Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases

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Jon Hamilton Professional fighter Gina Mazany practices during a training session at Xtreme Couture Mixed Martial Arts in Las Vegas. She well remembers her first concussion — which came in her first fight. "I was throwing up that night, Mazany says. Bridget Bennett for NPR Gina Mazany grew up in Anchorage, Alaska. And that's where she had her first fight. "It was right after I turned 18," she recalls. A local bar had a boxing ring, and Mazany decided to give it a shot. Her opponent was an older woman with a "mom haircut." "She beat the crap out of me," Mazany says. "Like she didn't knock me out, she didn't finish me. But she just knocked me around for three rounds. And I remember, later that night I was very, very nauseous. I was throwing up that night." It was her first concussion. Concussions are just part of her sport, Mazany figures, but says she tries to protect herself, and to not give anyone else a head injury--at least in training. Bridget Bennett for NPR Thanks to research on boxers and football players, both athletes and the public are becoming more aware of the dangers of sports-related head injuries. Yet there is little data on participants like Mazany. That's because, unlike the vast majority of athletes studied, she is a woman. "We classically have always known the male response to brain injury," says Mark Burns, at Georgetown University. But there have been remarkably few studies of females. The bias runs throughout the scientific literature, even in studies of mice. © 2017 npr

Keyword: Brain Injury/Concussion
Link ID: 23865 - Posted: 07.24.2017

by Laurel Hamers The tempo of a male elephant seal’s call broadcasts his identity to rival males, a new study finds. Every male elephant seal has a distinct vocalization that sounds something like a sputtering lawnmower — pulses of sound in a pattern and at a pace that stays the same over time. At a California state park where elephant seals breed each year, researchers played different variations of an alpha male’s threat call to subordinate males who knew him. The seals weren’t as responsive when the tempo of that call was modified substantially, suggesting they didn’t recognize it as a threat. Modifying the call’s timbre — the acoustic quality of the sound — had the same effect, researchers report August 7 in Current Biology. Unlike dolphins and songbirds, elephant seals don’t seem to vary pitch to communicate. Those vocal name tags serve a purpose. During breeding season, male elephant seals spend three months on land without food or water, competing with rivals for social status and mating rights. Fights between two blubbery car-sized animals can be brutal. “We’ve seen males lose their noses,” says Caroline Casey, a biologist at the University of California, Santa Cruz. For lower-ranking males, identifying an alpha male by his call and then backing off might prevent a beach brawl. |© Society for Science & the Public 2000 - 2017

Keyword: Animal Communication; Sexual Behavior
Link ID: 23859 - Posted: 07.21.2017

Xiaomeng (Mona) Xu, assistant professor of experimental psychology, and Ariana Tart-Zelvin, If you have experienced the evolution from having a crush to falling in love, it may seem like the transition happens naturally. But have you ever wondered how we make such a huge emotional leap? In other words, what changes take place in our brains that allow us to fall deeply in love? Stephanie Cacioppo, a psychologist at the University of Chicago who has studied the neuroscience of romantic love for the past decade, explains that the process involves several complex changes, particularly in the brain’s reward system. More specifically, in a 2012 review of the love research literature Lisa Diamond and Janna Dickenson, psychologists at the University of Utah, found romantic love is most consistently associated with activity in two brain regions—the ventral tegmental area (VTA) and the caudate nucleus. These areas play an essential role in our reward pathway and regulate the “feel good” neurotransmitter dopamine. In other words, during the early stages of love you crave the person because he or she makes you feel so good. And over time these feelings persist. Our neuroimaging research and that of others suggests that once you are in love—as long as the relationship remains satisfying—simply thinking about your partner not only makes you feel good but can also buffer against pain, stress and other negative feelings. © 2017 Scientific American,

Keyword: Emotions; Sexual Behavior
Link ID: 23852 - Posted: 07.20.2017

Hannah Devlin Science correspondent Brash, brawny and keen to impose their will on anyone who enters their sphere of existence: the alpha male in action is unmistakable. Now scientists claim to have pinpointed the biological root of domineering behaviour. New research has located a brain circuit that, when activated in mice, transformed timid individuals into bold alpha mice that almost always prevailed in aggressive social encounters. In some cases, the social ranking of the subordinate mice soared after the scientists’ intervention, hinting that it might be possible to acquire “alphaness” simply by adopting the appropriate mental attitude. Or as Donald Trump might put it: “My whole life is about winning. I almost never lose.” Prof Hailan Hu, a neuroscientist at Zhejiang University in Hangzhou, China, who led the work said: “We stimulate this brain region and we can make lower ranked mice move up the social ladder.” The brain region, called the dorsal medial prefrontal cortex (dmPFC), was already known to light up during social interactions involving decisions about whether to be assertive or submissive with others. But brain imaging alone could not determine whether the circuit was ultimately controlling how people behave. The latest findings answer the question, showing that when the circuit was artificially switched on, low-ranking mice were immediately emboldened. “It’s not aggressiveness per se,” Hu said. “It increases their perseverance, motivational drive, grit.” © 2017 Guardian News and Media Limited

Keyword: Aggression; Sexual Behavior
Link ID: 23836 - Posted: 07.14.2017

By Giorgia Guglielmi Semen has something in common with the brains of Alzheimer’s sufferers: Both contain bundles of protein filaments called amyloid fibrils. But although amyloid accumulation appears to damage brain cells, these fibrils may be critical for reproduction. A new study suggests that semen fibrils immobilize subpar sperm, ensuring that only the fittest ones make it to the egg. “I’m sure that from the very first time scientists described semen fibrils, they must have been speculating what their natural function was,” says Daniel Otzen, an expert in protein aggregates at Aarhus University in Denmark, who did not participate in the research. “This seems to be the smoking gun.” Researchers discovered semen fibrils in 2007. At first, they seemed like mostly bad news. Scientists showed that the fibrils, found in the seminal fluid together with sperm cells and other components, can bind to HIV, helping it get inside cells. But the fibrils are found in most primates, notes Nadia Roan, a mucosal biologist at the University of California, San Francisco. “If fibrils didn’t serve some beneficial purpose, they would have been eliminated over evolutionary time.” Because the way HIV fuses to cells is reminiscent of the way a sperm fuses to the egg, she wondered whether the fibrils facilitated fertilization. © 2017 American Association for the Advancement of Science.

Keyword: Alzheimers; Sexual Behavior
Link ID: 23828 - Posted: 07.12.2017

By Abby Olena For more than 50 years, scientists have taken for granted that all snakes share a ZW sex determination system, in which males have two Z chromosomes and females have one Z and one W. But a study, published today (July 6) in Current Biology, reveals that the Central American boa (Boa imperator) and the Burmese python (Python bivittatus) use an XY sex determination system, which evolved independently in the two species. “This work is a culmination of a lot of questions that we’ve had about pythons and boas for a long time,” says Jenny Marshall Graves, a geneticist at La Trobe Univeristy in Melbourne, Australia, who did not participate in the study. Some of these questions came up for Warren Booth, a geneticist and ecologist at the University of Tulsa, as he studied parthenogenesis—the growth and development of offspring in the absence of fertilization. He noticed a pattern for organisms undergoing parthenogenesis: animal species that use a ZW system have only male (ZZ) offspring, and the organisms that use an XY system have only female (XX) offspring. Except this pattern doesn’t hold true for boas and pythons, who consistently produce female offspring by parthenogenesis. Booth contacted Tony Gamble, a geneticist at Marquette University in Milwaukee, Wisconsin, who studies sex chromosomes, to begin a collaboration to investigate whether boas and pythons might actually have X and Y chromosomes. Spurred by Booth’s questions, “I went back and reread some of the early papers” on snake sex chromosomes, says Gamble. “What became clear is that they didn’t show that boas and pythons had a ZW sex chromosome system. They just said it without any evidence.” © 1986-2017 The Scientist

Keyword: Sexual Behavior; Evolution
Link ID: 23815 - Posted: 07.09.2017

By Michael Price Male baboons that harass and assault females are more likely to mate with them, according to a new study, adding evidence that sexual intimidation may be a common mating strategy among promiscuous mammals. The study’s authors even argue that the findings could shed light on the evolutionary origins of our own species’ behavior, although others aren’t convinced the results imply anything about people. “I think the data and analyses in this study are first-rate,” says Susan Alberts, a biologist who studies primate behavior at Duke University in Durham, North Carolina. “[But] I also think it’s a big stretch to infer something about the origins of human male aggression towards women.” To conduct the research, Elise Huchard, a zoologist at the National Center for Scientific Research in Montpellier, France, and colleagues examined a group of chacma baboons (Papio ursinus) living in Tsaobis Nature Park in Namibia over a 9-year period. These brownish, dog-sized primates live in troops of dozens of males and females. Females will mate with multiple males throughout the year. The male chacma are about twice the size of females and aggressively fight one another and engage in howling competitions to establish dominance. The more dominant a male is, the more likely he is both to succeed in finding a mate and to sire offspring. Males rarely force females to mate, but after years spent observing the animals in the wild, Huchard noticed that a subtler form of sexual coercion appeared to be going on. “Males often chase and attack some females of their own group when meeting another group, and they generally target sexually receptive females on such occasions,” she says. “I spent a great deal of time studying female mate choice, and my main impression … was that females don't have much room to express any preference.” © 2017 American Association for the Advancement of Science

Keyword: Sexual Behavior; Aggression
Link ID: 23813 - Posted: 07.07.2017

By STEPH YIN Whales and songbirds produce sounds resembling human music, and chimpanzees and crows use tools. But only one nonhuman animal is known to marry these two skills. Palm cockatoos from northern Australia modify sticks and pods and use them to drum regular rhythms, according to new research published in Science Advances on Wednesday. In most cases, males drop beats in the presence of females, suggesting they perform the skill to show off to mates. The birds even have their own signature cadences, not unlike human musicians. This example is “the closest we have so far to musical instrument use and rhythm in humans,” said Robert Heinsohn, a professor of evolutionary and conservation biology at the Australian National University and an author of the paper. A palm cockatoo drumming performance starts with instrument fashioning — an opportunity to show off beak strength and cleverness (the birds are incredibly intelligent). Often, as a female is watching, a male will ostentatiously break a hefty stick off a tree and trim it to about the length of a pencil. Holding the stick, or occasionally a hard seedpod, with his left foot (parrots are typically left-footed), the male taps a beat on his tree perch. Occasionally he mixes in a whistle or other sounds from an impressive repertoire of around 20 syllables. As he grows more aroused, the crest feathers on his head become erect. Spreading his wings, he pirouettes and bobs his head deeply, like an expressive pianist. He uncovers his red cheek patches — the only swaths of color on his otherwise black body — and they fill with blood, brightening like a blush. Over seven years, Dr. Heinsohn and his collaborators collected audio and video recordings of 18 male palm cockatoos exhibiting such behaviors in Australia’s Cape York Peninsula, where the birds are considered vulnerable because of aluminum ore mining. © 2017 The New York Times Company

Keyword: Animal Communication; Sexual Behavior
Link ID: 23790 - Posted: 06.29.2017

By Debra W. Soh If there was a way of telling who in our society is sexually attracted to children, are we entitled to know? A recent study from Georg-August-University Göttingen in Germany suggests that we may need to grapple with this question. Phallometric testing, also known as penile plethysmography, is considered the gold standard in measuring male sexual arousal, and particularly, deviant sexual interests such as pedophilia, which is the sexual interest in prepubescent children, roughly aged 3 to 10. The test involves measuring the volume of blood in the test-taker’s penis using an airtight glass tube (or conversely, measuring penile circumference with a mercury strain gauge) while he is presented with a series of images of children and adults, and audio stories describing a corresponding sexual encounter. Phallometry is commonly used in forensic settings to assess the sexual interests of sex offenders, in order to determine their risk of re-offending. As one can imagine, sex offenders tend not to be forthright about their sexual preferences, which makes phallometry all the more important. It has, however, been criticized because the test can become easier for individuals to fool with each successive assessment. Brain scanning using fMRI holds much promise as a diagnostic tool in evaluating sexual interests, as research has documented a reliable network of brain regions involved in sexual arousal. The current study took this another step by testing whether brain functional activation could be used to infer what someone finds sexually interesting without them knowing. © 2017 Scientific American,

Keyword: Sexual Behavior; Brain imaging
Link ID: 23783 - Posted: 06.28.2017

By Alice Klein Women are missing out on optimum medical treatment because most pre-clinical drug research is done in male animals, a new study suggests. New drugs must be evaluated in animals before being considered for human trials. Over three-quarters of these studies use only male animals because of concerns that female hormone cycles will affect experiments. It is also widely assumed that what works for males will work for females. However, research by Natasha Karp at the Wellcome Trust Sanger Institute in Cambridge and her colleagues casts doubt on this assumption. They compared 234 physical traits in 14,000 male and female lab mice. Sex differences were identified for 57 per cent of quantifiable traits – like cholesterol level and bone mass – and for 10 per cent of qualitative traits, like head shape. In another 40,000 mice, they found that when they switched off specific genes, the effects varied according to sex. This suggests that genetic diseases may manifest themselves differently in males and females and require different treatments, says Karp. These sex nuances mean that drugs optimised for male animals may be less effective in females, or even cause harm, says Karp. Between 1997 and 2001, 8 of the 10 drugs that were pulled from the market in the US posed greater health risks for women – possibly as a result of male-biased animal research, she says. © Copyright New Scientist Ltd.

Keyword: Sexual Behavior
Link ID: 23780 - Posted: 06.27.2017

By THERESE HUSTON “Does being over 40 make you feel like half the man you used to be?” Ads like that have led to a surge in the number of men seeking to boost their testosterone. The Food and Drug Administration reports that prescriptions for testosterone supplements have risen to 2.3 million from 1.3 million in just four years. There is such a condition as “low-T,” or hypogonadism, which can cause fatigue and diminished sex drive, and it becomes more common as men age. But according to a study published in JAMA Internal Medicine, half of the men taking prescription testosterone don’t have a deficiency. Many are just tired and want a lift. But they may not be doing themselves any favors. It turns out that the supplement isn’t entirely harmless: Neuroscientists are uncovering evidence suggesting that when men take testosterone, they make more impulsive — and often faulty — decisions. Researchers have shown for years that men tend to be more confident about their intelligence and judgments than women, believing that solutions they’ve generated are better than they actually are. This hubris could be tied to testosterone levels, and new research by Gideon Nave, a cognitive neuroscientist at the University of Pennsylvania, along with Amos Nadler at Western University in Ontario, reveals that high testosterone can make it harder to see the flaws in one’s reasoning. How might heightened testosterone lead to overconfidence? One possible explanation lies in the orbitofrontal cortex, a region just behind the eyes that’s essential for self-evaluation, decision making and impulse control. The neuroscientists Pranjal Mehta at the University of Oregon and Jennifer Beer at the University of Texas, Austin, have found that people with higher levels of testosterone have less activity in their orbitofrontal cortex. Studies show that when that part of the brain is less active, people tend to be overconfident in their reasoning abilities. It’s as though the orbitofrontal cortex is your internal editor, speaking up when there’s a potential problem with your work. Boost your testosterone and your editor goes reassuringly (but misleadingly) silent. © 2017 The New York Times Company

Keyword: Hormones & Behavior; Attention
Link ID: 23776 - Posted: 06.26.2017

By Karl Gruber Birds, fish, and even humans have shattered barriers when it comes to mating rituals, from which partner initiates the courting to which one picks up the check at a fancy restaurant. But things are a bit simpler for frogs, as males and females stick to clearly defined roles: Males serenade the females, and females pick their favorite males to mate. Now, a new study suggests that the smooth guardian frog of Borneo (Limnonectes palavanensis) is an exception to that rule. During the mating season, the female frogs sing to the males in an attempt to win them over—a reversal of the normal process. In fact, if you see a single frog surrounded by a bunch of serenading croakers, called a “lek,” it’s most likely a lucky male being courted by a chorus of females. Males occasionally belt out “advertisement calls” to let females know that they are available. After mating, it’s the males who stay behind to care for the eggs, even taking tadpoles to small ponds after they hatch. This is the first known example of role reversal in singing frogs, scientists write in a recent issue of Behavioral Ecology and Sociobiology. It may even represent the first case of full-blown sex role reversal, which would also require that males do the mate choosing. Researchers are working on that now, but they say that—judging by the high rate of female serenading—males may be the picky ones. © 2017 American Association for the Advancement of Science.

Keyword: Sexual Behavior
Link ID: 23755 - Posted: 06.21.2017

Laurel Hamers When things get hot, embryonic bearded dragon lizards turn female — and now scientists might know why. New analyses, reported online June 14 in Science Advances, reveal that temperature-induced changes in RNA’s protein-making instructions might set off this sex switch. The findings might also apply to other reptile species whose sex is influenced by temperature. Unlike most mammals, many species of reptiles and fish don’t have sex chromosomes. Instead, they develop into males at certain temperatures and females at others. Bearded dragon lizards are an unusual case because chromosome combinations and temperature are known to influence sex determination, says ecologist Clare Holleley of the Commonwealth Scientific and Industrial Research Organisation in Canberra, Australia (SN: 7/25/15, p.7). When eggs are incubated below 32° Celsius, embryonic bearded dragons with two Z chromosomes develop as male, while dragons with a Z and a W chromosome develop as female. But as temperatures creep above 32°, chromosomally male ZZ dragons will reverse course and develop as females instead. “They have two sex chromosomes, but they also have this temperature override,” Holleley says. By comparing bearded dragons that are female because of their chromosomes and those that are female because of environmental influences, Holleley and her colleagues hoped to sort out genetic differences that might point to how the lizards make the switch. The team collected RNA from the brain, reproductive organs and other tissues of normal female, normal male and sex-reversed female Australian central bearded dragons (Pogona vitticeps). Then, the researchers compared that RNA, looking for differences in the ways the lizards were turning on genes. |© Society for Science & the Public 2000 - 2017.

Keyword: Sexual Behavior
Link ID: 23745 - Posted: 06.15.2017

Hannah Devlin Science correspondent “Love looks not with the eyes, but with the mind. And therefore is winged Cupid painted blind,” Shakespeare wrote. Now scientists have pinpointed the specific patterns of brain activity that accompany romance, offering a new explanation for why love sends our judgement haywire. As a relationship takes root, the study found, the brain’s reward circuit goes into overdrive, rapidly increasing the value placed on spending time with one’s love interest. This, at least, was the case in the prairie vole, scientists’ animal model of choice for studying the neuroscience of love. Elizabeth Amadei, who co-led the work at Emory University in Atlanta, said: “As humans, we know the feelings we get when we view images of our romantic partners, but, until now, we haven’t known how the brain’s reward system works to lead to those feelings.” In order to get more direct access to what is happening in the brain, Amadei and colleagues turned to the North American voles, which as a species have almost perfected monogamy. They mate for life, share nest-building duties and have an equal role in raising their young – although, like humans, voles have the occasional “extramarital” fling. Using electrical probes, the scientists recorded directly from the brains of female voles as they encountered a potential partner, mated for the first time and began to show signs of having formed a lifelong bond, indicated by “huddling” behaviour.

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 23692 - Posted: 06.01.2017

By Ariana Eunjung Cha Depression is usually considered an issue parents have to watch out for starting in the turbulent teenage years. The CW channel, full of characters with existential angst about school, friends and young love, tells us so, as do the countless parenting books about the adolescent years in every guidance counselor's office. But what if by that time it's already too late? A large new study out this week contains some alarming data about the state of children's mental health in the United States, finding that depression in many children appears to start as early as age 11. By the time they hit age 17, the analysis found, 13.6 percent of boys and a staggering 36.1 percent of girls have been or are depressed. These numbers are significantly higher than previous estimates. Understanding the risk of depression is critically important because of the close link between depressive episodes and serious issues with school, relationships and suicide. While researchers have long known about the gender gap in depression, with more adult women than men suffering from the condition, the new numbers show that whatever divergent paths boys and girls take happens even earlier than expected. Published in the journal Translational Psychiatry, the study was based on data compiled from in-person interviews with more than 100,000 children who participated in the National Survey of Drug Use and Health from 2009 to 2014. The NSDUH is an annual survey on a representative sample of the U.S. population. Among the standard questions asked are ones about insomnia, irritability, and feelings of guilt or worthlessness that researchers used to “diagnose” survey participants with depression using diagnostic criteria from the Diagnostic and Statistical Manual of Mental Disorders. Through the survey, they were able to capture a broader group of children than those who have a formal diagnosis and who may be in treatment. © 1996-2017 The Washington Post

Keyword: Depression; Development of the Brain
Link ID: 23687 - Posted: 06.01.2017

By STEPH YIN A female and male get together. One thing leads to another, and they have sex. His sperm fuses with her egg, half of his DNA combining with half of her DNA to form an embryo. As humans, this is how we tend to think of reproduction. But there are many other bizarre ways reproduction can take place. For instance, scientists have discovered a fish carrying genes only from its father in the nucleus of its cells. Found in a type of fish called Squalius alburnoides, which normally inhabits rivers in Portugal or Spain, this is the first documented instance in vertebrates of a father producing a near clone of itself through sexual reproduction — a rare phenomenon called androgenesis — the researchers reported in the journal Royal Society Open Science on Wednesday. The possibility of androgenesis is just one of many mysteries about Squalius alburnoides. It’s not a species in the usual sense, but rather something called a hybrid complex, a group of organisms with multiple parental combinations that can mate with one another. The group is thought to have arisen from hybridization between females of one species, Squalius pyrenaicus, and males of another species, now extinct, that belonged to a group of fish called Anaecypris. To sustain its population, Squalius alburnoides mates with several other closely related species belonging to the Squalius lineage. That it can reproduce at all is unusual enough. Most hybrids, like mules, are sterile because the chromosomes from their parents of different species have trouble combining, swapping DNA and dividing — steps required for egg or sperm production. Squalius alburnoides males circumvent this problem by producing sperm cells that do not divide, and therefore contain more than one chromosome set. This is important because most animals, Squalius alburnoides included, need at least two chromosome sets to survive. © 2017 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 23669 - Posted: 05.27.2017

Tonight, our economics correspondent, Paul Solman, explores another potential connection: whether there’s a link between risk-taking in leadership, testosterone and the perceptions around gender. It’s part of his ongoing weekly series, Making Sense, which airs every Thursday. MAN: Welcome, everybody, to this CNBC discussion on the future of banking at the World Economic Forum. PAUL SOLMAN: Financial CEOs at Davos this year. ANDREW LIVERIS, CEO, Dow Chemical: Good morning. Mr. President. Andrew Liveris, Dow Chemical. PAUL SOLMAN: Manufacturing CEOs at the White House. MARK FIELDS, CEO, Ford Motor Company: CEO of Ford. DOUGLAS OBERHELMAN, CEO, Caterpillar: Chairman of Caterpillar. PRESIDENT DONALD TRUMP: Some of the great people in the world of business. PAUL SOLMAN: CEOs now being mentioned as the next president. But, in 2017, the vast majority of CEOs, 96 percent of the Fortune 500, are still men. JENNIFER LERNER, Harvard University: I think that this is socially constructed. The differences between males and females on a wide variety of things are smaller than the differences within males and within females. PAUL SOLMAN: Psychologist Jennifer Lerner studies gender and leadership at Harvard. We will hear more from her in a bit. But, first, let’s check in with economist Andy Kim, who has made a career out of studying CEOs in intriguingly quirky ways. Now, a few of you might remember Andy Kim teaching me two years ago the equestrian dance move in the hyper-viral video sensation “Gangnam Style,” part of his offbeat research showing that CEOs who become visible, for whatever reason, can see their stock price rise irrationally. Well, he presented his brand-new research, not yet published, at this year’s annual Economics Convention. His latest hypothesis is as offbeat as ever. ANDY KIM: There is a strong linkage between your facial masculinity and your risk-taking behavior. PAUL SOLMAN: Kim is now exploring a possible link between CEO risk-taking and the hormone testosterone, which, starting with mid-19th century experiments on roosters, has been linked to male dominance and aggression throughout the animal kingdom. But how do you measure testosterone in CEOs with little time and probably even less inclination to give Korean assistant finance professors blood or saliva samples? One possible way, thought Kim, would be to study their facial bone structure. © 1996 - 2017 NewsHour Productions LLC.

Keyword: Sexual Behavior; Aggression
Link ID: 23663 - Posted: 05.26.2017

James Gorman Darwin’s finches, those little birds in the Galápagos with beaks of different sizes and shapes, were instrumental in the development of the theory of evolution. Similar birds had large and small beaks and beaks in between, all related to what kinds of insects and seeds they ate. From one ancestor, it seemed, different adaptations to the environment had evolved, giving the birds that adapted a survival edge in a particular ecological niche — evolution by natural selection. Biologists who came later went on to identify the genetic changes that had produced different beak shapes. Now another group of finch-like birds has provided a similar example, but of a different kind of evolution, one driven not by the demands of the environment, but by the demands of female birds. Their preferences in color and pattern caused the evolution of different species of seedeater, all with the same behavior and diet, but with males that look different. That’s a process called sexual selection, which Darwin also wrote about. Leonardo Campagna, a researcher at Cornell University and the Cornell Lab of Ornithology, and a group of scientists from the United States and South America investigated nine species of southern capuchino seedeaters, doing full genomes for each one and reported their findings in Science Advances. They found that the DNA of all the species is remarkably similar, as are the birds. All the females look alike and all of the species feed on grass seeds plucked from grass stalks of living plants. Only the males are different. They have a wide variety of colorations and their courting songs are also distinct. Dr. Campagna and the other researchers found that differences between species DNA were all minimal, ranging from as little as 0.03 percent to as great as 0.3 percent. All the species showed variation in the same area, DNA that appeared to have a role in regulating genes for the pigment melanin. © 2017 The New York Times Company

Keyword: Evolution; Sexual Behavior
Link ID: 23660 - Posted: 05.25.2017

Elle Hunt About 150 years ago, and “almost a lifetime” either side, Charles Darwin was beleaguered by the problem of the peacock’s tail. Just the sight of a feather, he wrote in April 1860, “makes me sick!” The plumage of the male bird represented a hole in his theory of evolution. According to Victorian thinking, beauty was divine creation: God had designed the peacock for his own and humankind’s delight. In, On The Origin of Species, published the previous year, Darwin had challenged the dominant theory of creationism, arguing that man had been made not in God’s image but as a result of evolution, with new species formed over generations in response to their environment. But beauty, and a supposed aesthetic sense in animals (“We must suppose [that peahens] admire [the] peacock’s tail, as much as we do,” he wrote), took Darwin the best part of his life to justify – not least because the theory he eventually landed upon went against the grain of his entire worldview. Sexual selection was of strategic importance to Darwin, says Evelleen Richards, an honorary professor in history and philosophy of science at the University of Sydney: it was a naturalistic account for aesthetic differences between male and female animals of the same species, shoring up his defence of natural selection.

Keyword: Evolution; Sexual Behavior
Link ID: 23642 - Posted: 05.22.2017

Susan Milius The supermoms of the mammal world are big, shy redheads. Studying growth layers in orangutan teeth shows that mothers can nurse their youngsters for eight-plus years, a record for wild mammals. Teeth from a museum specimen of a young Bornean orangutan (Pongo pygmaeus) don’t show signs of weaning until 8.1 years of age. And a Sumatran orangutan (P. abelii) was still nursing during the few months before it was killed at 8.8 years, researchers report May 17 in Science Advances. Tests also show that youngsters periodically start to taper off their dependence on their mother’s milk and then, perhaps if solid food grows scarce, go back to what looks like an all-mom diet. Such on-again, off-again nursing cycles aren’t known in other wild mammals, says study coauthor Tanya Smith, an evolutionary anthropologist at Griffith University in Nathan, Australia. Marks of milk drinking Two images of a cross section of a first molar from a 4.5-year-old Bornean orangutan are shown. At left, numbers indicate days from birth (dotted line, starting with 0) when particular spots formed. At right, colors indicate concentrations of barium, which increase (shading toward red) when the youngster depended more on mother’s milk. A greenish swath at the top indicates nursing as an infant that gave way to blue as solid food became part of the diet. Yellow and red streaks indicate repeated times when the youngster again depended mostly on milk for nutrition. oragutan molar |© Society for Science & the Public 2000 - 2017.

Keyword: Sexual Behavior; Development of the Brain
Link ID: 23632 - Posted: 05.18.2017