Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases
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Posted by James Owen in Weird & Wild Bigger males may get a lot of attention, but sometimes being smaller—and sneakier—is more successful when it comes to mating. In the East African cichlid fish, Lamprologus callipterus, males come in two sizes: giants or dwarves that are 40 times smaller than their beefier rivals. (Watch a video of male cichlid fish fighting.) It’s an example of male polymorphism, a phenomenon in which males of the same species take different forms. Though people vary in height, men don’t come in two different sizes like the cichlids. Several research studies suggest that tall men—those over 5’7″—are more successful in dating and in their careers—but they get divorced at higher rates. But the variation in L. callipterus, which are found only in Lake Tanganyika (map), is “the most extreme there is,” said Michael Taborsky, co-director of the Institute of Ecology and Evolution at the University of Bern, Switzerland. “It’s an enormous size difference.” In a new study, published September 17 in the Proceedings of the Royal Society B, Taborsky and his team linked this gulf in size to the female’s unusual habit of laying eggs in empty snail shells. To attract females, the giant males collect hundreds of these shells, using their mouths to create nesting sites. But while their hefty build is ideal for lugging about the heavy shells and chasing off rivals, the giants can’t access the chambers of their female harem, instead releasing their sperm outside the shell, Taborsky explained. (Also see “Small Squid Have Bigger Sperm—And Their Own Sex Position.”) © 1996-2013 National Geographic Societ
Keyword: Sexual Behavior
Link ID: 20127 - Posted: 09.29.2014
by Laura Sanders Earlier this month, a star running back for the Minnesota Vikings was indicted for whipping his young son bloody with a switch. Leaked photographs allegedly showed Adrian Peterson’s 4-year-old son with cuts and bruises on his legs, back, buttocks and scrotum. As details about the incident emerged, Peterson took to Twitter to say that he’s not a perfect parent but what he did was not abuse. It was discipline. “My goal is always to teach my son right from wrong and that’s what I tried to do that day,” he wrote. Many people, and I’m one of them, that think Peterson’s actions were disgusting. There’s no way that hitting 4-year-old with a switch until his body is cut and bruised is a good way to impart values and morals. Peterson’s extreme actions, done in the name of corporal punishment, ignited a ferocious, emotionally fraught debate over whether it’s OK to hit your kid. The debate reflects deep divides in our society, chasms that track along political, religious, regional and racial lines. Half of all U.S. parents say they’ve spanked their kid. Spanking doesn’t just happen in the privacy of homes, either. Nineteen states allow teachers or principals to hit children. Opponents often point to scientific studies as proof that spanking is bad. And I confess, I originally thought this post was going to describe those results that we’ve all heard: how children who have been spanked are more aggressive and have more behavioral problems. But despite the headlines, the science behind spanking is actually quite limited, says clinical psychologist Christopher Ferguson of Stetson University in DeLand, Fla. “Because it’s a culture war issue, I think a lot of what we hear has misrepresented what is very nuanced science,” he says. © Society for Science & the Public 2000 - 2014.
by Sarah Zielinski Chimps may be cute and have mannerisms similar to humans, but they are wild animals. A new study finds that chimps raised as pets or entertainers have behavioral problems as adults. There are plenty of good reasons why chimpanzees should not be pets or performers, no matter how cute or humanlike they appear: They are wild animals. They can be violent with each other. And they can be violent toward humans — even humans that have a long history with the chimp. Plus, there’s evidence that seeing an adorable chimp dressed up like a miniature human actually makes us care less about the plight of their species. Now comes evidence that the way that chimps are raised to become pets or entertainers — taking them away from other chimps at a young age and putting them in the care of humans, who may or may not feed and care for them properly — has long-term, negative effects on their behavior. “We now add empirical evidence of the potentially negative welfare effects on the chimpanzees themselves as important considerations in the discussion of privately owned chimpanzees,” Hani Freeman and Stephen Ross of the Lincoln Park Zoo in Chicago write September 23 in PeerJ. Freeman and Ross compiled life history and behavioral data on 60 captive chimps living in zoos. Some of the animals had always lived in zoos and grew up in groups of chimpanzees. Six were raised solely by humans and were later placed in zoos after they became too big or too old for their owners to care for them. Others had a more mixed background. © Society for Science & the Public 2000 - 2014
// by Jennifer Viegas Harems -- where a group of females share a single mate -- can be sexual bliss for the male, but the arrangement poses many challenges for him, according to a new study. Male leaders of harems are often overworked and tired finds the study, published in the latest issue of Royal Society Open Science. Gelada baboons exemplify the problems. "Being a gelada leader male is fairly exhausting," co-author David Pappano told Discovery News. "In order to keep the females within his harem happy, gelada leader males spend a lot of time grooming them." "When bachelors are around, leader males often engage in costly displays -- running around, climbing up a tree, and producing a very loud (ee-yow) display call," added Pappano, who is an NSF postdoctoral research fellow at Princeton University's Department of Ecology and Evolutionary Biology. He co-authored the paper with Jacinta Beehner. © 2014 Discovery Communications, LLC.
Keyword: Sexual Behavior
Link ID: 20108 - Posted: 09.24.2014
By Melissa Dahl Recently, I was visiting my family in Seattle, and we were doing that thing families do: retelling old stories. As we talked, a common theme emerged. My brother hardly remembered anything from our childhood, even the stories in which he was the star player. (That time he fell down the basement steps and needed stitches in the ER? Nope. That panicky afternoon when we all thought he’d disappeared, only to discover he’d been hiding in his room, and then fell asleep? Nothing.) “Boys never remember anything,” my mom huffed. She’s right. Researchers are finding some preliminary evidence that women are indeed better at recalling memories, especially autobiographical ones. Girls and women tend to recall these memories faster and with more specific details, and some studies have demonstrated that these memories tend to be more accurate, too, when compared to those of boys and men. And there’s an explanation for this: It could come down to the way parents talk to their daughters, as compared to their sons, when the children are developing memory skills. To understand this apparent gender divide in recalling memories, it helps to start with early childhood—specifically, ages 2 to 6. Whether you knew it or not, during these years, you learned how to form memories, and researchers believe this happens mostly through conversations with others, primarily our parents. These conversations teach us how to tell our own stories, essentially; when a mother asks her child for more details about something that happened that day in school, for example, she is implicitly communicating that these extra details are essential parts to the story. © 2014 The Slate Group LLC
By JAMES GORMAN Are chimpanzees naturally violent to one another, or has the intrusion of humans into their environment made them aggressive? A study published Wednesday in Nature is setting off a new round of debate on the issue. The study’s authors argue that a review of all known cases of when chimpanzees or bonobos in Africa killed members of their own species shows that violence is a natural part of chimpanzee behavior and not a result of actions by humans that push chimpanzee aggression to lethal attacks. The researchers say their analysis supports the idea that warlike violence in chimpanzees is a natural behavior that evolved because it could provide more resources or territory to the killers, at little risk. But critics say the data shows no such thing, largely because the measures of human impact on chimpanzees are inadequate. While the study is about chimpanzees, it is also the latest salvo in a long argument about the nature of violence in people. In studying chimpanzee violence, “we’re trying to make inferences about human evolution,” said Michael L. Wilson, an anthropologist at the University of Minnesota and a study organizer. There is no disagreement about whether chimpanzees kill one another, or about some of the claims that Dr. Wilson and his 29 co-authors make. The argument is about why chimpanzees kill. Dr. Wilson and the other authors, who contributed data on killings from groups at their study sites, say the evidence shows no connection between human impact on the chimpanzee sites and the number of killings. He said the Ngogo group of chimpanzees in Uganda “turned out to be the most violent group of chimpanzees there is,” even though the site was little disturbed by humans. They have a pristine habitat, he said, and “they go around and kill their neighbors.” © 2014 The New York Times Company
|By Gary Stix A biochemical produced in the brain called oxytocin has entered popular culture in recent years as the “love,” “cuddle” or “bonding” hormone. That’s a lot to choose from. Oxytocin plays a role in producing contractions at childbirth and in helping in lactation, but we’ve known that for more than a century. Experiments in the 1990s showed that it was instrumental in leading prairie voles, known for their monogamous behavior, to pick a lifelong mate. Later studies then demonstrated that the chemical contributes to trust and social interactions in various animals, including humans. After the vole study, interest in the nine–amino acid peptide started to rise. In a TED talk economist Paul Zak called it “the moral molecule” because of its link to trust, empathy and prosperity. The Internet DIY brain-makeover market then took up the meme. Vero Labs of Daytona Beach, Fla., sells “Connekt” oxytocin spray for $79 that purports to “strengthen workplace bonds” and “increase positive self-awareness.” The company has also come out with a his-and-her“Attrakt” spray that mixes oxytocin with pheromones—chemical sex attractants that help mice get it on, but whose role in triggering mating behavior in humans is hotly disputed. (Researchers who study oxytocin warn prospective buyers away from these purchases, saying that long-term use in humans has not been studied.) © 2014 Scientific American
// by Richard Farrell Conventional thinking has long held that pelvic bones in whales and dolphins, evolutionary throwbacks to ancestors that once walked on land, are vestigial and will disappear millions of years from now. But researchers from University of Southern California and the Natural History Museum of Los Angeles County (NHM) have upended that assumption. The scientists argue in a paper just published in the journal Evolution that cetacean (whale and dolphin) pelvic bones certainly do have a purpose and that they're specifically targeted, by selection, for mating. The muscles that control a cetacean's penis are attached to the creature's pelvic bones. Matthew Dean, assistant professor at the USC Dornsife College of Letters, Arts and Sciences, and Jim Dines, collections manager of mammalogy at NHM, wanted to find out if pelvic bones could be evolutionarily advantageous by impacting the overall amount of control an individual creature has with its penis. The pair spent four years examining whale and dolphin pelvic bones, using a 3D laser scanner to study the shape and size of the samples in extreme detail. Then they gathered as much data as they could find -- reaching back to whaler days -- on whale testis size relative to body mass. The testis data was important because in nature, species in "promiscuous," competitive mating environments (where females mate with multiple males) develop larger testes, relative to their body mass, in order to outdo the competition. © 2014 Discovery Communications, LLC.
By Fredrick Kunkle Years ago, many scientists assumed that a woman’s heart worked pretty much the same as a man’s. But as more women entered the male-dominated field of cardiology, many such assumptions vanished, opening the way for new approaches to research and treatment. A similar shift is underway in the study of Alzheimer’s disease. It has long been known that more women than men get the deadly neurodegenerative disease, and an emerging body of research is challenging the common wisdom as to why. Although the question is by no means settled, recent findings suggest that biological, genetic and even cultural influences may play heavy roles. Of the more than 5 million people in the United States who have been diagnosed with Alzheimer’s, the leading cause of dementia, two-thirds are women. Because advancing age is considered the biggest risk factor for the disease, researchers largely have attributed that disparity to women’s longer life spans. The average life expectancy for women is 81 years, compared with 76 for men. Yet “even after taking age into account, women are more at risk,” said Richard Lipton, a physician who heads the Einstein Aging Study at Albert Einstein College of Medicine in New York. With the number of Alzheimer’s cases in the United States expected to more than triple by 2050, some researchers are urging a greater focus on understanding the underlying reasons women are more prone to the disease and on developing gender-specific treatments. The area of inquiry has been growing in part because of a push by female Alzheimer’s researchers, who have formed a group to advocate for a larger leadership role in the field and more gender-specific research.
By MATTHEW PERRONE AP Health Writer WASHINGTON (AP) — The Food and Drug Administration says there is little evidence that testosterone-boosting drugs taken by millions of American men are beneficial, though the agency is also unconvinced by studies suggesting the hormone carries serious risks. The agency posted its review online Wednesday ahead of a public meeting to discuss the benefits and risks of treatments that raise levels of the male hormone. Regulators agreed to convene the September 17 meeting after two federally funded studies found links between testosterone therapy and heart problems in men. The scrutiny comes amid an industry marketing blitz for new pills, patches and formulations that has transformed testosterone a multibillion-dollar market. Advertisements for prescription gels like Fortesta and Androgel promise aging men relief from ‘‘Low-T,’’ a condition they link to low libido, fatigue and weight gain. But FDA reviewers state that ‘‘the need to replace testosterone in these older men remains debatable.’’ While testosterone levels naturally decline after age 40, it’s unclear whether those lower levels actually lead to the signs commonly associated with aging, including decreased energy and loss of muscle. The FDA first approved testosterone injections in the 1950s for men who had been diagnosed with hypogonadism, a form of abnormally low testosterone caused by injury or medical illness. But the recent advertising push is focused on otherwise healthy men who simply have lower-than-normal levels of testosterone.
by Bethany Brookshire Premenstrual syndrome, or PMS, can be a miserable experience. Women report over 200 symptoms in the days before menstruation occurs. The complaints run the gamut from irritable mood to bloating. PMS can be so slight you don’t even notice, or it can be so severe it has its own category — premenstrual dysphoric disorder. But to some, PMS is just a punchline, a joke featured in pop culture from Buffy the Vampire Slayer to Saturday Night Live. Michael Gillings, who studies molecular evolution at Macquarie University in Sydney, thinks that PMS could have a purpose. In a perspective piece published August 11 in Evolutionary Adaptations, Gillings proposes that PMS confers an evolutionary advantage, increasing the likelihood that a woman will leave an infertile mate. He hopes that his idea could lead to more research and less stigma about the condition. But while his hypothesis certainly sparked a lot of discussion, whether it is likely, or even necessary, is in doubt. Gillings first began to think about PMS when he found out that premenstrual dysphoric disorder was being added to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders. “I started to think that we have a normal distribution of PMS responses, where some people don’t get any symptoms, the majority gets mild symptoms, and some get severe symptoms,” he explains. Including PMDD in DSM-5 made a statement, he says, that “we were going to take one end of this normal curve, the extreme far right end, and we were going to draw a line and say, those people there have a disease we’re going to label in our book. But if 80 percent of women get some kind of premenstrual symptoms, then it’s normal. And I wondered, if it’s so normal, what could be the reason for it?” © Society for Science & the Public 2000 - 2014.
By James Gallagher Health editor, BBC News website Breastfeeding can halve the risk of post-natal depression, according to a large study of 14,000 new mothers. However, there is a large increase in the risk of depression in women planning to breastfeed who are then unable to do so. The study, published in the journal Maternal and Child Health, called for more support for women unable to breastfeed. A parenting charity said mental health was a "huge issue" for many mothers. The health benefits of breastfeeding to the baby are clear-cut and the World Health Organization recommends feeding a child nothing but breast milk for the first six months. However, researchers at the University of Cambridge said the impact on the mother was not as clearly understood. 'Highest risk' One in 10 women will develop depression after the birth of their child. The researchers analysed data from 13,998 births in the south-west of England. It showed that, out of women who were planning to breastfeed, there was a 50% reduction in the risk of post-natal depression if they started breastfeeding. But the risk of depression more than doubled among women who wanted to, but were not able to, breastfeed. Dr Maria Iacovou, one of the researchers, told the BBC: "Breastfeeding does appear to have a protective effect, but there's the other side of the coin as well. "Those who wanted to and didn't end up breastfeeding had the highest risk of all the groups." BBC © 2014
By Kate Yandell Researchers have accumulated detailed knowledge of the neurons that drive male fruit flies’ mating behaviors. But the neurons that prompt females to respond—or not—to male overtures have been less-studied. Three papers published today (July 2) in Neuron and Current Biology begin to change that. They identify sets of neurons in female fruit flies that help process mating signals, modulate the insects’ receptivity to male courtship, and drive mating behavior. “These three groups independently identified important neuronal groups [that] are positioned in different points in the neuronal circuitry for regulating female receptivity,” said Daisuke Yamamoto, a behavioral geneticist at Tohoku University in Japan who was not involved in any of the studies. “We’ve had access to the male circuitry for a while now, and that’s turning out to be a really interesting way to study how behavior works,” said Jennifer Bussell, whose work as a PhD student at Rockefeller University contributed to the Current Biology paper. “Having that complementary circuit in the female can only provide more fodder for interesting experiments.” Female fruit flies’ mating behaviors depend on their reproductive state. They become receptive to mating as they mature, but become less receptive to males’ advances immediately after mating. If a female fruit fly is receptive to mating, she responds to male pheromones and courtship songs by engaging in a behavior called pausing, where she stops in her tracks near males so they can mount her and she opens her vaginal plates—hard coverings that protect her reproductive tract. © 1986-2014 The Scientist
Keyword: Sexual Behavior
Link ID: 19962 - Posted: 08.16.2014
by Laura Sanders In their first year, babies grow and change in all sorts of obvious and astonishing ways. As their bodies become longer, heavier and stronger, so do their brains. Between birth and a child’s first birthday, her brain nearly triples in size as torrents of newborn nerve cells create neural pathways. This incredible growth can be influenced by a baby’s early life environment, scientists have found. Tragic cases of severe neglect or abuse can throw brain development off course, resulting in lifelong impairments. But in happier circumstances, warm caregivers influence a baby’s brain, too. A new study in rats provides a glimpse of how motherly actions influence a pup’s brain. Scientists recorded electrical activity in the brains of rat pups as their mamas nursed, licked and cared for their offspring. The results, published in the July 21 Current Biology, offer a fascinating minute-to-minute look at the effects of parenting. Researchers led by Emma Sarro of New York University’s medical school implanted electrodes near six pups’ brains to record neural activity. Video cameras captured mother-pup interactions, allowing the scientists to link specific maternal behaviors to certain sorts of brain activity. Two types of brain patterns emerged: a highly alert state and a sleepier, zoned-out state, Sarro and colleagues found. Pups’ brains were alert while they were drinking milk and getting groomed by mom. Pups’ brains’ were similarly aroused when the pups were separated from their mom and siblings. Some scientists think that these bursts of brain activity help young brains form the right connections between regions. © Society for Science & the Public 2000 - 2013.
By Darryl Fears At first she was surprised. Then she was disturbed. Now she’s a little alarmed. Each time a different batch of male fish with eggs in their testes shows up in the Chesapeake Bay watershed, Vicki Blazer’s eyebrows arch a bit higher. In the latest study, smallmouth bass and white sucker fish captured at 16 sites in the Delaware, Ohio and Susquehanna rivers in Pennsylvania had crossed over into a category called intersex, an organism with two genders. “I did not expect to find it quite as widespread,” said Blazer, a U.S. Geological Survey biologist who studies fish. Since 2003, USGS scientists have discovered male smallmouth and largemouth bass with immature eggs in several areas of the Potomac River, including near the Blue Plains Advanced Wastewater Treatment Plant in the District. The previous studies detected abnormal levels of compounds from chemicals such as herbicides and veterinary pharmaceuticals from farms, and from sewage system overflows near smallmouth-bass nesting areas in the Potomac. Those endocrine-disrupting chemicals throw off functions that regulate hormones and the reproductive system. In the newest findings, at one polluted site in the Susquehanna near Hershey, Pa., 100 percent of male smallmouth bass that were sampled had eggs, Blazer said. With the mutant bass, she said, “we keep seeing . . . a correlation with the percent of agriculture in the watershed where we conduct a study.”
by Bethany Brookshire The deep ocean has spawned a new record: the longest egg-brooding period. In April 2007, Bruce Robison of the Monterey Bay Aquarium Research Institute in Moss Landing, Calif., and colleagues sent a remote-operated vehicle down 1,397 meters (4,583 feet) into the Monterey Submarine Canyon. There they saw a deep-sea octopus (Graneledone boreopacifica) making its way toward a stony outcrop. One month later, the scientists spotted the same octopus, which they dubbed ‘Octomom,’ on the rock with a clutch of 155 to 165 eggs. The researchers returned to the site 18 times in total. Each time, there she was with her developing eggs. Most female octopuses lay only one clutch of eggs, staying with the eggs constantly and slowly starving to death while protecting them from predators and keeping them clean. When the eggs hatch, the female dies. The scientists report July 30 in PLOS ONE that the octopus was observed on her eggs for 53 months, until September 2011, the longest brooding period of any known animal. B. Robison et al. Deep-sea octopus (Graneledone boreopacifica) conducts the longest-known egg-brooding period of any animal. PLOS ONE. Published online July 30, 2014. doi: 10.1371/journal.pone.0103437 © Society for Science & the Public 2000 - 2013.
Keyword: Sexual Behavior
Link ID: 19904 - Posted: 07.31.2014
Posted by Celeste Biever | The four females and one male are onboard a satellite as part of an experiment to investigate sexual activity and reproduction in microgravity carried out by Russia’s space agency. Roscosmos launched the lizards using a six-tonne Foton-M4 rocket on 19 July. But the fate of the tiny cosmonauts became uncertain when their satellite briefly lost contact with ground control on Thursday 24 July. Luckily, technicians managed to restore control on Saturday, and Roscosmos announced on its website that since then it has communicated with the satellite 17 times.”Contact is established, the prescribed commands have been conducted according to plan,” said Roscosmos chief Oleg Ostapenko. Keeping the geckos company are Drosophila fruit flies, as well as mushrooms, plant seeds and various microorganisms that are also being studied. There is also a special vacuum furnace on board, which is being used to analyse the melting and solidification of metal alloys in microgravity. Foton-M4 is set to carry out experiments over two months, and involves a “study of the effect of microgravity on sexual behaviour, the body of adult animals and embryonic development”, according to the website of the Institute of Medico-Biological Problems of the Russian Academy of Sciences, which has developed the project along with Roscosmos. Specific aims of the Gecko-F4 mission include: Create the conditions for sexual activity, copulation and reproduction of geckos in orbit Film the geckos’ sex acts and potential egg-laying and maximise the likelihood that any eggs survive Detect possible structural and metabolic changes in the animals, as well as any eggs and foetuses © 2014 Macmillan Publishers Limited.
Keyword: Sexual Behavior
Link ID: 19896 - Posted: 07.30.2014
By PAUL VITELLO The conventional wisdom among animal scientists in the 1950s was that birds were genetically programmed to sing, that monkeys made noise to vent their emotions, and that animal communication, in general, was less like human conversation than like a bodily function. Then Peter Marler, a British-born animal behaviorist, showed that certain songbirds not only learned their songs, but also learned to sing in a dialect peculiar to the region in which they were born. And that a vervet monkey made one noise to warn its troop of an approaching leopard, another to report the sighting of an eagle, and a third to alert the group to a python on the forest floor. These and other discoveries by Dr. Marler, who died July 5 in Winters, Calif., at 86, heralded a sea change in the study of animal intelligence. At a time when animal behavior was seen as a set of instinctive, almost robotic responses to environmental stimuli, he was one of the first scientists to embrace the possibility that some animals, like humans, were capable of learning and transmitting their knowledge to other members of their species. His hypothesis attracted a legion of new researchers in ethology, as animal behavior research is also known, and continues to influence thinking about cognition. Dr. Marler, who made his most enduring contributions in the field of birdsong, wrote more than a hundred papers during a long career that began at Cambridge University, where he received his Ph.D. in zoology in 1954 (the second of his two Ph.D.s.), and that took him around the world conducting field research while teaching at a succession of American universities. Dr. Marler taught at the University of California, Berkeley, from 1957 to 1966; at Rockefeller University in New York from 1966 to 1989; and at the University of California, Davis, where he led animal behavior research, from 1989 to 1994. He was an emeritus professor there at his death. © 2014 The New York Times Company
By Michael Brooks Occasionally, scientific research comes up with banal findings that should nonetheless stop us in our tracks. For example, researchers recently published a study showing that a father’s brain will change its hormonal outputs and neural activity depending on his parenting duties. The conclusion of the research is, in essence, that men make good parents, too. Surely this is not news. Yet it does provide evidence that is sadly still useful. Those involved with issues of adoption, fathers’ rights, gay rights, child custody, and religion-fuelled bigotry will all benefit from understanding what we now know about what makes a good parent. The biggest enemy of progress has been the natural world, or at least our view of it. Females are the primary caregivers in 95 percent of mammal species. That is mainly because of lactation. Infants are nourished by their mothers’ milk, so it makes sense for most early caring to be done by females. Human beings, however, have developed more sophisticated means of nourishing and raising our offspring. Should the circumstances require a different set-up, we have ways to cope. It turns out that this is not just in terms of formula milk, nannies or day care: We also have a flexible brain. The new study, published in Proceedings of the National Academy of Sciences, scanned the brains of parents while they watched videos of their interactions with their children. The researchers found that this stimulated activity in two systems of the brain. One is an emotional network that deals with social bonding, ensures vigilance and coordinates responses to distress, providing chemical rewards for behaviours that maintain the child’s well-being. The other network is concerned with mental processing. It monitors the child’s likely state of mind, emotional condition, and future needs, allowing for planning. 2014 © The New Republic.
Keyword: Sexual Behavior
Link ID: 19883 - Posted: 07.26.2014
By Helen Briggs Health editor, BBC News website The timing of when a girl reaches puberty is controlled by hundreds of genes, say scientists. And age at first period may vary in daughters from the same family because of genetic factors, research shows. The findings, published in Nature, could give clues to why early puberty may be linked to an increased risk of health conditions. Scientists at 166 institutions analysed the DNA of more than 180,000 women in one of the largest studies of its kind. They found that hundreds of genes were involved in the timing of puberty. Unusually, a girl's first period was also influenced by imprinted genes - a rare event where genes from either the mother of father are silenced. "Our findings imply that in a family, one parent may more profoundly affect puberty timing in their daughters than the other parent," said lead researcher Dr John Perry of the University of Cambridge. He said the biological complexity revealed in the study was "amazing". "We identified more than 100 regions of the genome associated with puberty timing, but our analysis suggests there are likely to be thousands," he told BBC News. Lifestyle BBC © 2014