Chapter 8. Hormones and Sex
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By Susan Chenelle and Audrey Fisch “Lord of the Flies” has been a classroom staple for decades, perhaps because the issues of bullying and male aggression remain central concerns in the lives of adolescents, even if they aren’t stranded on a desert island. “To Study Aggression, a Fight Club for Flies” zeros in on the issue of male aggression, but in fruit flies, rather than humans. The connections, beyond the titular, are tantalizing. James Gorman, the science reporter, is focused on research about the neuropeptide tachykinin, produced in the brains of male fruit flies only. When researchers manipulated the neurons, they could decrease aggression in the flies. What does this suggest about the neuroscience of aggression? And what is the relationship between aggression and gender? Below, we match Mr. Gorman’s article with a passage from Chapter 8 of “Lord of the Flies” in which Jack leads his peers in the hunt of a sow. At this point in the novel, Jack has overthrown Ralph and Piggy’s attempts to establish order and civility among the boys. Jack has won over a majority of the boys, and in this scene the group engages in a collective hunt for food that transforms itself into a kind of orgy of male violence. The gender politics of the scene are striking: The attack on the mother pig calls out for careful analysis. The boys are, for example, “wedded to her in lust” and climactically “heavy and fulfilled upon her” at the moment of her killing. What point is William Golding trying to make, here and elsewhere in the novel, about the nature of these young men and the ways in which they turn to and relish in aggression and violence? Key Question: What is the relationship between aggression and gender? © 2015 The New York Times Company
By David Shultz The most venomous animal on the planet isn’t a snake, a spider, or a scorpion; it’s a snail—a cone snail, to be precise. The Conus genus boasts a large variety of marine snails that have adopted an equally diverse assortment of venoms. Online today in the Proceedings of the National Academy of Sciences, researchers report an especially interesting addition to the animals’ arsenal: insulin. According to the paper, this marks the first time insulin has been discovered as a component of venom. Not all cone snails incorporate insulin into their venom cocktail, wonderfully known as nirvana cabal; the hormone was found only in a subset of the animals that hunt with a netting strategy that relies on snaring fish in their large, gaping mouthparts. Unlike the feeding tactics of some cone snails that hunt using speedy venom-tipped “harpoons,” the mouth-netting strategy is a rather slow process. For it to work, the fish either needs to be very unaware of its surroundings or chemically sedated. Scientists speculate that it’s the insulin that provides such sedation. Snails like Conus geographus (seen above) actually produce multiple variants of the hormone, some of which, like one called Con-Ins G1, are more similar to fish insulin than snail varieties. Con-Ins G1 isn’t an exact match of fish insulin though; it’s a stripped-down version that the team suspects may be missing bits that would let fish detect the overdose and respond. If they’re correct, the snail’s venom may yield insight into the nuances of how insulin is regulated that may extend to humans. © 2015 American Association for the Advancement of Science
Helen Fisher, a biological anthropologist at Rutgers University responds: Several years ago I embarked on a project to see if the seven-year itch really exists. I began by studying worldwide data on marriage and divorce and noticed that although the median duration of marriage was seven years, of the couples who divorced, most did so around their fourth year together (the “mode”). I also found that divorce occurred most frequently among couples at the height of their reproductive and parenting years—for men, ages 25 to 29, and for women, ages 20 to 24 and 25 to 29—and among those with one dependent child. To try to explain these findings, I began looking at patterns of pair bonding in birds and mammals. Although only about 3 percent of mammals form a monogamous bond to rear their young, about 90 percent of avian species team up. The reason: the individual that sits on the eggs until they hatch will starve unless fed by a mate. A few mammals are in the same predicament. Take the female fox: the vixen produces very thin milk and must feed her young almost constantly, so she relies on her partner to bring her food while she stays in the den to nurse. But here's the key: although some species of birds and mammals bond for life, more often they stay together only long enough to rear their young through infancy and early toddlerhood. When juvenile robins fly away from the nest or maturing foxes leave the den for the last time, their parents part ways as well. Humans retain traces of this natural reproductive pattern. In more contemporary hunter-gatherer societies, women tend to bear their children about four years apart. Moreover, in these societies after a child is weaned at around age four, the child often joins a playgroup and is cared for by older siblings and relatives. This care structure allows unhappy couples to break up and find a more suitable partner with whom to have more young. © 2015 Scientific American
By Neuroskeptic A new study offers two reasons to be cautious about some of the claims made for the role of the hormone oxytocin in human behavior. The paper’s out now in PLoS ONE from researchers James C. Christensen and colleagues, who are based at the US Air Force Research Laboratory in Ohio. That the military are interested in oxytocin at all is perhaps a testament to the huge amount of interest that this molecule has attracted in recent years. Oxytocin has been called the “hug hormone”, and is said to be involved in such nice things as love and trust. But according to Christensen et al., quite a lot of previous oxytocin research may be flawed. Their paper is in two parts. Christensen et al. first show that the only accurate way to measure oxytocin levels in blood is by performing plasma extraction before chemical analysis. Using unextracted plasma, they find, leads to seriously distorted measures. The differences between extracted and unextracted plasma estimates of oxytocin have been noted before, but Christensen et al. show directly that unextracted plasma interferes with oxytocin measurement. They found that oxytocin test kits were unable to detect a ‘spike’ of pure oxytocin added to some unextracted plasma samples, whereas the spike was reliably detected when added to an extracted sample. This was true using either the ELISA or RIA method for quantification of oxytocin. With ELISA, unextracted oxytocin measures were also very noisy and unrealistically high:
Keyword: Hormones & Behavior
Link ID: 20479 - Posted: 01.14.2015
By DOUGLAS QUENQUA A sparrow’s song may sound simple, consisting of little more than whistles and trills. But to the sparrows, those few noises can take on vastly different meanings depending on small variations in context and repetition, researchers have found. In humans, the ability to extract nearly endless meanings from a finite number of sounds, known as partial phonemic overlapping, was key to the development of language. To see whether sparrows shared this ability, researchers at Duke University recorded and analyzed the songs of more than 200 Pennsylvania swamp sparrows. They found that the sparrows’ whistles could be divided into three lengths: short, intermediate and long. The researchers then played the sparrows two versions of the songs — the original and a slightly altered one. They found that replacing a single short whistle with an intermediate one, for example, could significantly alter a bird’s reaction, but only if it came at the right moment in the song. “Identical sounds seemed to belong to a different category depending on the context,” said Robert F. Lachlan, a biologist now with Queen Mary University of London and the lead author of the study. The findings, which were published in Proceedings of the National Academy of Sciences, are part of a larger effort to better understand how human language evolved. If even birds rely on phonemic overlapping to communicate, Dr. Lachlan said, it could indicate that such features “developed independently of higher aspects of language.” © 2015 The New York Times Company
ByDavid Malakoff This bird might look like a holiday ornament, but it is actually a rare half-female, half-male northern cardinal (Cardinalis cardinalis, pictured with female plumage on the left and male plumage on the right) spotted a few years ago in Rock Island, Illinois. Researchers have long known such split-sex “gynandromorphs” exist in insects, crustaceans, and birds. But scientists rarely get to extensively study a gynandromorph in the wild; most published observations cover just a day or so. Observers got to follow this bird, however, for more than 40 days between December 2008 and March 2010. They documented how it interacted with other birds and even how it responded to recorded calls. The results suggest being half-and-half carries consequences: The cardinal didn’t appear to have a mate, and observers never heard it sing, the researchers report this month in The Wilson Journal of Ornithology. On the other hand, it wasn’t “subjected to any unusual agonistic behaviors from other cardinals,” according to the paper. Intriguingly, another gynandromorph cardinal sighted briefly in 1969 had the opposite plumage, they note: the male’s bright red plumes on the right, the drabber female feathers on the left. © 2014 American Association for the Advancement of Science
Keyword: Sexual Behavior
Link ID: 20442 - Posted: 12.27.2014
By Sandhya Sekar A well-fed female mantis is irresistible to a male. She’s chock-full of eggs and draws him in by producing high levels of pheromones. Now, a new study reveals that starving females can deceive males by enticing them to their doom. Researchers have found that female false garden mantises (Pseudomantis albofimbriata, pictured) that were fed just a quarter of what others got actually produced more pheromones than well-fed females—and attracted almost twice the number of males. This is despite the fact that the number of eggs in the starved females was less than 10, compared with more than 60 eggs in well-fed females. The finding, reported online today in the Proceedings of the Royal Society B, is the first experimental demonstration of sexual deception using false chemical signals in any animal. The starving females seem to be treating the males as easy prey to gain nutritional benefits and potentially produce more eggs. © 2014 American Association for the Advancement of Science
Katie Langin In the first couple of years after birth, sea lion sons seem to be more reliant on their mothers—consuming more milk and sticking closer to home—than sea lion daughters are, according to a study on Galápagos sea lions published in the December issue of the journal Animal Behaviour. The young males venture out to sea on occasion, but their female counterparts dive for their own food much more often. The curious thing is, it's not like the young males aren't capable of diving. As one-year-olds, males can dive to the same depth as females (33 feet, or 10 meters, on a typical dive). It's also not like their mother's milk is always on hand. Sea lion moms frequently leave their growing offspring for days at a time to find food at sea. (Watch a video of a Galápagos sea lion giving birth.) And yet, despite all this, for some reason sons are far less likely than daughters to take to the sea and seek out their own food. "We always saw the [young] males around the colony surfing in tide pools, pulling the tails of marine iguanas, resting, sleeping," said Paolo Piedrahita, a Ph.D. student at Bielefeld University in Germany and the lead author of the study. "It's amazing. You can see an animal—40 kilograms [88 pounds]—just resting, waiting for mom." © 1996-2014 National Geographic Society.
By Pippa Stephens Health reporter, BBC News Women are more likely than men to display symptoms of depression when in a position of authority at work, according to US scientists. In men, authority, such as the ability to hire and fire people, decreases depressive symptoms, the study said. The study, published in the Journal of Health and Social Behaviour, looked at 2,800 middle-aged men and women. One expert said the study showed the need for more women in authority and more varied female role models. Scientists at the University of Texas at Austin interviewed 1,300 male and 1,500 female graduates from Wisconsin high schools over the phone in 1993 and 2004, when they were aged about 54 and 64. Researchers asked participants about job authority and about the number of days in the past week they felt depressive symptoms, such as feeling sad and thinking one's life is a failure. When the job included hiring, firing and influencing pay, women were predicted to have a 9% increased rate of depressive symptoms than women without authority. Meanwhile, men had a 10% decreased rate of depressive symptoms. The study said it controlled for other factors that could cause depression, such as hours worked per week, whether people had flexible hours and how often workers were checked by a supervisor. Scientists also said men were more likely to decide when to start and finish work than women and were less frequently monitored by their advisers. Lead researcher Tetyana Pudrovska said: "These women have more education, higher incomes, more prestigious occupations, and higher levels of job satisfaction and autonomy than women without job authority. Yet they have worse mental health than lower status women." BBC © 2014
By Bethany Brookshire WASHINGTON — Estrogen can protect the brain from harmful inflammation following traumatic injury, a new study in zebra finches suggests. Boosting levels of the sex hormone in the brain might help prevent the cell loss that occurs following damage from injuries such as stroke. Estrogen levels quadrupled around the damaged area in both male and female zebra finches after researchers gave them experimental brain injuries, Colin Saldanha and colleagues at American University in Washington, D.C., reported November 17 at the annual meeting of the Society for Neuroscience. When the scientists prevented finch brains from making estrogen, inflammatory proteins at damaged sites increased. The helpful estrogen didn’t come from gonads. It’s made within the brain by support cells called astrocytes close to the injury. Injury inflames the brain. Initially, this inflammation recruits helpful cells to the damaged area and aids in recovery. But the long-term presence of inflammatory proteins can cause harm, killing off brain cells and reducing functions such as movement and memory. The researchers hope that by understanding how estrogen reduces inflammatory proteins, therapies might boost this natural estrogen production to keep harmful inflammation at bay. © Society for Science & the Public 2000 - 2014.
By Elahe Izadi Putting very little babies through numerous medical procedures is especially challenging for physicians, in part because reducing the pain they experience is so difficult. Typically for patients, "the preferred method of reducing pain is opiates. Obviously you don't want to give opiates to babies," says neurologist Regina Sullivan of NYU Langone Medical Center. "Also, it's difficult to know when a baby is in pain and not in pain." In recent years, research has shown environmental factors, like a mother or caregiver having contact with a baby during a painful procedure, appears to reduce the amount of pain felt by the baby, at least as indicated by the child's behavior, Sullivan said. But she and Gordon Barr of the University of Pennsylvania, an expert in pain, were interested in whether a mother's presence actually changed the brain functioning of a baby in pain. So Sullivan and Barr turned to rats. Specifically mama and baby rats who were in pain. And they found that hundreds of genes in baby rats' brains were more or less active, depending on whether the mothers were present. Sullivan and Barr presented their committee peer-reviewed research before the Society for Neuroscience annual meeting Tuesday. They gave mild electric shocks to infant rats, some of which had their mothers around and others who didn't. The researchers analyzed a specific portion of the infants' brains, the amygdala region of neurons, which is where emotions like fear are processed.
By Kelly Servick Dean Hamer finally feels vindicated. More than 20 years ago, in a study that triggered both scientific and cultural controversy, the molecular biologist offered the first direct evidence of a “gay gene,” by identifying a stretch on the X chromosome likely associated with homosexuality. But several subsequent studies called his finding into question. Now the largest independent replication effort so far, looking at 409 pairs of gay brothers, fingers the same region on the X. “When you first find something out of the entire genome, you’re always wondering if it was just by chance,” says Hamer, who asserts that new research “clarifies the matter absolutely.” But not everyone finds the results convincing. And the kind of DNA analysis used, known as a genetic linkage study, has largely been superseded by other techniques. Due to the limitations of this approach, the new work also fails to provide what behavioral geneticists really crave: specific genes that might underlie homosexuality. Few scientists have ventured into this line of research. When the genetics of being gay comes up at scientific meetings, “sometimes even behavioral geneticists kind of wrinkle up their noses,” says Kenneth Kendler, a psychiatric geneticist at Virginia Commonwealth University in Richmond. That’s partially because the science itself is so complex. Studies comparing identical and fraternal twins suggest there is some heritable component to homosexuality, but no one believes that a single gene or genes can make a person gay. Any genetic predispositions probably interact with environmental factors that influence development of a sexual orientation. © 2014 American Association for the Advancement of Science.
Carl Zimmer In the early 1970s, Sarah Blaffer Hrdy, then a graduate student at Harvard, traveled to India to study Hanuman langurs, monkeys that live in troops, each made up of several females and a male. From time to time, Dr. Hrdy observed a male invade a troop, driving off the patriarch. And sometimes the new male performed a particularly disturbing act of violence. He attacked the troop’s infants. There had been earlier reports of infanticide by adult male mammals, but scientists mostly dismissed the behavior as an unimportant pathology. But in 1974, Dr. Hrdy made a provocative counter proposal: infanticide, she said, is the product of mammalian evolution. By killing off babies of other fathers, a male improves his chances of having more of his own offspring. Dr. Hrdy went on to become a professor at the University of California, Davis, and over the years she broadened her analysis, arguing that infanticide might well be a common feature of mammalian life. She spurred generations of scientists to document the behavior in hundreds of species. “She’s the goddess of all this stuff,” said Kit Opie, a primatologist at University College London. Forty years after Dr. Hrdy’s initial proposal, two evolutionary biologists at the University of Cambridge have surveyed the evolution of infanticide across all mammals. In a paper published Thursday in Science, the scientists concluded that only certain conditions favor the evolution of infanticide — the conditions that Dr. Hrdy had originally proposed. “My main comment is, ‘Well done,'” said Dr. Hrdy. She said the study was particularly noteworthy for its scope, ranging from opossum to lions. The authors of the new study, Dieter Lukas and Elise Huchard, started by plowing through the scientific literature, looking for evidence of infanticide in a variety of mammalian species. The researchers ended up with data on 260 species, and in 119 of them — over 45 percent — males had been observed killing unrelated young animals. © 2014 The New York Times Company
Carl Zimmer Milk is not just food. The more closely scientists examine it, the more complexity they find. Along with nutrients like protein and calcium, milk contains immune factors that protect infants from disease. It hosts a menagerie of microbes, too, some of which may colonize the guts of babies and help them digest food. Milk even contains a special sugar that can fertilize that microbial garden. Now, it turns out, milk also contains messages. A new study of monkeys, published in the journal Behavioral Ecology, demonstrates that a hormone present in milk, cortisol, can have profound effects on how babies develop. Infant monkeys rely on cortisol to detect the condition of their mothers, the authors suggest, then adjust their growth and even shift their temperaments. Jeffrey French, a neuroendocrinologist at the University of Nebraska at Omaha who was not involved in the study, praised its “remarkable sophistication” and said that it helped to change how we think about breast milk. “Milk serves almost like a pheromone, a chemical signal sent from one individual to another,” he said. Katie Hinde, a behavioral biologist at Harvard and lead author on the new study, and her colleagues studied 108 rhesus macaque mothers nursing infants at the California National Primate Research Center. The researchers collected samples of milk, measuring how much energy each provided and the cortisol it contained. Dr. Hinde and her colleagues also measured how much weight each nursing monkey gained and tracked its behavior. Cortisol serves many functions in mammals, but it is best known as a stress hormone. When cortisol courses through our bodies, it prepares us to handle alarming or fearful situations, increasing the brain’s consumption of glucose and suppressing the digestive system. © 2014 The New York Times Company
by Catherine Brahic Once described as the finest sound in nature, the song of the North American hermit thrush has long captivated the human ear. For centuries, birdwatchers have compared it to human music – and it turns out they were on to something. The bird's song is beautifully described by the same maths that underlies human harmonies. To our ears, two notes usually sound harmonious together if they follow a set mathematical relationship. An octave is a doubling of frequencies. Tripling the frequency of sound produces a perfect fifth, quadrupling is yet another octave, and quintupling produces a perfect third. These relationships define the most common major chords – the ones that, across human cultures, we tend to find most pleasant to listen to. Early studies sought to determine whether these mathematical relationships also governed the notes in bird song. Studies in the white-throated sparrow and the northern nightingale-wren failed to find the same musical intervals as those used in human music, and deemed birdsong to be something different entirely. Making tweet music The song of the hermit thrush challenges that conclusion. Tecumseh Fitch of the University of Vienna in Austria and colleagues analysed recordings taken in the wild of 70 full songs from this species. They isolated the frequencies corresponding to each note, and calculated the relationships between pitches appearing in each song. Lo and behold, the vast majority of songs used notes that fitted the same simple mathematical ratios as human harmony. What's more, Fitch says the thrush can produce other notes - meaning it must choose to use these harmonic chords. © Copyright Reed Business Information Ltd.
Joan Raymond TODAY contributor It’s well established that baby talk plays a huge role in helping the wee widdle babies learn to tawk. And — no surprise — moms talk more to babies than dads do. But it seems that the baby's sex plays a role, too: Moms may be talking more to their infant daughters than their sons during the early weeks and months of a child’s life. In a new study published Monday in the online edition of Pediatrics, researchers looked at the language interactions between 33 late preterm and term infants and their parents by capturing 3,000 hours of recordings. Somewhat surprisingly, the researchers found that moms interacted vocally more with infant daughters rather than sons both at birth and 44 weeks post-menstrual age (equivalent to 1 month old.) Male adults responded more frequently to infant boys than infant girls, but the difference did not reach statistical significance, say the researchers. “We wanted to look more at gender and factors that affect these essentially mini-conversations that parents have with infants,” says lead author and neonatologist Dr. Betty Vohr, director of the Neonatal Follow-Up Program at Women & Infants Hospital of Rhode Island. “Infants are primed to vocalize and have reciprocal interactions.”
by Bethany Brookshire In many scientific fields, the study of the body is the study of boys. In neuroscience, for example, studies in male rats, mice, monkeys and other mammals outnumber studies in females 5.5 to 1. When scientists are hunting for clues, treatments or cures for a human population that is around 50 percent female, this boys-only club may miss important questions about how the other half lives. So in an effort to reduce this sex bias in biomedical studies, National Institutes of Health director Francis Collins and Office of Research on Women’s Health director Janine Clayton announced in May a new policy that will roll out practices promoting sex parity in research, beginning with a requirement that scientists state whether males, females or both were used in experiments, and moving on to mandate that both males and females are included in all future funded research. The end goal will be to make sure that NIH-funded scientists “balance male and female cells and animals in preclinical studies in all future [grant] applications” to the NIH. In 1993, the NIH Revitalization Act mandated the inclusion of women and minorities in clinical trials. This latest move extends that inclusion to cells and animals in preclinical research. Because NIH funds the work of morethan 300,000 researchers in the United States and other countries, many of whom work on preclinical and basic biomedical science, the new policy has broad implications for the biomedical research community. And while some scientists are pleased with the effort, others are worried that the mandate is ill-conceived and underfunded. In the end, whether it succeeds or fails comes down to interpretation and future implementation. © Society for Science & the Public 2000 - 2014
By David Bornstein Shortly after the birth of her daughter, Andrea became severely depressed. She was 17 at the time and she didn’t fully understand what she was going through; she just felt like a failure. “I felt like I didn’t want to be alive,” she recalls. “I felt like I didn’t deserve to be alive. I felt like a bad person and a bad mother, and I was never going to get any better.” When her baby persisted in crying, she felt her frustration mount quickly. “I was hitting a boiling point,” she says. “I was at a point where I didn’t want to deal with anything. Sometimes I would just let her cry — but then I would feel very bad afterwards.” Depression is the most common health problem women face. In the United States, outside of obstetrics, it is the leading cause of hospitalizations among women ages 15 to 44. It’s estimated that 20 percent to 25 percent of women will experience depression during their lifetimes, and about one in seven will experience postpartum depression. For low-income women, the rates are about twice as high. As my colleague Tina Rosenberg has reported, the World Health Organization ranks depression as the most burdensome of all health conditions affecting women (as measured by lost years of productive life). Postpartum depressions are often assumed to be associated with hormonal changes in women. In fact, only a small fraction of them are hormonally based, said Cindy-Lee Dennis, a professor at the University of Toronto and a senior scientist at Women’s College Research Institute, who holds a Canada Research Chair in Perinatal Community Health. The misconception is itself a major obstacle, she adds. Postpartum depression is often not an isolated form of depression; nor is it typical. “We now consider depression to be a chronic condition,” Dennis says. “It reoccurs in approximately 30 to 50 percent of individuals. And a significant proportion of postpartum depression starts during the pregnancy but is not detected or treated to remission. We need to identify symptoms as early as possible, ideally long before birth.” © 2014 The New York Times Company
Daniel Cressey The history of sex may have to be rewritten thanks to a group of unsightly, long-extinct fish called placoderms. A careful study1 of fossils of these armour-plated creatures, which gave rise to all current vertebrates with jaws, suggests that their descendants — our ancient ancestors — switched their sexual practices from internal to external fertilization, an event previously thought to be evolutionarily improbable. “This was totally unexpected,” says John Long, a palaeontologist at Flinders University in Adelaide, Australia, and lead author of the study, published in Nature1. “Biologists thought that there could not be a reversion back from internal fertilization to external fertilization, but we have shown it must have happened this way.” Go back far enough in your family tree — before placoderms — and your ancestors were rather ugly jawless fish who reproduced through external fertilization, in which sperm and eggs are expelled into the water to unite. Some of these distant relatives later gave rise to the jawless fish called lampreys that lurk in seas today and still use this method of reproduction. Bony organ Long's team studied placoderms, one of the earliest groups of jawed animals, and found structures in fossils that they interpret as bony ‘claspers’ — male organs that penetrate the female and deliver sperm. © 2014 Nature Publishing Group,
Clare Pain Eating a high fat and high carb diet resulted in inflammation in the brain - at least in male mice. We'll have to wait to see if the same process applies to male humans. The detrimental impact of junk food seems to be connected to inflammation in the brains of male mice, with the brains of females protected by oestrogen, according to research published today in Cell Reports. Dr Deborah Clegg, who led the study while at University of Texas Southwestern Medical Centre, Dallas, USA, was building on existing research that links brain inflammation with obesity and heart disease in male mice. "We embarked on this research because [the link with inflammation] had been shown in male mice, so we asked ourselves, do the same processes occur in females?" explains Clegg. Previous research has shown that one cause of inflammation in the hypothalamus - the part of the brain that controls energy balance - is palmitic acid, a saturated fatty acid found in palm oil, dairy products and meat, and common in high fat food. The team looked at male and female mice, fed either their normal diet or a 'high fat' diet. Besides containing 42 per cent fat, the high fat diet was also high in carbohydrates making it a good correlate of human junk food, says Clegg. © 2014 ABC