to be attracted to a specific male. Previous research had shown that female laboratory mice often return to a place where they have come across cage bedding soiled by males. Now, researchers at the University of Liverpool in the United Kingdom have confirmed this. Female mice spent five times as much time in a place where they had encountered a dish with male urine than at a place where they encountered water. Just 10 minutes of exposure to the urine was enough for the mice to show this place preference even after 14 days. However, if the mice were prevented from by a mesh screen touching the urine with their nose, the place seemed to lose its attractiveness. "That suggested that the story was not as simple as everybody assumed and volatile pheromones were not responsible," says behavioral ecologist Jane Hurst, one of the authors of the study. By separating the urine into different fractions, the scientists showed that a protein called darcin that they had identified in 2005—and which mice can only detect if their noses touch the urine—is responsible for the frequent visits. Pure darcin, produced in cell culture in the lab, elicited the same reaction, the authors report online today in Science. © 2010 American Association for the Advancement of Science.
by Elizabeth Norton From a strictly Darwinian viewpoint, homosexuality shouldn't still be around. It isn't the best way to pass along one's genes, and to complicate the picture further, no "gay genes" have even been identified. According to a newly released hypothesis, the explanation may not lie in DNA itself. Instead, as an embryo develops, sex-related genes are turned on and off in response to fluctuating levels of hormones in the womb, produced by both mother and child. This tug of war benefits the unborn child, keeping male or female development on a steady course even amid spikes in hormones. But if these so-called epigenetic changes persist once the child is born and has children of its own, some of those offspring may be homosexual, the study proposes. Evolutionary geneticist William Rice of the University of California, Santa Barbara, felt there had to be a reason why homosexuality didn't just fade away down the generations. Research estimates that about 8% of the population is gay, and homosexuality is known to run in families. If one of a set of identical twins is gay, there's a 20% probability that the other will be, too. Furthermore, Rice notes, "homosexuality isn't just a human thing." Among California gulls, which he watches from his office window, about 14% of pairs are female-female. In Australian black swans, some 6% of pairs are male-male, and 8% of male sheep are attracted exclusively to male partners. But many genetic screens have failed to turn up genes that are responsible for sexual orientation. So to find out what makes homosexuality persist, Rice and colleagues began a comprehensive survey of the literature. © 2010 American Association for the Advancement of Science
By Robert Martone The link between a mother and child is profound, and new research suggests a physical connection even deeper than anyone thought. The profound psychological and physical bonds shared by the mother and her child begin during gestation when the mother is everything for the developing fetus, supplying warmth and sustenance, while her heartbeat provides a soothing constant rhythm. The physical connection between mother and fetus is provided by the placenta, an organ, built of cells from both the mother and fetus, which serves as a conduit for the exchange of nutrients, gasses, and wastes. Cells may migrate through the placenta between the mother and the fetus, taking up residence in many organs of the body including the lung, thyroid muscle, liver, heart, kidney and skin. These may have a broad range of impacts, from tissue repair and cancer prevention to sparking immune disorders. It is remarkable that it is so common for cells from one individual to integrate into the tissues of another distinct person. We are accustomed to thinking of ourselves as singular autonomous individuals, and these foreign cells seem to belie that notion, and suggest that most people carry remnants of other individuals. As remarkable as this may be, stunning results from a new study show that cells from other individuals are also found in the brain. In this study, male cells were found in the brains of women and had been living there, in some cases, for several decades. What impact they may have had is now only a guess, but this study revealed that these cells were less common in the brains of women who had Alzheimer’s disease, suggesting they may be related to the health of the brain. © 2012 Scientific American