Links for Keyword: Sexual Behavior

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Researchers at the National Institutes of Health have uncovered firm evidence for what many mothers have long suspected: women’s brains appear to be hard-wired to respond to the cries of a hungry infant. Researchers asked men and women to let their minds wander, then played a recording of white noise interspersed with the sounds of an infant crying. Brain scans showed that, in the women, patterns of brain activity abruptly switched to an attentive mode when they heard the infant cries, whereas the men’s brains remained in the resting state. “Previous studies have shown that, on an emotional level, men and women respond differently to the sound of an infant crying,” said study co-author Marc H. Bornstein, Ph.D., head of the Child and Family Research Section of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the institute that conducted the study. “Our findings indicate that men and women show marked differences in terms of attention as well.” The earlier studies showed that women are more likely than men to feel sympathy when they hear an infant cry, and are more likely to want to care for the infant. Their findings appear in NeuroReport. Previous studies have shown differences in patterns of brain activity between when an individual’s attention is focused and when the mind wanders. The pattern of unfocused activity is referred to as default mode, Dr. Bornstein explained. When individuals focus on something in particular, their brains disengage from the default mode and activate other brain networks.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 18123 - Posted: 05.07.2013

By Scicurious In the great novel The Great Gatsby, Daisy, one of the love interests of the book, has a beautiful voice. She’s described otherwise, but you don’t really remember what she looked like, you remember how she sounded. Fitzgerald describes her voice as musical, running up and down and the scales when she talks. And you know what he’s talking about. You hear that voice in your head: light, breathy, utterly charming. You don’t really know what she looks like, but from imagining her voice, you know she is beautiful. What is it about this, or any voice, that makes it attractive? Is it the pitch? The tone? The firmness or breathiness of voice? And what is it about that voice, or any voice, that makes you know that someone is beautiful, handsome, masculine, feminine? The authors of this study wanted to see what makes a voice a VOICE. What acoustic factors make it most attractive to women and to men? To do this, they first took 10 young men, and had them rate the attractiveness of a female voice saying “good luck on your exams”. The voice actor said the phrase without any emotion using three different sound qualities: normal, breathy, and pressed (more of a hard tone). They then took the recording of this voice and modified it up and down, to create the phrase in several different pitches and formats. Specifically, they modified it upward toward what they hypothesized to mean “small body size and happiness” or downward toward what they hypothesized to mean “large body size and anger”. They showed that while increasing the pitch (higher) did not increase the attractiveness of the voice, lowering it decreased the attractiveness. And increasing the breathiness of the sentence increased attractiveness. The authors believe that this means that lowering the voice, and presumably indicating a larger body size (larger body size in general means the normal voice will be lower), reduced how attractive the men found the voice. © 2013 Scientific American

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 18122 - Posted: 05.06.2013

Symmetry study deemed a fraud Eugenie Samuel Reich Few researchers have tried harder than Robert Trivers to retract one of their own papers. In 2005, Trivers, an evolutionary biologist at Rutgers University in New Brunswick, New Jersey, published an attention-grabbing finding: Jamaican teenagers with a high degree of body symmetry were more likely to be rated ‘good dancers’ by their peers than were those with less symmetrical bodies. The study, which suggested that dancing is a signal for sexual selection in humans, was featured on the cover of this journal (W. M. Brown et al. Nature 438, 1148–1150; 2005). But two years later, Trivers began to suspect that the study data had been faked by one of his co-authors, William Brown, a postdoctoral researcher at the time. In seeking a retraction, Trivers self-published The Anatomy of a Fraud, a small book detailing what he saw as evidence of data fabrication. Later, Trivers had a verbal altercation over the matter with a close colleague and was temporarily banned from campus. An investigation of the case, completed by Rutgers and released publicly last month, now seems to validate Trivers’ allegations. Brown disputes the university’s finding, but it could help to clear the controversy that has clouded Trivers’ reputation as the author of several pioneering papers in the 1970s. For example, Trivers advanced an influential theory of ‘reciprocal altruism’, in which people behave unselfishly and hope that they will later be rewarded for their good deeds. He also analysed human sexuality in terms of the investments that mothers and fathers each make in child-rearing. © 2013 Nature Publishing Group

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 18114 - Posted: 05.04.2013

By Sophie Moura The year I was in fifth grade, I saw a television commercial for tampons. Like most 10-year-olds, I'd never heard of a tampon. But when I asked my mom what one was, she started crying. How do you tell your daughter that she's never going to need tampons? That she won't get her period or have babies, and that those things are the least of what sets her apart? From the outside, there was no sign that the little kid watching TV in a suburb of Pittsburgh was so different. I've always been girly — obsessed with dresses, sparkles, and the color pink, donning felt poodle skirts for Halloween and loving makeup. What isn't obvious is that I have a rare condition called androgen insensitivity syndrome, or AIS. I was born with XY chromosomes, the combination found in boys. With AIS, an XY embryo doesn't respond to the crucial hormones that tell the penis and scrotum to form. At the earliest stage of life, my body missed those signals, and I developed as a girl, with a clitoris and vulva. But what's inside me doesn't match. My parents learned this when I was 6. That year, I collapsed in the shower with a painful lump in my groin. Convinced I had a hernia, my parents, both doctors, rushed me to the hospital. But when surgeons operated (a hernia is tough to X-ray and needs to be fixed surgically), there was no twisted loop of intestine behind that bump. It was a testicle that had started descending. Across my abdomen, they found another one. The upper portion of my vagina, and my cervix, uterus, and fallopian tubes were missing. ©2013 Hearst Communication, Inc.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 18096 - Posted: 04.30.2013

Matt Kaplan By making noise that could potentially expose them to predators, young pied babblers get their parents to give them more attentions. Begging loudly has long been viewed as an offspring’s way of saying “I’m hungry”. But in predator-filled environments, these squawks can put young birds in harm's way, and may be a form of blackmail that forces parents to pay attention and feed the youngsters more than they might otherwise. The discovery comes from a three-year analysis of a well-studied community of pied babbler (Turdoides bicolor) in the Kalahari Desert of South Africa1. Alex Thompson of the University of Cape Town and colleagues from Britain and Australia, spent more than 200 hours observing the animals in the wild and recorded more than 3,000 incidents of parents feeding fledglings. Thompson and his team noted that fledglings were fed an average of 0.12 grams of food per minute when on the ground and away from cover, but just 0.03 grams per minute when begging from the safety of the trees. Furthermore, when the birds were played an audio recording of alarm calls indicating that a ground predator was in the vicinity, parents more than doubled the amount they gave to ground-based youngsters, but made no compensation for those in the trees. Fascinated, the team speculated that the young, which were slower than adults to respond to the alarm calls and cannot escape as quickly from danger, were intentionally putting themselves into a dangerous situation when hungry to force their parents to pay attention and feed them. © 2013 Nature Publishing Group,

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 18008 - Posted: 04.10.2013

By Felicity Muth With the historic supreme court hearings this week, there has been much discussion about homosexuality*. One of the ‘arguments’ that you often hear from the anti-gay rights side is that being gay isn’t natural. Evidence from the animal kingdom would refute this however, as same-sex behaviour is common and found in many different animals. There’s the famous example of ‘Roy’ and ‘Silo’, two male chinstrap penguins that formed a pair bond and raised a chick (‘Tango’) together, later turned into a distinctive children’s book (you can also read about their tragic breakup here – this part has yet to be made into a children’s book). Homosexuality is also common in many insects, and some flour beetle males actually mate 50% of the time with other males. But why does same-sex behaviour occur? How is it maintained by evolution? This is a complex question, and the answer is likely to differ from species to species. For example, flour beetle males that mate with other males can actually transfer to females this way. Other male insects like weevils or fruit flies may just not realise that the individual they’re mating with is also a male (it being better to mate with more animals, and get it ‘wrong’ sometimes, than be too discriminating and miss out on potentially fruitful mating attempts). However, in addition to specific cases, there may also be overarching patterns across species in how homosexuality is selected for and maintained by evolution. While many studies have concentrated on male-male sexual behaviour, females also engage in same-sex behaviour. Laysan albatrosses form female-female partnerships, performing the same mating rituals as in male-female pairs of this species, and these couples can last a lifetime. © 2013 Scientific American

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 17974 - Posted: 04.01.2013

By Meghan Rosen With parasitic flies gorging on her guts and the end approaching, a variable field cricket may have only one thing to do: Find a mate. Usually, female Gryllus lineaticeps prefer males with fast chirps. But when being eaten alive by fly larvae, female crickets don’t wait around for a snappy tune. Instead, they settle for slow-chirping sexual partners, evolutionary biologists Oliver Beckers of Indiana University in Bloomington and William Wagner Jr. of the University of Nebraska-Lincoln report in the April Animal Behaviour. Parasitic flies seek out crickets as potential homes (and meal tickets) for their young. Before the fly larvae chew through crickets’ bellies, female crickets have about a week to find a mate and lay eggs before dying. To find out whether infestation lowered females’ mating standards, Beckers and Wagner placed fly larvae on female crickets and then played slow and fast chirp recordings from loudspeakers set in separate corners of a square chamber. Healthy females walked toward the fast chirping sound about 80 percent of the time, while infested females split their devotion about equally. “They don’t invest a lot of time and energy finding the super sexy guy,” says Becker. “They’ll go for the average Joe.” © Society for Science & the Public 2000 - 2013

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 17956 - Posted: 03.27.2013

by Beth Skwarecki If you thought the battle of the genders was complicated, try having seven sexes. When Tetrahymena, a single-celled creature covered in cilia, mates, the offspring isn't necessarily the same sex as either parent—it can be any of seven. Now, researchers have figured out the complex dance of DNA that determines the offspring's sex, and it's a random selection, they report today in PLOS Biology. Each Tetrahymena has a gene for its own sex—or mating type—in its regular nucleus, but it also carries a second nucleus used only for reproduction. This "germline nucleus" contains incomplete versions of all seven mating type genes, which are cut and pasted together until one complete gene remains and the other six have been deleted. The newly rearranged DNA becomes part of the offspring's regular nucleus, determining its mating type. Because the mating type gene helps Tetrahymena recognize others of a different sex, the researchers say that the finding could shed light on how other cells, including those in humans, recognize those that are different from themselves. © 2010 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 17955 - Posted: 03.27.2013

By Darryl Fears, Ten years have gone by since one of the weirdest discoveries in the Chesapeake Bay region, on the south branch of the Potomac River — male smallmouth bass with lady parts, eggs in places where they absolutely should not be. Over that decade, wildlife biologists have probed the bay’s tributaries, slicing open fish for more necropsies than anyone can count. And one thing is clear: They still aren’t sure why between 50 and 100 percent of bass in various locations are gender-bending, switching from male to something called intersex. Biologists say studies are falling short because of a lack of data on the type and quantity of pesticides that run into the bay from farms. This complaint, along with other factors, prompted Democrats in the Maryland House and Senate to sponsor two bills in the current legislative session that would for the first time require growers to record their use of insecticides and herbicides and submit it to the state. The pesticide-reporting rule would create a treasure trove of data that scientists could draw from for studies on human and animal health, supporters say. Scientists could use it to focus research on chemical “hot spots,” the exact moment high concentrations of pesticides hit waters where vulnerable young fish are growing, said Vicki Blazer, a biologist who studies bass for the U.S. Geological Survey. But opponents say the bills have major drawbacks. They would create a financial burden for farmers, who would be forced to purchase updated equipment such as Global Positioning System devices to log pesticide applications, said Valerie Connelly, director of government relations for the Maryland Farm Bureau. © 1996-2013 The Washington Post

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 17912 - Posted: 03.18.2013

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.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 17856 - Posted: 02.27.2013

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.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
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,

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
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,

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 17796 - Posted: 02.13.2013

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

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 11: Emotions, Aggression, and Stress
Link ID: 17794 - Posted: 02.13.2013

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

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 11: Emotions, Aggression, and Stress
Link ID: 17793 - Posted: 02.13.2013

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

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 10: Biological Rhythms and Sleep
Link ID: 17748 - Posted: 02.04.2013

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

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
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

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 17725 - Posted: 01.29.2013

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.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 17641 - Posted: 12.29.2012

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

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory, Learning, and Development
Link ID: 17599 - Posted: 12.13.2012