Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases
Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.
Victoria E Brings & Mark J Zylka A study finds that pain hypersensitivity in male and female mice is differentially dependent on microglia and T cells, and describes a sex-specific response to microglia-targeted pain treatments. This sex difference will be important to consider when developing treatments for pain and other neurological disorders involving microglia and immune cells. Animal studies1, 2 have spawned great interest in using microglial inhibitors such as minocycline to treat pain in humans. However, these studies were conducted largely on male rodents. Now, Sorge et al.3 have evaluated several microglial inhibitors in nerve-injured mice of both sexes. The study—led by Jeffrey Mogil, who has championed the testing of males and females in pain studies4—found that microglial inhibitors did reduce allodynia, a form of pain hypersensitivity to touch, in males. Surprisingly, however, these inhibitors were ineffective in female mice, despite a robust activation of spinal microglia (Fig. 1). The authors instead found that cells of the adaptive immune system promote pain hypersensitivity in females. Although focused on pain, these findings could have implications for other neurological disorders that disproportionately affect one sex, such as autism and neurodegeneration, and in which microglia and immune cells are implicated5, 6. Figure 1: Pain mechanisms differ in male and female mice. Pain mechanisms differ in male and female mice. Nerve injury activates microglial cells in the spinal cord of male and female mice, but microglial inhibitors only block allodynia in males. P2RX4 is upregulated in males only. Female mice have about twice as many T cells as males. Testosterone increases PPARα and decreases PPARγ gene expression in T cells. Compounds that activate PPARα inhibit mechanical pain hypersensitivity (allodynia) in males, whereas those that activate PPARγ inhibit allodynia in females. © 2015 Macmillan Publishers Limited
Qazi Rahman In a recent Guardian article , Simon Copland argued that it is very unlikely people are born gay (or presumably any other sexual orientation). Scientific evidence says otherwise. It points strongly to a biological origin for our sexualities. Finding evidence for a biological basis should not scare us or undermine gay, lesbian and bisexual (LGB) rights (the studies I refer to do not include transgendered individuals, so I’ll confine my comments to lesbian, gay and bisexual people). I would argue that understanding our fundamental biological nature should make us more vigorous in promoting LGB rights. Let’s get some facts and perspective on the issue. Evidence from independent research groups who studied twins shows that genetic factors explain about 25-30% of the differences between people in sexual orientation (heterosexual, gay, lesbian, and bisexual). Twin studies are a first look into the genetics of a trait and tell us that there are such things as “genes for sexual orientation” (I hate the phrase “gay gene”). Three gene finding studies showed that gay brothers share genetic markers on the X chromosome; the most recent study also found shared markers on chromosome 8. This latest research overcomes the problems of three prior studies which did not find the same results. Gene finding efforts have issues, as Copland argues, but these are technical and not catastrophic errors in the science. For example, complex psychological traits have many causal genes (not simply “a gay gene”). But each of these genes has a small effect on the trait so do not reach traditional levels of statistical significance. In other words, lots of genes which do influence sexual orientation may fall under the radar. But scientific techniques will eventually catch up. In fact there are more pressing problems that I would like to see addressed, such as the inadequate research on female sexuality. Perhaps this is due to the stereotype that female sexuality is “too complex” or that lesbians are rarer than gay men. © 2015 Guardian News and Media Limited
By Sarah Schwartz Researchers have developed a chemical that transforms into a powerful hormone once inside a rat — but only in the brain, not the body. A protein in rats’ brains turns a chemical nicknamed DHED into the hormone estrogen, scientists report July 22 in Science Translational Medicine. This targeted treatment could provide estrogen to the brain and avoid potentially dangerous side effects in the body, the researchers say. “This is an interesting breakthrough,” says neuroendocrinologist Bruce McEwen of the Rockefeller University in New York City. The idea of treatments that affect the brain but not the body, or the body but not the brain, could be useful in treating a number of conditions, including cancer, he says. But the implications of this study for hormone replacement therapy in women is up for debate, a number of researchers say. In menopausal women or those who have had their ovaries surgically removed, lack of estrogen in the brain can cause symptoms such as hot flashes and sleep disturbances. Taking estrogen can relieve those symptoms but can cause side effects in the rest of the body, including an increased risk of certain cancers. The chemical DHED is nearly identical to natural human estrogen, but it has an extra oxygen atom. A specialized protein found in rodents’ brains recognizes the chemical and chops off the oxygen, turning DHED into estrogen. The body’s other organs lack this protein, so they can’t turn DHED into estrogen, says study author Laszlo Prokai, a chemical biologist at the University of North Texas Health Science Center in Fort Worth. © Society for Science & the Public 2000 - 2015.
THERE’S more to semen than sperm. In many animals, seminal fluid alters both the bodies and sometimes even the behaviour of females. Human semen, too, triggers changes in the uterus, and might have wider effects on women, aimed at just one goal. “It’s all about maximising the chances of the male reproducing,” says Sarah Robertson of the University of Adelaide in Australia. The effects are most striking in fruit flies: seminal fluid can make the females eat more, lay more eggs and be less receptive to other males. Now a team led by Tracey Chapman at the University of East Anglia in Norwich, UK, has found that male fruit flies selectively alter the chemical make-up of their seminal fluid. In the presence of rivals, the males produce more seminal proteins. “It came as a real surprise,” says Chapman. “It’s a sophisticated response to the social and sexual situation.” Some of their findings were presented at the Society for Molecular Biology and Evolution conference in Vienna, Austria, last week, including their discovery that one of these proteins is a “master regulator” of genes. Females exposed to it show a wide range of changes in gene expression. Chapman thinks this kind of seminal signalling is widespread in the animal world. The semen of people, pigs and mice affects the female reproductive tract, and the question is whether it can also produce behavioural responses in female mammals similar to those seen in fruit flies. © Copyright Reed Business Information Ltd.
By BENEDICT CAREY Women who develop slight but detectable deficits in memory and mental acuity late in life tend to decline faster than men with mild impairment, researchers reported on Tuesday. Some two-thirds of the five million Americans with Alzheimer’s disease are women, in part because women live longer. Researchers have searched in vain for decades to determine other reasons for the disparity. The authors of the new study, who presented their work at the Alzheimer’s Association International Conference in Washington, said their findings indicated nothing about possible causes of gender differences and had no immediate implications for treatment. “All we can say at this point is that there appears to be a faster trajectory for women than men” toward dementia, said Dr. P. Murali Doraiswamy, a professor of psychiatry at the Duke Institute for Brain Sciences and the study’s senior author. Katherine Amy Lin, a student of Dr. Doraiswamy’s and a co-author, presented the study. Previous research had found a steeper decline in women with mild deficits over a period of about a year. The new study extends that finding to up to eight years. “It’s a very interesting finding, but it’s also still early, so we’re limited in what conclusions we can draw,” said Dr. Edward D. Huey, a geriatric psychiatrist at Columbia University, who was not involved in the study. “I think of this as an excellent hypothesis generator. It’s something we need to investigate more deeply.” In the study, the Duke researchers analyzed scores on standard cognitive tests taken by 398 men and women, most in their 70s, being followed as part of a large, continuing Alzheimer’s trial. The participants have been taking the cognitive tests — as well as other tests, like PET scans — on average for four years, and as long as eight years. Controlling for factors that influence memory and mental acuity, like age, education and genetic predisposition, the research team found that women’s scores slipped by an average of about two points a year, compared with one point for men. The team also looked at a standard measure of life quality, rating how well people functioned socially: at home, at work and with family. That, too, slipped faster for women than for men, at about the same rate. © 2015 The New York Times Company
by Stephen Buchmann Flowers, bugs and bees: Stephen Buchmann wanted to study them all when he was a kid. "I never grew out of my bug-and-dinosaur phase," he tells NPR's Arun Rath. "You know, since about the third grade, I decided I wanted to chase insects, especially bees." These days, he's living that dream. As a pollination ecologist, he's now taking a particular interest in how flowers attract insects. In his new book, The Reason for Flowers, he looks at more than just the biology of flowers — he dives into the ways they've laid down roots in human history and culture, too. On the real 'reason for flowers' The reason for flowers is actually one word: sex. So, flowers are literally living scented billboards that are advertising for sexual favors, whether those are from bees, flies, beetles, butterflies or us, because quite frankly most of the flowers in the world have gotten us to do their bidding. But that's only the first stage because flowers, if they're lucky, turn into fruits, and those fruits and seeds feed the world. On the raucous secret lives of beetles One of my favorite memories is roaming the Napa foothills as a UC Davis grad student. And I would go to the wineries, of course, and in between I would find western spice bush, which is this marvelous flower that kind of smells like a blend between a cabernet and rotten fruit. And when you find those flowers and open them up, you discover literally dozens of beetles in there, mating, defecating, pollinating — having a grand time. © 2015 NPR
By THE EDITORIAL BOARD Scientific research has a gender gap, and not just among humans. In many disciplines, the animals used to study diseases and drugs are overwhelmingly male, which may significantly reduce the reliability of research and lead to drugs that won’t work in half the population. A new study published in the journal Nature Neuroscience suggests that research done on male animals may not hold up for women. Its authors reported that hypersensitivity to pain works differently in male and female mice. For males, immune cells called microglia appear to be required for pain hypersensitivity, and inhibiting their function also relieves the pain. But in female mice, different cells are involved, and targeting the microglia has no effect. If these differences occur in mice, they may occur in humans too. This means a pain drug targeting microglia might appear to work in male mice, but wouldn’t work on women. Failure to consider gender in research is very much the norm. According to one analysis of scientific studies that were published in 2009, male animals outnumbered females 5.5 to 1 in neuroscience, 5 to 1 in pharmacology, and 3.7 to 1 in physiology. Only 45 percent of animal studies involving depression or anxiety and only 38 percent involving strokes used females, even though these conditions are more common in women. In 1994, the National Institutes of Health confronted gender imbalance in clinical drug trials and began requiring that women and minorities be included in clinical studies; women now make up around half of clinical trial participants. In June, the N.I.H. announced that it would begin requiring researchers to take gender into account in preclinical research on animals as well. © 2015 The New York Times Company
Keyword: Sexual Behavior
Link ID: 21188 - Posted: 07.20.2015
Don’t do drugs, kids. Especially if you’re female. Women dependent on stimulants like cocaine and methamphetamine appear to have less grey matter, even after they stop using them. Weirdly, men’s brains don’t show this difference. The brain regions most affected are those involved in reward, emotion and learning – although it isn’t clear yet whether the smaller than average size of these brain areas could be a cause or effect of addiction. Jody Tanabe, at the University of Colorado Hospital in Aurora, hopes these results will help lead to a better understanding of sex differences in substance abuse, and better, more distinct treatments for women. Tanabe’s team used MRI scans to measure the brain volumes of 59 people previously dependent on stimulants and compared them with people who have never been dependent on these kinds of drugs. On average, the 28 women who had formerly been dependent on a stimulant drug had a smaller volume of grey matter in their prefrontal cortices, temporal lobes, insulae and other regions. This effect was not seen in men. Shrinking brains The women who had been addicted also differed in their personalities – on average, they were more impulsive and more reward-driven. We already know that women respond differently to stimulants: they start taking the drugs earlier, use larger quantities and may have more difficulty quitting. It’s possible that this pattern of female addiction could be linked to the brain size difference. However, it’s unclear whether less grey matter causes female addictive behaviours, or if addiction might shrink these brain regions. “The question of causality is complex. There is evidence for both pre-existing and post-drug changes in brain structure and function,” says Tanabe.
Simon Copland Over the past decade the idea that we are “born this way” — or that our sexuality is genetic — has become increasingly important. The mantra has become a political strategy, in particular for gay and lesbian communities, who see it as a way to protect themselves from discrimination. The movement has spawned blogs where people show pictures of their childhood to highlight the innate nature of their sexuality, and attacks on those who have questioned the theory. But do the politics match the science? People have been searching for biological explanations for sexual desires for centuries — primarily as a way to try and find a “cure” for “perverted desires”. In the most horrible of examples, the Nazi regime in Germany invested significant resources in attempts to find the reasons for homosexuality in attempt to cure it. In recent decades the search for a “gay gene” has intensified. In 1991, for example, Simon LeVay released a study that suggested small differences in the size of certain cells in the brain could influence sexual orientation in men. In 1993 this research turned to genetics, when Dean Hamer claimed that markers on the X chromosome could influence the development of same-sex orientation in men. The issue hit the headlines again last year after the release of a study from Dr. Alan Sanders. Sanders studied the genes on 409 pairs of gay brothers, finding they may share genetic markers on the X chromosome and chromosome 8. © 2015 Guardian News and Media Limited
By David Shultz Like many arthropods, spiders don’t have penises. Instead they rely on a set of modified appendages—termed pedipalps—to transfer sperm during reproduction. Previous studies had concluded that the pedipalps, which are basically modified arms emanating from the arachnid’s head, were lacking any sort of neurons that might convey a sense of touch. But new research, published online today in Biology Letters, suggests that the spider’s sex life isn’t an entirely numb deal. Using a combination of histological and computer-based techniques, scientists have identified neurons in the pedipalps of the Tasmanian cave spider (Hickmania troglodytes, seen above). Two main groups of nervous tissue were present: a nerve running to the tip of the sex organ, and two clusters of neurons in the palpal bulb—the region of the pedipalps used for transferring sperm. Though further research is needed to confirm the hypothesis, the team suspects that the sense of touch may enable the males to stimulate the females and even provide feedback about the quality of their mate. The latter hypothesis is especially intriguing because the analyses also revealed that one of the glands in the spider’s sex organ was directly innervated. The team believes this might mean the spiders can control the quality and volume of their ejaculate—reserving the best secretions for the choicest mates. © 2015 American Association for the Advancement of Science
Keyword: Sexual Behavior
Link ID: 21145 - Posted: 07.08.2015
By Sabrina Imbler To our knowledge, there’s no correlation between a man’s singing ability and his care and attentiveness as a father. But any Pavarotti among the nightingales will serenade his mate while she sits on her eggs. And after they hatch he will visit the nest about 16 times each hour to feed their offspring. Because, among nightingales at least, the best singers also make the best fathers. So finds a study in the journal BMC Evolutionary Biology. [Conny Bartsch, Michael Weiss and Silke Kipper, Multiple song features are related to paternal effort in common nightingales] Some 80 percent of birds practice biparental care, meaning both the male and female rear their offspring together. So it’s crucial for a female bird to pick as a mate the most promising father—both genetically and behaviorally. Female birds look for signs of fitness that range from the flamboyant plumage of the peacock to the bizarre dances of birds of paradise. And for nightingales, it’s the most elaborate song that apparently wins the day. The average male has some 180 tunes in his repertoire. These avian Sinatras vocalize highly variable song types including buzzes, whistles and trills. And such virtuoso singing seems to signal the female that this is a guy she can count on. That is, when it’s time to help raise the kids, he’s not a flight risk. © 2015 Scientific American
Taunya English What do we know about the power of food to rev up sex drive? Not much. "Really, science has not figured out what determines sexual motivation and sexual attraction. If we knew the answer to that, we'd probably be richer than Pfizer after they invented Viagra," says Dolores Lamb, director of the Center for Reproductive Medicine at Baylor College of Medicine. She hasn't seen any compelling evidence that any particular food can intensify desire. Lamb is a men's health researcher and knows a lot about the intricacies of male plumbing, but she says desire is largely psychological. Even medicines that treat erectile dysfunction can't create enthusiasm. "So the trigger still has to be up in the brain," Lamb says. Still, the idea persists that ginger stirs up lust, or that hot peppers make you hot. "Probably for some folks they do, and it's certainly fun to try," Lamb says. Some legendary aphrodisiacs do have a chemical here or a nutrient there that might support sexual health, but not enough of it to make an immediate difference in the bedroom. Red, juicy watermelon, for example, contains the amino acid citrulline, and that plant nutrient is healthy for erectile tissue in both men and women. But most of the amino acid is found in the rind of the fruit. Consider chili peppers. Capsaicin, which is what provides the heat in a jalapeno, also raises your metabolism and releases feel-good endorphins. "You get kind of a chill down the back of your neck and kind of a tingly, good sensation," Lamb says. "Gets blood flowing better." © 2015 NPR
Keyword: Sexual Behavior
Link ID: 21134 - Posted: 07.06.2015
by Michael Le Page It's good to be mixed-up. People whose parents are distantly related are, on average, taller, smarter and better educated than those whose parents are close relatives. Based on what we know about plants and animals, biologists have long suspected that people of mixed parentage have a genetic advantage. Now an extensive study may have confirmed the hunch. "It does imply that people who come from very different ancestry would be a bit taller and a bit more cognitively able," says team member Jim Wilson of the University of Edinburgh, UK. It has long been known that children are more likely to suffer from genetic diseases if their parents are close relatives, because they may inherit the same harmful gene variants from their mother and father. To probe the wider implications, Wilson and his colleagues analysed genome and life history data from 110 genome studies involving 350,000 people from Africa, Asia, Europe and North America. They were surprised to find no evidence of a link between having closely related parents and most of the traits they looked at, such as cholesterol levels, blood pressure and rates of diabetes. © Copyright Reed Business Information Ltd
by Lisa Grossman Marriage for all, no gay gene required. For same-sex couples in the US, 26 June was a landmark date: the Supreme Court legalised marriage between two men or two women in all 50 states. "[Same-sex couples] ask for equal dignity in the eyes of the law," wrote Associate Justice Anthony Kennedy in the decision. "The Constitution grants them that right." But one thing the decision didn't do was declare sexual orientation a "suspect class" under the law, which would have given it the same protection as race. One of the criteria for this classification is that the trait must be immutable – an argument that the gay rights movement has internalised under the banner of "we're born this way". But although there is some evidence that sexual orientation has a genetic component, most scientists agree that it's not that simple. "There's significant consensus in the scientific community that there's enough different interacting causes for sexual orientation that two different individuals can be gay for different combinations of reasons," says sexuality researcher Lisa Diamond at the University of Utah. "I think all the evidence suggests that we're born with an underlying capacity and then that capacity interacts with a whole bunch of other influences," she says – whether they be prenatal, genetic or environmental. © Copyright Reed Business Information Ltd
Keyword: Sexual Behavior
Link ID: 21117 - Posted: 07.01.2015
by Colin Barras Men often lose their sex drive with age – and so, it seems do male Drosophila. Tsai-Feng Fu at the National Chi Nan University in Taiwan and his colleagues suspected that low levels of dopamine in the flies were to blame. Almost 300 neurones in the fruit-fly brain use dopamine. Comparing those linked to sexual function in elderly 40-day-old male flies and sprightly 10-day-old flies, Fu found the older neurones carried 10 times less dopamine. Boosting levels lengthened the time the older flies spent trying to mate. There are obviously big differences between a man's brain and that of a male Drosophila, but Fu says that the new results could provide a useful starting point for in-depth studies that may have clinical implications. For instance, that research might eventually identify ways to fine-tune dopamine levels in humans, perhaps to reverse age-related declines in sexual drive, or even to suppress an overactive libido. We already have therapies for treating male sexual dysfunction – notably the drug viagra. But probing the link between dopamine and sexual dysfunction is still important. For instance, dopamine-replacement therapy is one of the most effective treatments for Parkinson's disease – but the therapy can lead to harmful compulsive sexual behaviour. But Wendi Neckameyer at the Saint Louis University School of Medicine in Missouri isn't sure we should talk about potential implications for men just yet – it's enough to say that the researchers "have begun to tease out an incredibly complex neural circuit", she says. © Copyright Reed Business Information Ltd
Keyword: Sexual Behavior
Link ID: 21115 - Posted: 07.01.2015
Moheb Costandi Different immune cells regulate pain sensitization in male and female mice, according to research published on 29 June in Nature Neuroscience1. The surprising biological divide may explain why some clinical trials of pain drugs have failed, and highlights shortcomings in the way that many researchers design their experiments. The immune system has important roles in chronic pain, with cells called microglia being key players. Microglia express a protein called brain-derived neurotrophic factor (BDNF) to signal to spinal-cord neurons. When injury or inflammation occurs, this signal sensitizes the body to pain, so that even light touch hurts. Robert Sorge, a psychologist at the University of Alabama in Birmingham, and his colleagues induced persistent pain and inflammation in healthy male and female mice by severing two of the three sciatic nerve branches in their hind paws. Seven days later, they injected the animals with one of three drugs that inhibit microglial function. They found that all three drugs reversed pain sensitization in the male animals, as had been previously reported. But the treatments had no effect on the females, even though the animals had displayed equivalent levels of pain. The researchers also genetically engineered mice in which the BDNF gene could be deleted in microglia at any time during the animals' lives. At first, these animals exhibited normal responses to a nerve injury. Killing the microglia one week later extinguished that hypersensitivity in the male animals, but not in the females. This confirmed that in males, hypersensitivity to pain depends on BDNF signals from microglia, but that in females it is mediated by some other mechanism. © 2015 Nature Publishing Group,
By Christopher Intagliata Two decades ago, Swiss researchers had women smell the tee shirts that various men had slept in for two nights. Turned out that if women liked the aroma of a particular shirt, the guy who’d worn it was likely to have genetically coded immunity that was unlike the woman’s. Well the effect isn't just limited to sweaty shirts. Turns out we all smell things a little differently—you pick up a note of cloves, say, where I smell something more soapy—and that too gives clues to our degree of genetic similarity. Researchers tried that test with 89 people—having them sniff a couple dozen samples, and label each one using terms like lemony, coconut, fishy and floral. And each volunteer classified the scents differently enough that the researchers could single them out in subsequent tests, based on what they called each subject’s "olfactory fingerprint." Researchers then repeated that sniff test on another 130 subjects. But this time they did a blood test, too, to figure out each person's HLA type—an immune factor that determines whether you'll reject someone's organ, for example. They found that people who perceived smells similarly also had similar HLA types. Study author Lavi Secundo, a neuroscientist at the Weizmann Institute of Science in Israel, says the smell test could have real-world applications. "For organ donation you can think of this method as a quick, maybe a quick and dirty, method to sift between the best and the rest." He and his colleagues say it might even eliminate the need for 30 percent of the HLA tests done today. The work appears in the Proceedings of the National Academy of Sciences. [Lavi Secundo et al, Individual olfactory perception reveals meaningful nonolfactory genetic information] © 2015 Scientific American
Helen Shen In April 2011, Robert Froemke and his team were reprogramming the brains of virgin mice with a single hormone injection. Before the treatment, the female mice were largely indifferent to the cries of a distressed baby, and were even known to trample over them. But after an injection of oxytocin, the mice started to respond more like mothers, picking up the mewling pup in their mouths. Froemke, a neuroscientist at New York University's Langone Medical Center in New York City, was monitoring the animals' brains to find out why that happened. At first, the mice showed an irregular smattering of neural impulses when they heard the baby's cries. Then, as the oxytocin kicked in, the signal evolved into a more orderly pattern typical of a maternal brain. The study showed in unusual detail how the hormone changed the behaviour of neurons1. “Oxytocin is helping to transform the brain, to make it respond to those pup calls,” Froemke says. Oxytocin has been of keen interest to neuroscientists since the 1970s, when studies started to show that it could drive maternal behaviour and social attachment in various species. Its involvement in a range of social behaviours2, including monogamy in voles, mother–infant bonding in sheep, and even trust between humans, has earned it a reputation as the 'hug hormone'. “People just concluded it was a bonding molecule, a cuddling hormone, and that's the pervasive view in the popular press,” says Larry Young, a neuroscientist at Emory University in Atlanta, Georgia, who has been studying the molecule since the 1990s. “What we need to start thinking about is the more fundamental role that oxytocin has in the brain.” © 2015 Nature Publishing Group,
by Curtis Abraham A step forward for equal LGBT rights in Africa. Last week, the influential Academy of Science of South Africa (ASSAf) published a study on the science of human sexual diversity. A comprehensive review of recent scientific papers on the subject, it concluded that sexual behaviour is naturally varied, and discrimination unjustified. It stated that there is no evidence that orientation can be altered by therapy or that being gay is contagious. The report also sets straight the idea that homosexuality is a Western malaise: "There is no basis for the view that homosexuality is 'un-African' either in the sense of it being a 'colonial import', or on the basis that prevalence of people with same-sex or bisexual orientations is any different in African countries compared to countries on any other continent." Going further, the report asserted not only that tolerance of sexual diversity benefits communities but it positively affects public health, civil society and long-term economic growth. Zero tolerance Launched at the Seventh South African AIDS Conference in Durban, the study comes a year after the Ugandan government passed a law imposing a life sentence on anyone who has sexual relations with someone of the same sex. Other countries, including Burundi, Cameroon and Nigeria, then passed similar anti-gay laws. © Copyright Reed Business Information Ltd.
Keyword: Sexual Behavior
Link ID: 21071 - Posted: 06.18.2015
Tom Bawden The mystery behind the nightingale’s beautiful song has been revealed, with scientists finding that male birds sing complex notes to prove to females that they would be a good father to their children. Nightingales use their songs to advertise their family values, according to new research which discovers that the better the singer, the more support they are likely to offer their young family by feeding and defending them from predators. But while the beauty comes from the complexity of the song, the effect it has on the females is based on something far more mundane – the amount of effort the singer has put into his performance. Researchers at the Freie Universitat Berlin found that complicated choral arrangements are much harder to sing, especially when they include frequent appearances of long buzzing sounds and require the bird to be in good physical condition. “We don’t think the female is concerned with the beauty of the song but rather the information encoded in the song that tells her about the singer’s characteristics – his age, where he was raised, the strength of his immune system and how motivated he is to contribute to bringing up the young,” Professor Silke Kipper, one of the report’s authors, told The Independent. “The songs can also be a good indication of the bird’s ability to learn, which is another important characteristic of a good parent.” © independent.co.uk