Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases
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Roger Dobson Older male nightingales have perfected an art that would be the envy of men having a mid-life crisis: a trick that makes them more attractive to females than their younger male competitors. Their mastery of successful courtship is achieved with a dazzling array of up to 100 trills a second, far more than their younger competitors can manage, and more than any other investigated bird, according to new research. That ability, backed up by a sophisticated playlist of about 200 songs, means that they are probably seen as better mates by young trill-seeking females. Singing so many trills at peak frequency requires a lot of physical effort and, as a result, it has evolved as a sign on fitness, say the researchers. "Females could assess the age of the male singer by the trill rate, and mate preferably with older ones," says the zoologist Dr Valentin Amrhein, who led the study at the University of Basel, Switzerland. "This makes sense for the females because older males have more experience with defending their territory or with raising young, and therefore have a better reproductive performance." The research, being published in the Journal of Avian Biology, shows that older birds can come up with 100 trills a second, making them the fastest singers. They also performed about 200 different song types, but the researchers think it is the immediate impact of the trills that is attracting the females. It would take more than an hour for the male to go through his whole song list. "Since the performance of these sounds is very demanding, the rate at which they can be repeated is limited. Trying to sing rapidly increasing sounds in fast repetition is very hard for us humans as well," says Dr Amrhein. "Singing rapid broadband trills comes at a certain price for the male nightingale, so trilling is a good indicator for mate quality." © independent.co.uk
Autism affects male and female brains differently, a study has suggested. UK experts studied brain scans of 120 men and women, with half of those studied having autism. The differences found in the research, published in journal Brain, show more work is needed to understand how autism affects girls, the scientists say. Experts said girls with the condition could be more stigmatised than boys - and it could be harder for them to be diagnosed at all. Autism affects 1% of the population and is more prevalent in boys, so most research has focused on them. In this study, scientists from the Autism Research Centre at the University of Cambridge used magnetic resonance imaging (MRI) to examine how autism affects the brain of males and females. The study looked at the difference between the brains of typical males and those with autism - and then females with and without autism. They found the brains of females with autism "look" more like - but still not the same as - healthy males, when compared with healthy females. But the same kind of difference was not seen in males with autism - so their brains did not show "extreme" male characteristics. Dr Meng-Chuan Lai, who worked on the study said: "What we have known about autism to date is mainly male-biased. BBC © 2013
// by Jennifer Viegas Single parenting takes on new extremes for certain starfish that are hermaphrodites -- male and female at the same time and, in some cases, self-fertilizing. The species faces high risk of extinction, according to new research. The dire situation faced by the non-mating starfish, Parvulastra parvivipara and Parvulastra vivipara, helps to explain why so many organisms, including humans, have sex. Genetic diversity and the dispersal of youngsters support population growth. The plight of the starfish, documented in the latest issue of the journal Biology Letters, reveals how a life without sex but with self-fertilization could result in eventual oblivion. “There are quite a few reasons why these species are vulnerable,” senior author Michael Hart of Simon Fraser University’s Department of Biological Sciences told Discovery News. “The whole species could be wiped out.” Hart and his team studied the starfish, which are restricted to high intertidal pools of South Australia and Tasmania. These starfish also go by the nickname "sea cushions," since they look a bit more like a cushion than a star when viewed from the side. Most adult starfish of other species do reproduce via a separate male and female. Females usually produce eggs that males fertilize in the seawater. At that point, the fertilized eggs develop and grow before becoming little starfish that will attach themselves to the substrate and start the whole process over again. © 2013 Discovery Communications, LLC.
A gene that affects the brain's dopamine system appears to have influenced mothers' behavior during a recent economic downturn, researchers say. At the beginning of the recession that began in 2007, mothers with the "sensitive" version of a gene called DRD2 became more likely to strike or scream at their children, the researchers say. Mothers with the other "insensitive" version of the gene didn't change their behavior. But once it appeared that the recession would not become a full-fledged depression, the "sensitive" mothers became less likely than "insensitive" mothers to engage in harsh parenting. "You have the same genes, and with a different environment it's a completely different story," says , a professor of contemporary urban problems at Columbia University. "I think that's the most amazing part of what we found." Garfinkel and four other researchers in the Proceedings of the National Academy of Sciences. The surprising finding came about because Garfinkel and the other researchers happened to be studying "fragile" families in 20 large cities when the 2007 recession began. One of the things they were tracking was reports of harsh parenting, including spanking, hitting or screaming at a child, he says. Previous research had found that harsh parenting is more common during economic hard times, so Garfinkel says that's what researchers expected to see during the 2007-2009 period, often called the Great Recession. ©2013 NPR
By Luciana Gravotta Small gains now or big rewards later? The conundrum plagues every decision we make, whether we are investing or dieting. Now researchers find that men and women use different strategies to make such choices. Researchers use gambling games to understand what we do when immediate rewards are pitted against long-term gains. Most of these games find no major differences in how men and women play. An experimental setup called the Iowa Gambling Task (IGT), however, finds consistent—and large—differences between the behavior of men and women: men are better at figuring out the strategy that reaps the bigger payoff. Players are given four decks of cards, and they choose one card at a time from any deck they want. Each card has a win or loss amount on it, and each deck has its own unique payout pattern. Two of the decks contain cards that dole out large or frequent rewards, but consistently choosing cards from these decks leads to losses in the long run. The other two decks provide a modest amount of cash per win but less loss over time, so they offer long-term gains for players who pick from them most frequently. These patterns are carefully obscured so that the winning strategy is not obvious. A review published in February in Behavioural Brain Research finds that men focus on the big picture, watching their total earnings and quickly homing in on which of the decks will lead to gains in the long run. Women focus on details such as the frequencies of wins and losses for each deck, missing the overall impact each deck has on their total balance. Sensitive to losses, women tend to switch to a different deck as soon as they are pinged with a setback, making it more difficult for them to identify the prize deck. © 2013 Scientific American
By CARL ZIMMER “Monogamy is a problem,” said Dieter Lukas of the University of Cambridge in a telephone news conference this week. As Dr. Lukas explained to reporters, he and other biologists consider monogamy an evolutionary puzzle. In 9 percent of all mammal species, males and females will share a common territory for more than one breeding season, and in some cases bond for life. This is a problem — a scientific one — because male mammals could theoretically have more offspring by giving up on monogamy and mating with lots of females. In a new study, Dr. Lukas and his colleague Tim Clutton-Brock suggest that monogamy evolves when females spread out, making it hard for a male to travel around and fend off competing males. On the same day, Kit Opie of University College London and his colleagues published a similar study on primates, which are especially monogamous — males and females bond in over a quarter of primate species. The London scientists came to a different conclusion: that the threat of infanticide leads males to stick with only one female, protecting her from other males. Even with the scientific problem far from resolved, research like this inevitably turns us into narcissists. It’s all well and good to understand why the gray-handed night monkey became monogamous. But we want to know: What does this say about men and women? As with all things concerning the human heart, it’s complicated. © 2013 The New York Times Company
Elizabeth Pollitzer Transplanting muscle-derived stem cells into diseased muscle regenerates it — a phenomenon that holds major potential for human therapies. But for years, researchers were puzzled by the unpredictability of these cells — sometimes they would promote fast regeneration, at other times none at all. Then, in 2007, a group led by Johnny Huard, a stem-cell researcher at the University of Pittsburgh in Pennsylvania, hit on the rather surprising explanation — sex1. Muscle stem cells taken from female mice regenerate new muscle much faster than those from male mice when transplanted into diseased muscle of mice of either sex. Researchers have also found that cells taken from male and female mice respond differently to stress2, and that human cells exhibit wildly different concentrations of many metabolites across the sexes3. Evidence is mounting that cells differ according to sex, irrespective of their history of exposure to sex hormones. These differences could have major implications for the susceptibility to and course of many diseases, their diagnosis and treatment. However, most cell biologists do not note whether the cells they are using come from males or females4. Between 1997 and 2001, ten prescription drugs were withdrawn from the market by the US Food and Drug Administration (FDA), eight of which were more dangerous to women than to men (see go.nature.com/ksindo). The ingredients used in non-prescription drugs can also pose greater health risks to women. In 2000, for instance, the FDA took steps to remove phenylpropanolamine, a component of many over-the-counter medications, from all drug products because of a reported increased risk of bleeding into the brain or into tissue around the brain in women but not in men. Such drug therapies are developed through basic research — but what if sex-related differences in studied cells contribute in a significant way to the observed effects? © 2013 Nature Publishing Group
By Melissa Hogenboom Science reporter, BBC News Male zebra finches that fail to socialise with females during adolescence are less successful at courtship later in life, a study says. This effect mimics the "loser effect" where, after a defeat, an animal is more likely to lose a subsequent fight. Social friendships at a young age were also found to be more important than physical and social attractiveness. The findings are reported in Proceedings of the Royal Society B: Biological Sciences. The loser effect has been well demonstrated in many species, from spiders and fish to birds. After a fight hormonal levels change which negatively affects performance in further fights. Now scientists have found a similar effect for mating. Adolescent males who failed to pair with a juvenile female were later unsuccessful with females they encountered in adulthood. Scientists also paired young males as a control in the experiment. They found that if males failed to pair with another male, it had no effect on their later success. Mylene Mariette, from the University de Saint-Etienne, France, and lead author of the study said: "We know that social interaction is important for some aspects of development, like the role of males to teach youngsters to sing, but so far no study has looked at the effect of how interaction between juveniles affects their behaviour as adults." BBC © 2013
By CARL ZIMMER The golden lion tamarin, a one-pound primate that lives in Brazil, is a stunningly monogamous creature. A male will typically pair with a female and they will stay close for the rest of their lives, mating only with each other and then working together to care for their young. To biologists, this deeply monogamous way of life — found in 9 percent of mammal species — is puzzling. A seemingly better evolutionary strategy for male mammals would be to spend their time looking for other females with which to mate. “Monogamy is a problem,” said Dieter Lukas of the University of Cambridge in a telephone news conference on Monday. “Why should the male keep to one female?” The evolution of monogamy has inspired many different ideas. “These hypotheses have been suggested for the past 40 years, and there’s been no resolution of the debate,” said Kit Opie of the University College London in an interview. On Monday, Dr. Opie and Dr. Lukas each published a large-scale study of monogamy that they hoped would resolve the debate. But they ended up coming to opposing conclusions, which means the debate over monogamy continues. Dr. Lukas, co-author of a paper in the journal Science with Tim Clutton-Brock of Cambridge, looked at 2,545 species of mammals, tracing their mating evolution from their common ancestor some 170 million years ago. The scientists found that mammals shifted from solitary living to monogamy 61 times over their evolution. They then searched for any factors that these mammals had in common. They concluded that monogamy evolves when females become hostile with one another and live in ranges that do not overlap. When females live this way, they set up so much distance between one another that a single male cannot prevent other males from mating with them. Staying close to one female became a better strategy. Once males began doing so, they sometimes evolved to provide care to their offspring as well. © 2013 The New York Times Company
By Susan Milius When a peacock fans out the iridescent splendor of his train, more than half the time the peahen he’s displaying for isn’t even looking at him. That’s the finding of the first eye-tracking study of birds. In more than 200 short clips recorded by eye-tracking cameras, four peahens spent less than one-third of the time actually looking directly at a displaying peacock, says evolutionary biologist Jessica Yorzinski of Purdue University in West Lafayette, Ind. When peahens did bother to watch the shimmering male, they mostly looked at the lower zone of his train feathers. The feathers’ upper zone of ornaments may intrigue human observers, but big eyespots there garnered less than 5 percent of the female’s time, Yorzinski and her colleagues report July 24 in the Journal of Experimental Biology. These data come from a system that coauthor Jason Babcock of Positive Science, an eye-tracking company in New York City, engineered to fit peahens. Small plastic helmets hold two cameras that send information to a backpack of equipment, which wirelessly transmits information to a computer. One infrared head camera focuses on an eye, tracking pupil movements. A second camera points ahead, giving the broad bird’s-eye view. The rig weighs about 25 grams and takes some getting used to. If a peahen with no experience of helmets gets the full rig, Yorzinski says, “she just droops her head to the ground.” Adding bits of technology gradually, however, let Yorzinski accustom peahens to walking around, and even mating, while cameraed up. © Society for Science & the Public 2000 - 2013
by Brian Mustanski, Ph.D. There is a lot of interest in the question of if too much sex, sexual desire, masturbation, or viewing of pornography is an addiction like to alcohol or cocaine. In fact, an early version of the new DSM-V manual of mental disorders included a “hypersexuality” diagnosis, but this diagnosis was not included in the finalized version. One tool to study addiction is to look at how the brain responds to those substances or cues of those substances. Until recently, this neuroscience approach had not been used to study hypersexuality. A new study published in the journal Socioaffective Neuroscience & Psychology has tested the brain’s response to sexual stimuli among a group of individuals who identified as having problems controlling their use of online pornography. This new study was published by my colleague (and fellow Indiana University Psychology alumni) Dr. Nicole Prause, who is an Assistant Research Scientist in the Department of Psychiatry at the University of California- Los Angeles and a Research Scientist at the Mind Research Network. Below are her answers to my questions about this new study. What was the purpose of the study? Some clinicians describe patients who report problems decreasing their sexual behaviors, such as viewing many hours of sexual films online every day, as sexually “addicted” or “hypersexual”. Our study tested whether people who report such problems look like other addicts from their brain responses to sexual images. Studies of drug addictions, such as cocaine, have shown a consistent pattern of brain response to images of the drug of abuse, so we predicted that we should see the same pattern in people who report problems with sex if it was, in fact, an addiction. © Copyright 1991-2013 Sussex Publishers, LLC
An Ontario researcher has discovered that common male crickets talk trash, dance and brag after winning a fight. The discovery has caught the attention of fellow researchers and National Geographic magazine. Lauren Fitzsimmons, a Natural Sciences and Engineering Research Council postdoctoral research fellow at the University of Windsor, discovered the brash behaviour. Fitzsimmons placed pairs of male crickets in a small, clear arena, which always led to fights. The arena included a viewing area for other crickets. She set up three audience situations: a male watching and listening to a fight, a female watching and listening to a fight, or no audience. The combatants bit, pushed and flipped each other around the ring. "After a series of these bouts, one male will kind of sulk away and not interact anymore, while the other will perform a song and dance," Fitzsimmons said. She said the winning cricket would "shake his body back and forth" and chirp in victory. "When we had a male audience watching, the male would produce more of these victory displays," Fitzsimmons said. "The speculation is they can tell there is another individual there, and they’re showing off. "We know females prefer dominant males and males who win fights." © CBC 2013
The lifetime rate of diagnosis of anxiety disorders is higher in women, with 33 percent experiencing an anxiety disorder in their lifetime, as compared with 22 percent of men. Experts believe this difference arises from a combination of hormonal fluctuations, brain chemistry and upbringing: women more often feel responsible for the happiness of others, such as their children or their spouse. © 2013 Scientific American
Oxytocin, the naturally occuring human hormone linked to bonding with a newborn and romantic partner, could also help improve mood after rejection, a laboratory study suggests. When scientists in Montreal gave 100 students either oxytocin or a placebo through a nose spray and then tried to snub them in a conversation, feelings of trust were higher in the hormone group. But the hormone had no effect among those who weren't emotionally charged up by the social rejection of having researchers posing as students disagree, interrupt or ignore them. "Instead of the traditional 'fight or flight' response to social conflict where people get revved up to respond to a challenge or run away from it, oxytocin may promote the 'tend and befriend' response where people reach out to others for support after a stressful event. That can, in turn, strengthen social bonds and may be a healthier way to cope," study author Mark Ellenbogen said in a release. For a decade, researchers have speculated that oxytocin, known as the love hormone, motivates people to seek out social support to respond to challenges and blunt the negative hit of stress. Ellenbogen's team said its study offers the first experimental support of the idea that oxytocin motivates us to strengthen social bonds during times of distress. © CBC 2013
by Helen Fields When a bat moves in for the kill, some moths jiggle their genitals. Researchers made the observation by studying three species of hawk moths—big moths that can hover—in Malaysia. They snared the insects with bright lights, tied tiny leashes around their waists, and let them fly while bat attack sounds played. All three species responded to the noises with ultrasound—which they made by shaking their private parts, the team reports online today in Biology Letters. Males have a structure they use for hanging onto females when they mate; to make the sound, they scrape a patch of large scales on the structure against the very end of their abdomen , letting out two bursts of rapid clicks. Females also make a sound, but the researchers aren't sure how. The scientists don't know exactly what the sounds are for, either. The noise may warn the bats that they're trying to mess with a fast-moving, hard-to-catch piece of prey, or it might jam the bat's ultrasound signals. Either way, the racy display may save their lives. © 2010 American Association for the Advancement of Science
Should I stay or should I go? Well, how much food do you have? In some organisms, sexual desire is expressed by leaving, that is, by bidding adieu to a delicious pile of food and wandering off in search of a mate. But not just any mate, a mate with food! Lipton et al., at Albert Einstein College of Medicine, use the “leaving assay” to measure male sexual desire. Their subject is the elegant, rod-like worm, Caenorhabditis elegans.* They start by placing males on their preferred food source; then they measure how often males exit in search of mating partners. You can see the trails they leave in the substrate in this video of C. elegans appropriating Harlem art and culture. How do the researchers know “leaving” is a sex behavior? Context. Leaving a food source occurs only in a sexual context, and the leaving assay is being used to tease apart the threads that control the appetites for food and sex. First, a quick lesson in the fascinating sexuality of C. elegans. Males are not interested in other males, but they search intensely for a mating partner of the other sex. Note that I said “other sex” not “opposite sex.” There are no female C. elegans. Males of this species mate enthusiastically with hermaphrodites. Hermaphrodites can, of course, self-fertilize, but sexual unions between males and hermaphrodites are far more fruitful than selfing. For hermaphrodites, mating with a male will produce more offspring, and for males, hermaphrodites are the only crying game in town.
Keyword: Sexual Behavior
Link ID: 18341 - Posted: 07.03.2013
By Scicurious Sometimes, funny stories really bring out the wonder of the human body. You can get orgasms triggered in your feet, because of overlap in the sensory cortex. Receptors that are involved in narcolepsy are also involved in how much you eat. And knocking out receptors that regulate taste…can make you sterile? Who knew? Let’s start with taste. We taste because the chemicals in foods hit receptors on our tongues. Receptors for sweet, salt, bitter, sour, and umami (which can commonly be thought of as “savory”). Now, a receptor isn’t just a single protein, it’s actually several protein subunits working together to function. So, for example, the receptor subunit TAS1R3 is a subunit that can play two different tasting roles. When combined with one other subunit, it helps to sense sweet (like saccharin), and when combined with another, if helps you taste umami (like MSG, which is definitely umami flavored). If you get rid of the gene for TAS1R3, you end up with an animal that can’t detect either sweet or umami very well. There’s another subunit that is covered in this paper as well, GNAT3. GNAT3, instead of being specific for something like sweet or bitter, instead plays a role in “basic taste“. But these two protein subunits are not JUST expressed on the tongue and in the gastrointestinal tract. They are expressed elsewhere in the body…and especially in the testicles. © 2013 Scientific American
By Carrie Arnold We all experience the occasional life-changing event—a new baby, a cross-country move, a serious injury. In rare cases, such events can precipitate a mental disorder. The problem is compounded because people often assume their suffering is par for the course after such upheaval. In reality, relief is probably a short treatment away, via therapy or medication. For a new mother, dealing with a newborn is fraught with anxieties. Did I fasten the car seat properly? Is the baby still breathing? In more than one in 10 new mothers, these normal worries can escalate into more serious obsessions that can interfere with her ability to care for herself and her baby. Most of the research on postpartum psychiatric problems has focused on depression and psychosis. Obstetricians such as Emily Miller of Northwestern University, however, were also noticing a range of anxiety-related disorders, including intrusive thoughts and repetitive behaviors. “It's good to check that your baby is strapped into the car seat,” Miller notes. “But these women aren't just doing it once. They're doing it over and over, and it's interfering with their lives.” With her colleagues, Miller followed 461 women after they gave birth. Eleven percent said they had obsessions and compulsions two weeks after delivery that the researchers found to be the equivalent of mild to moderate obsessive-compulsive disorder (OCD)—a sharp increase over the 2 to 3 percent rate of OCD in the general population. Half of these women's symptoms continued six months' postpartum, and an additional 5.4 percent developed new OCD symptoms in that time. The afflicted women indicated that their symptoms were distressing, taking up a significant amount of time and otherwise interfering with their daily life. © 2013 Scientific American
A randomized clinical trial of estrogen therapy in younger postmenopausal women, aged 50–55, has found no long-term risk or benefit to cognitive function. The National Institutes of Health-supported study, reported in JAMA Internal Medicine on June 24, 2013, looked at women taking conjugated equine estrogens, the most common type of postmenopausal hormone therapy in the United States. The earlier Women’s Health Initiative Memory Study (WHIMS) linked the same type of hormone therapy to cognitive decline and dementia in older postmenopausal women. The new findings come from the Women’s Health Initiative Memory Study of Younger Women (WHIMSY) trial and were reported by Mark A. Espeland, Ph.D., Wake Forest School of Medicine, Winston-Salem, N.C., on behalf of the academic research centers involved in the study. The study was funded primarily by the National Institute on Aging (NIA), along with the National Heart, Lung, and Blood Institute (NHLBI), both components of the NIH. “The WHIMS study found that estrogen-based postmenopausal hormone therapy produced deficits in cognitive function and increased risk for dementia when prescribed to women 65 and older,” said NIA Director Richard J. Hodes, M.D. “Researchers leading the WHIMSY study wanted to expand on those results by exploring the possibility of a window of opportunity whereby hormone therapy might promote or preserve brain health when given to younger women.” “In contrast to findings in older postmenopausal women, this study tells women that taking these types of estrogen-based hormone therapies for a relatively short period of time in their early postmenopausal years may not put them at increased risk for cognitive decline over the long term,” said Susan Resnick, Ph.D., chief of the Laboratory of Behavioral Neuroscience, in NIA’s Intramural Research Program and a co-author of the study. “Further, it is important to note that we did not find any cognitive benefit after long-term follow-up.”
by Traci Watson For the male dark fishing spider, the price of love is death. New research shows that the male Dolomedes tenebrosus (right) expires just after the height of passion, despite no visible assault by his partner. Scientists collected the common U.S. arachnids (see image) in Nebraska parks and did a little matchmaking. In 25 observed matings, after the male stuffed his sperm into the female's body using his antennalike pedipalp, he immediately went limp and his legs curled underneath him, researchers report online today in Biology Letters. By counting the pulse rate in the spiders' abdomens, researchers measured the heartbeat of motionless males and confirmed that they do indeed die. As if death weren't sacrifice enough, the scientists found that lovemaking also disfigures the male. In most spiders, part of the male's pedipalp swells to deliver sperm before shrinking to normal size. In D. tenebrosus, the pedipalp remains enormously enlarged and presumably useless even after the deed is done. Evolutionary theory predicts male monogamy—such as that shown by the dark fishing spider—when females are larger than males. Smaller animals are more likely to survive to mating age than big ones, the thinking goes, making larger females scarcer than smaller males. And that means males must settle for just one inamorata. True to theory, the female dark fishing spider, whose outstretched legs span a human's palm, outweighs her man 14-to-1. © 2010 American Association for the Advancement of Science