Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases
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By Jessica Boddy Activity trackers like Fitbits and Jawbones help fitness enthusiasts log the calories they burn, their heart rates, and even how many flights of stairs they climb in a day. Biologist Cory Williams of Northern Arizona University in Flagstaff is using similar technology to track the energy consumption of arctic ground squirrels in Alaska—insight that may reveal how the animals efficiently forage for food while avoiding being picked off by golden eagles. This week, Williams published a study in Royal Society Open Science that compared the activity levels of male and female squirrels. He found that although males spend a lot more time outside of their burrows, they’re pretty lazy, and sometimes just bask in the sun during warmer months. Females, on the other hand, have limited time to spare when caring for their young, and use it to run around and forage for themselves and their babies. In addition to previous work on arctic ground squirrel hibernation and seasonal differences in behavior, the finding is helping his team figure out why males tend to be more susceptible to being eaten. Williams sat down with Science to talk about creating a squirrel Fitbit, catching the animals in the wild, and how technology is improving ecological research. This interview has been edited for brevity and clarity. Q: What got you interested in studying arctic ground squirrels? A: It’s one of the only arctic animals that keeps a rigid schedule even when there’s no light/dark cycle for 6 week—meaning, they emerge from and return to their burrows the same time every day and they eat the same time each day, even though the sun stays in the sky for weeks and weeks. So I started to deploy the energy tracking technologies to better understand how the squirrels use energy through the seasons. © 2016 American Association for the Advancement of Science
Keyword: Sexual Behavior
Link ID: 22714 - Posted: 09.30.2016
By Clare Wilson IT HAS been blamed for brain shrinkage, impotence, divorce and paedophilia – and in April this year, Utah declared it a public health hazard. Warnings about pornography come not just from religious or conservative groups – former Playboy model and actor Pamela Anderson also recently cautioned against its “corrosive effects”. Yet survey after survey shows porn use is common among men and not exactly rare in women, so can it really be so dangerous? Or could it even have benefits? While there is research into the effects of porn, a great deal of it is contradictory. Even the same studies are interpreted differently by those on opposite sides of the debate. Some feel it is a menace to society, while others think that attitude belongs with 1980s hysteria over video nasties. Anti-porn campaigners chiefly argue that it is addictive and hijacks the brain’s normal reward pathways. Like heroin addicts who crave more of their drug to get the same high, users find they are no longer aroused by real sex and resort to increasingly harder-core material, or so the theory goes. Of course, there are other concerns over pornography, such as its depictions of violence, exploitation and sexual consent. But male addiction is an increasing focus of anti-porn campaigns. Campaigners say that an excess of porn prompts users to spurn their partners and seek out images of bestiality, rape scenes, and child abuse. Some schools in Scotland now warn that viewing adult images leads to impotence, coercion and abuse. “This kind of escalation is described over and over again,” says Gary Wilson, a retired biology lecturer and author of website and book Your Brain on Porn. © Copyright Reed Business Information Ltd.
Keyword: Sexual Behavior
Link ID: 22706 - Posted: 09.29.2016
By Karl Gruber Five lionesses in Botswana have grown a mane and are showing male-like behaviours. One is even roaring and mounting other females. Male lions are distinguished by their mane, which they use to attract females, and they roar to protect their territory or call upon members of their pride. Females lack a mane and are not as vocal. . New Scientist Live: Book tickets to our festival of ideas and discovery – 22 to 25 September in London But sometimes lionesses grow a mane and even behave a bit like males. However, until now, reports of such maned lionesses have been extremely rare and largely anecdotal. We knew they existed, but little about how they behave. Now, Geoffrey D. Gilfillan at the University of Sussex in Falmer, UK, and colleagues have reported five lionesses sporting a mane at the Moremi Game Reserve in Botswana’s Okavango delta. Gilfillan started studying these lionesses back in March 2014, and for the next two years he focused on recording the behaviour of one of them, called SaF05. She had an underdeveloped mane and was larger than most females. “While SaF05 is mostly female in her behaviour – staying with the pride, mating males – she also has some male behaviours, such as increased scent-marking and roaring, as well as mounting other females,” says Gilfillan. © Copyright Reed Business Information Ltd.
By Colin Barras It is not just about speed. The only songbird known to perform a rapid tap dance during courtship makes more noise with its feet during its routines than at other times. The blue-capped cordon-bleu (Uraeginthus cyanocephalus) from East Africa is blessed with the attributes of a Broadway star: striking good looks, a strong singing voice – and fine tap-dancing skills. The dances are so fast that they went unnoticed until 2015, when Masayo Soma at Hokkaido University in Japan and her colleagues captured the performances on high-speed film. The bird’s speciality is a left-right-left shuffle – only with the feet striking the perch up to 50 times a second. The vision of some birds operates at a faster rate than that of humans, so the cordon-bleu’s dance may simply be about creating an impressive visual performance. But it could also be about winning over a potential mate with rhythm. To explore the idea, Soma and her colleagues recorded audio of the courtship dances, which both males and females perform. They found that the tap dances are unusually loud: the feet strike the branch with enough force to generate sound averaging 30 decibels. This typically drops to just 20 decibels when a bird’s feet strike the branch as it hops around when it is not performing, which means the step sounds are not just a by-product of movement. © Copyright Reed Business Information Ltd.
Keyword: Sexual Behavior
Link ID: 22665 - Posted: 09.19.2016
Carrie Arnold Could a protein that originated in a virus explain why men are more muscular than women? Viruses are notorious for their ability to cause disease, but they also shape human biology in less obvious ways. Retroviruses, which insert their genetic material into our genomes to copy themselves, have left behind genes that help to steer our immune systems and mold the development of embryos and the placenta. Now researchers report in PLOS Genetics that syncytin, a viral protein that enables placenta formation, also helps to increase muscle mass in male mice1. These results could partially explain a lingering mystery in biology: why the males of many mammalian species tend to be more muscular than females. “As soon as I read it, my mind started racing with the potential implications,” says evolutionary virologist Aris Katzourakis of the University of Oxford, UK. About 8% of the 3 billion pairs of As, Ts, Gs and Cs that make up our DNA are viral detritus. Many of those viral hand-me-downs have degraded into useless junk — but not all, as a series of discoveries over the past 15 years has revealed. In 2000, scientists discovered that syncytin, a protein that enables the formation of the placenta, actually originated as a viral protein that humans subsequently ‘borrowed’2. That original viral protein enables the retrovirus to fuse with host cells, depositing its entire genome into the safe harbour of the cytoplasm. Syncytin has changed little from this ancestral protein form; it directs certain placental cells to fuse with cells in the mother’s uterus, forming the outer layer of the placenta. © 2016 Macmillan Publishers Limited
By NATALIE ANGIER The female bonobo apes of the Wamba forest in the Democratic Republic of Congo had just finished breakfast and were preparing for a brief nap in the treetops, bending and crisscrossing leafy branches into comfortable day beds. But one of the females was in estrus, her rump exceptionally pink and swollen, and four males in the group were too excited to sleep. They took turns wildly swinging and jumping around the fertile female and her bunkmates, shaking the branches, appearing to display their erections and perforating the air with high-pitched screams and hoots. Suddenly, three older, high-ranking female bonobos bolted up from below, a furious blur of black fur and swinging limbs and, together with the female in estrus, flew straight for the offending males. The males scattered. The females pursued them. Tree boughs bounced and cracked. Screams on all sides grew deafening. Three of the males escaped, but the females cornered and grabbed the fourth one — the resident alpha male. He was healthy, muscular and about 18 pounds heavier than any of his captors. But no matter. The females bit into him as he howled and struggled to pull free. Finally, “he dropped from the tree and ran away, and he didn’t appear again for about three weeks,” said Nahoko Tokuyama, of the Primate Research Institute at Kyoto University in Japan, who witnessed the encounter. When the male returned, he kept to himself. Dr. Tokuyama noticed that the tip of one of his toes was gone. “Being hated by females,” she said in an email interview, “is a big matter for male bonobos.” The toe-trimming incident was extreme but not unique. Describing results from their long-term field work in the September issue of Animal Behaviour, Dr. Tokuyama and her colleague Takeshi Furuichi reported that the female bonobos of Wamba often banded together to fend off male aggression, and in patterns that defied the standard primate rule book. © 2016 The New York Times Company
By Jesse Singal Back in 2014, a bigoted African leader put J. Michael Bailey, a psychologist at Northwestern, in a strange position. Yoweri Museveni, the president of Uganda, had been issuing a series of anti-gay tirades, and — partially fueled by anti-gay religious figures from the U.S. — was considering toughening Uganda’s anti-gay laws. The rhetoric was getting out of control: “The commercialisation of homosexuality is unacceptable,” said Simon Lokodo, Uganda’s ethics minister. “If they were doing it in their own rooms we wouldn’t mind, but when they go for children, that’s not fair. They are beasts of the forest.” Eventually, Museveni said he would table the idea of new legislation until he better understood the science of homosexuality, and agreed to lay off Uganda’s LGBT population if someone could prove to him homosexuality was innate. That’s where Bailey comes in: He’s a leading sex researcher who has published at length on the question of where sexual orientation comes from. LGBT advocates began reaching out to him to explain the science of homosexuality and, presumably, denounce Museveni for his hateful rhetoric. But “I had issues with rushing out a scientific statement that homosexuality is innate,” he said in an email, because he’s not sure that’s quite accurate. While he did write articles, such as an editorial in New Scientist, explaining why he thought Museveni’s position didn’t make sense, he stopped short of calling homosexuality innate. He also realized that in light of some recent advances in the science of sexual orientation, it was time to publish an article summing up the current state of the field — gathering together all that was broadly agreed-upon about the nature and potential origins of sexual orientation. (In the meantime, Museveni did end up signing the anti-gay legislation, justifying his decision by reasoning that homosexuality “was learned and could be unlearned.”) © 2016, New York Media LLC.
By Simon Oxenham It can seem like barely a week goes by without a new study linking the stage in a woman’s monthly cycle to her preferences in a sexual partner. Reportedly, when women are ovulating they are attracted to men who are healthier, more dominant, more masculine, have higher testosterone levels– the list goes on. But do women really exhibit such behavioural changes – and why are we so fascinated by the idea that they do? A popular theory in evolutionary psychology is that women seek out men with better genes while they are ovulating to have short term affairs with, so as to produce healthier babies. These men may not necessarily stick around for the long haul, but appear particularly attractive when a woman is in the fertile stage of her cycle. During the non-fertile phase, the theory goes that women seek out men who are more likely to make reliable long-term partners and good fathers. But something smells a bit fishy here. Are women really evolutionarily hard-wired to cuckold their partners? Or might the attraction of a salacious hypothesis – with slightly sexist overtones – be shaping some of this research? Masculine all month A review of these kinds of studies is now challenging this often-told story. Wendy Wood at the University of Southern California and her team have analysed 58 studies – some of which were never published – and found that this theory is largely unsupported by evidence. © Copyright Reed Business Information Ltd.
By Christie Aschwanden The Olympic stadium was quiet on Wednesday morning, and spectators in the sparsely filled stands seemed to pay little notice to South African runner Caster Semenya as she cruised to an easy win in her first-round heat of the 800 meters. But on Saturday evening, when Semenya will contest the 800-meter final, she’ll have the world’s eyes on her. “There is no more certain gold medal in the Rio Olympics than Semenya,” wrote Ross Tucker, an exercise scientist in South Africa, on his blog, The Science of Sport. “She could trip and fall, anywhere in the first lap, lose 20m, and still win the race.” If she does indeed dominate, some sports fans will be cheering Semenya, while others will be less inclined to celebrate, believing that she has an unfair advantage over her rivals. Semenya made headlines in 2009 amid rumors that track’s governing body, the International Association of Athletics Federations, had required her to undergo tests to confirm that she was female. Media accounts have reported that she has hyperandrogenism, a condition that causes higher-than-average testosterone levels — an allegation that neither Semenya nor the IAAF has publicly confirmed. Semenya’s case is the latest saga in sport’s checkered history of sex testing, a task that is purportedly aimed at creating an even playing field but — as I’ve discussed previously — raises serious questions about how athletics organizations treat women. Her muscular build, deep voice and remarkable results had raised suspicions among some of Semenya’s rivals about whether she was really a woman. “Just look at her,” said Mariya Savinova, a Russian runner now tangled in her country’s doping scandal.
By Melinda Wenner Moyer The science of sleep is woefully incomplete, not least because research on the topic has long ignored half of the population. For decades, sleep studies mostly enrolled men. Now, as sleep researchers are making a more concerted effort to study women, they are uncovering important differences between the sexes. Hormones are a major factor. Estrogen, progesterone and testosterone can influence the chemical systems in the brain that regulate sleep and arousal. Moreover, recent studies indicate that during times of hormonal change—such as puberty, pregnancy and menopause—women are at an increased risk for sleep disorders such as obstructive sleep apnea, restless legs syndrome and insomnia. Women also tend to report that they have more trouble sleeping before and during their menstrual periods. And when women do sleep poorly, they may have a harder time focusing than sleep-deprived men do. In one recent study, researchers shifted the sleep-wake cycles of 16 men and 18 women for 10 days. Volunteers were put on a 28-hour daily cycle involving nearly 19 hours of awake time followed by a little more than nine hours of sleep. During the sleep-shifted period, the women in the group performed much less accurately than the men on cognitive tests. The findings, published in April of this year in the Proceedings of the National Academy of Sciences USA, may help explain why women are more likely than men to get injured working graveyard shifts. In addition, a study conducted in 2015 in teenagers reported that weekday sleep deprivation affects cognitive ability more in girls than in boys. © 2016 Scientific American
by Helen Thompson Some guys really know how to kill a moment. Among Mediterranean fish called ocellated wrasse (Symphodus ocellatus), single males sneak up on mating pairs in their nest and release a flood of sperm in an effort to fertilize some of the female’s eggs. But female fish may safeguard against such skullduggery through their ovarian fluid, gooey film that covers fish eggs. Suzanne Alonzo, a biologist at Yale University, and her colleagues exposed sperm from both types of males to ovarian fluid from female ocellated wrasse in the lab. Nesting males release speedier sperm in lower numbers (about a million per spawn), while sneaking males release a lot of slower sperm (about four million per spawn). Experiments showed that ovarian fluid enhanced sperm velocity and motility and favored speed over volume. Thus, the fluid gives a female’s chosen mate an edge in the race to the egg, the researchers report August 16 in Nature Communications. While methods to thwart unwanted sperm are common in species that fertilize within the body, evidence from Chinook salmon previously hinted that external fertilizers don’t have that luxury. However, these new results suggest otherwise: Some female fish retain a level of control over who fathers their offspring even after laying their eggs. Male ocellated wrasse come in three varieties: sneaky males (shown) that surprise mating pairs with sperm but don’t help raise offspring; nesting males that build algae nests and court females; and satellite males, which protect nests from sneakers but staying out of parenting. |© Society for Science & the Public 2000 - 2016
Carl Zimmer An eye is for seeing, a nose is for smelling. Many aspects of the human body have obvious purposes. But some defy easy explanation. For biologists, few phenomena are as mysterious as the female orgasm. While orgasms have an important role in a woman’s intimate relationships, the evolutionary roots of the experience — a combination of muscle contractions, hormone release, and intense pleasure — have been difficult to uncover. For decades, researchers have put forward theories, but none are widely accepted. Now two evolutionary biologists have joined the fray, offering a new way of thinking about the female orgasm based on a reconstruction of its ancient history. On Monday, in The Journal of Experimental Zoology, the authors conclude that the response originated in mammals more than 150 million years ago as a way to release eggs to be fertilized after sex. Until now, few scientists have investigated the biology of distantly related animals for clues to the mystery. “For orgasms, we kept it reserved for humans and primates,” said Mihaela Pavlicev, an evolutionary biologist at University of Cincinnati College of Medicine and an author of the new paper. “We didn’t look to other species to dig deeper and look for the origin.” The male orgasm has never caused much of a stir among evolutionary biologists. The pleasure is precisely linked to ejaculation, the most important step in passing on a male’s genes to the next generation. That pleasure encourages men to deliver more sperm, which is evolutionarily advantageous. For women, the evolutionary path is harder to figure out. The muscle contractions that occur during an orgasm are not essential for a woman to become pregnant. And while most men can experience an orgasm during sex, it’s less reliable for women. © 2016 The New York Times Company
Nicola Davis Female orgasm has perplexed scientists, fuelled an equality movement and propelled Meg Ryan to fame. Now researchers say they might have found its evolutionary roots. The purpose of the euphoric sensation has long puzzled scientists as it is not necessary for conception, and is often not experienced by women during sex itself. But scientists in the US have come up with an answer. Human female orgasm, they say, might be a spin-off from our evolutionary past, when the hormonal surges that accompany it were crucial for reproduction. “It is important to stress that it didn’t look like the human female orgasm looks like now,” said Mihaela Pavličev, co-author of the study from Cincinnati children’s hospital. “We think that [the hormonal surge] is the core that was maybe modified further in humans.” Writing in the journal JEZ-Molecular and Developmental Evolution, Pavličev and co-author Günter Wagner from Yale University describe how they delved into the anatomy and behaviour of a host of placental mammals to uncover the evolutionary origin of female orgasm, based on the hormonal surges associated with it. In mammals such as cats and rabbits, these surges occur during sex and play a crucial role in signalling for eggs to be released from the female’s ovaries. By contrast in a variety of other mammals, including humans and other primates, females ovulate spontaneously. © 2016 Guardian News and Media Limited
By PAM BELLUCK The World Health Organization is moving toward declassifying transgender identity as a mental disorder in its global list of medical conditions, with a new study lending additional support to a proposal that would delete the decades-old designation. The change, which has so far been approved by each committee that has considered it, is under review for the next edition of the W.H.O. codebook, which classifies diseases and influences the treatment of patients worldwide. “The intention is to reduce barriers to care,” said Geoffrey Reed, a psychologist who is coordinating the mental health and behavior disorders section in the upcoming edition of the codebook, called the International Classification of Diseases, or I.C.D. Dr. Reed, a professor at the National Autonomous University of Mexico and an author of the new study, said the proposal to remove transgender from the mental disorder category was “not getting opposition from W.H.O.,” suggesting that it appears likely to be included in the new edition. The revised volume would be the first in more than 25 years, and is scheduled to be approved in May 2018. Removing the mental health label from transgender identity would be a powerful signifier of acceptance, advocates and mental health professionals say. “It’s sending a very strong message that the rest of the world is no longer considering it a mental disorder,” said Dr. Michael First, a professor of clinical psychiatry at Columbia University and the chief technical consultant to the new edition of the codebook, which is known by its initials and the edition number I.C.D.-11. “One of the benefits of moving it out of the mental disorder section is trying to reduce stigma.” © 2016 The New York Times Company
Keyword: Sexual Behavior
Link ID: 22484 - Posted: 07.27.2016
By Jesse Singal As anyone who has read much about the subject can attest, the discussion about kids with gender dysphoria — that is, discomfort with their body and the feeling that they should have been born the other sex, or that they are the other sex — can get extremely heated and tricky. Much of the controversy stems from questions of age: How young is too young to help a child socially transition — that is, to change their name and pronoun, and possibly the way they present themselves? To prescribe them cross-sex hormones to begin the process of physically transitioning? For children with persistent gender dysphoria who are approaching adolescence, current best practice is to prescribe them so-called puberty blockers. Delaying the onset of puberty both forestalls the sometimes very uncomfortable experience of a child going through puberty in a body they aren’t comfortable in, and buys them and their families time to figure out what to do. Sometimes, this eventually leads to the prescription of cross-sex hormones, and sometimes it leads to surgery after that. Some people, though, are arguing that kids — particularly those who have socially transitioned at a young age — shouldn’t have to wait that long. Recently in the Guardian, for example, Kate Lyons reported on the current state of this debate in Britain: specifically, whether children who identify as transgender should be given access to cross-sex hormones, or possibly even surgery, at younger ages than what is current practice. © 2016, New York Media LLC.
Keyword: Sexual Behavior
Link ID: 22483 - Posted: 07.27.2016
By Andy Coghlan The final brain edit before adulthood has been observed for the first time. MRI scans of 300 adolescents and young adults have shown how the teenage brain upgrades itself to become quicker – but that errors in this process may lead to schizophrenia in later life. The editing process that takes place in teen years seems to select the brain’s best connections and networks, says Kirstie Whitaker at the University of Cambridge. “The result is a brain that’s sleeker and more efficient.” When Whitaker and her team scanned brains from people between the ages of 14 and 24, they found that two major changes take place in the outer layer of the brain – the cortex – at this time. As adolescence progresses, this layer of grey matter gets thinner – probably because unwanted or unused connections between neurons – called synapses – are pruned back. At the same time, important neurons are upgraded. The parts of these cells that carry signals down towards synapses are given a sheath that helps them transmit signals more quickly – a process called myelination. “It may be that pruning and myelination are part of the maturation of the brain,” says Steven McCarroll at Harvard Medical School. “Pruning involves removing the connections that are not used, and myelination takes the ones that are left and makes them faster,” he says. McCarroll describes this as a trade-off – by pruning connections, we lose some flexibility in the brain, but the proficiency of signal transmission improves. © Copyright Reed Business Information Ltd.
Keyword: Development of the Brain
Link ID: 22474 - Posted: 07.26.2016
By Knvul Sheikh Although millions of women use hormone therapy, those who try it in hopes of maintaining sharp memory and preventing the fuzzy thinking sometimes associated with menopause may be disappointed. A new study indicates that taking estrogen does not significantly affect verbal memory and other mental skills. “There is no change in cognitive abilities associated with estrogen therapy for postmenopausal women, regardless of their age,” says Victor Henderson, a neurologist at Stanford University and the study’s lead author. Evidence of positive and negative effects of such hormone therapy has ping-ponged over the years, with some observational studies in postmenopausal women and research in animal models, suggesting it improves cognitive function and memory. But other previous research, including a long-term National Institutes of Health Women’s Health Initiative memory study published in 2004, has suggested that taking estrogen increases the risk of cognitive impairment and dementia in women over 65 years old. Henderson says one explanation for these contradictory findings may be that after menopause begins there is a “critical period” in which hormone therapy could still benefit relatively young women—if they start early enough. So in their study, which appears in the July 20 online Neurology, Henderson and his team recruited 567 healthy women, between ages 41 and 84, to examine how estrogen affected one group whose members were within six years of their last menstrual period and another whose members had started menopause at least 10 years earlier. © 2016 Scientific American
By Karl Gruber For most birds the night brings a well-deserved rest. But for some, it is time for more risqué activities. Nocturnal birds sing at night – no surprises there – mainly to attract mates or repel rivals, the same reasons other birds sing at daytime. But a small number of species active by day also occasionally sing at night. Why they invest time and energy in such behaviour has been something of a mystery. Now Antonio Celis-Murillo at the Illinois Natural History Survey in Champaign and his colleagues think they have an answer – and it wasn’t what they expected. The team spent two years studying field sparrows, Spizella pusilla, a common bird across eastern North America. Active during the day, these birds are territorial and largely monogamous, though they engage in occasional infidelity. The researchers observed 28 pairs in the wild, recording the songs of territorial males, as well as those of intruder and neighbouring males. They then conducted playback experiments at night, studying the responses of the pairs. “I was surprised to see what these birds were up to,” says Celis-Murillo. The males sing to attract other male’s partners, and these females are all too willing to wake up for a night-time rendezvous. The team also found that males sang more during periods when females were reproductively receptive, and that the females responded to such song more often when they were fertile. The female’s mate didn’t appear to kick up a fuss and counter-sing – which would be expected if nocturnal songs served to repel rivals. © Copyright Reed Business Information Ltd.
By Jessica Hamzelou TEENAGE pregnancies have hit record lows in the Western world, largely thanks to increased use of contraceptives of all kinds. But strangely, we don’t really know what hormonal contraceptives – pills, patches and injections that contain synthetic sex hormones – are doing to the developing bodies and brains of teenage girls. You’d be forgiven for assuming that we do. After all, the pill has been around for more than 50 years. It has been through many large trials assessing its effectiveness and safety, as have the more recent patches and rings, and the longer-lasting implants and injections. But those studies were done in adult women – very few have been in teenage girls. And biologically, there is a big difference. At puberty, our bodies undergo an upheaval as our hormones go haywire. It isn’t until our 20s that things settle down and our brains and bones reach maturity. “If a drug is going to be given to 11 and 12-year-olds, it needs to be tested in 11 and 12-year-olds,” says Joe Brierley of the clinical ethics committee at Great Ormond Street Hospital in London. Legislation introduced in the US in 2003 and in Europe in 2007 was intended to make this happen but a New Scientist investigation can reveal that there is still scant data on what contraceptives actually do to developing girls. The few studies that have been done suggest that tipping the balance of oestrogen and progesterone during this time may have far-reaching effects, although there is not yet enough data to say whether we should be alarmed. © Copyright Reed Business Information Ltd.
Carl Zimmer Our genes are not just naked stretches of DNA. They’re coiled into intricate three-dimensional tangles, their lengths decorated with tiny molecular “caps.” These so-called epigenetic marks are crucial to the workings of the genome: They can silence some genes and activate others. Epigenetic marks are crucial for our development. Among other functions, they direct a single egg to produce the many cell types, including blood and brain cells, in our bodies. But some high-profile studies have recently suggested something more: that the environment can change your epigenetic marks later in life, and that those changes can have long-lasting effects on health. In May, Duke University researchers claimed that epigenetics could explain why people who grow up poor are at greater risk of depression as adults. Even more provocative studies suggest that when epigenetic marks change, people can pass them to their children, reprogramming their genes. But criticism of these studies has been growing. Some researchers argue that the experiments have been weakly designed: Very often, they say, it’s impossible for scientists to confirm that epigenetics is responsible for the effects they see. Three prominent researchers recently outlined their skepticism in detail in the journal PLoS Genetics. The field, they say, needs an overhaul. “We need to get drunk, go home, have a bit of a cry, and then do something about it tomorrow,” said John M. Greally, one of the authors and an epigenetics expert at the Albert Einstein College of Medicine in New York. © 2016 The New York Times Company