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

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By Sofie Bates Make some noise for the white bellbirds of the Brazilian Amazon, now the bird species with the loudest known mating call. The birds (Procnias albus) reach about 125 decibels on average at the loudest point in one of their songs, researchers report October 21 in Current Biology. Calls of the previous record-holder — another Amazonian bird called the screaming piha (Lipaugus vociferans) — maxed out around 116 decibels on average. This difference means that bellbirds can generate a soundwave with triple the pressure of that made by pihas, says Jeff Podos, a behavioral ecologist at the University of Massachusetts Amherst, who did the research along with ornithologist Mario Cohn-Haft, of the National Institute of Amazon Research in Manaus, Brazil. The team measured sound intensity from three pihas and eight bellbirds. Each sounded off at different distances from the scientists. So to make an accurate comparison, the researchers used rangefinder binoculars, with lasers to measure distance, to determine how far away each bird was. Then, they calculated how loud the sound would be a meter from each bird to crown a winner. The small white bellbird, which weighs less than 250 grams, appears to be built for creating loud sounds, with thick abdominal muscles and a beak that opens extra wide. “Having this really wide beak helps their anatomy be like a musical instrument,” Podos says. Being the loudest may come with a cost: White bellbirds can’t hold a note for long because they run out of air in their lungs. Their loudest call sounds like two staccato beats of an air horn while the calls of screaming pihas gradually build to the highest point. © Society for Science & the Public 2000–2019

Keyword: Sexual Behavior; Hearing
Link ID: 26733 - Posted: 10.22.2019

Zoë Corbyn At a time when women’s reproductive freedoms are under attack, any suggestion that the birth control pill could be problematic feels explosive. But Sarah E Hill, a professor of social psychology at the Texas Christian University in Fort Worth, Texas argues we need to talk about how oral contraceptives are affecting women’s thinking, emotions and behaviour. How the Pill Changes Everything: Your Brain on Birth Control is her new book about the science behind a delicate subject. Some US states have recently made it harder to get an abortion and the Trump administration is doing its best to chisel away at access to birth control. Is your book trying to dissuade women from using the pill? My institution was founded as a Christian school, but it doesn’t have a particular religious bent now. My goal with this book is not to take the pill away or alarm women. It is to give them information they haven’t had up until now so they can make informed decisions. The pill, along with safe, legalised abortions, are the two biggest keys to women’s rights. But we also have a blind spot when it comes to thinking about how changing women’s sex hormones – which is what the pill does – influences their brains. For a long time, women have been experiencing “psychological” side-effects on the pill but nobody was telling them why. The backlash we are seeing against the pill, particularly with millennial women walking away from it, I think is because women haven’t felt right on it and have grown weary of doctors patting them on their heads and telling them they are wrong. The more information women have, the more it will bring them back to the pill. © 2019 Guardian News & Media Limited

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 26723 - Posted: 10.19.2019

Hannah Devlin Science correspondent Boosting testosterone levels significantly improves female athletic performance, according to one of the first randomised controlled trials. The findings come as the International Association of Athletics Federations (IAAF) announced on Monday it would impose an upper limit for testosterone levels on trans female athletes competing in middle-distance events. Testosterone was assumed to be performance-enhancing and a factor in explaining differences in strength and endurance between men and women. However, there was a surprising lack of evidence on the impact of testosterone in women and the question had become mired in controversy following a series of rulings in professional sport. The latest research confirmed that testosterone significantly increases endurance and lean muscle mass among young women, even when given for a relatively short period. Angelica Hirschberg, a gynaecologist for the Swedish Olympic Committee based at Karolinska University Hospital and the study’s first author, said the results were the first to show a causal effect of testosterone on physical performance in women. “This has not been demonstrated previously because most studies have been performed in men,” she said. “Furthermore, the study shows the magnitude of performance enhancement by testosterone. Testosterone levels increased more than four times but were still much below the male range. The improvement in endurance performance by the increased testosterone levels was more than 8% – this is a huge effect in sports.” © 2019 Guardian News & Media Limited

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 26706 - Posted: 10.16.2019

Nicola Davis A possible explanation for one of biology’s greatest mysteries, the female orgasm, has been bolstered by research showing that rabbits given antidepressants release fewer eggs during sex. The human female orgasm has long proved curious, having no obvious purpose besides being pleasurable. The scientists behind the study have previously proposed it might have its evolutionary roots in a reflex linked to the release of eggs during sex – a mechanism that exists today in several animal species, including rabbits. Since humans have spontaneous ovulation, the theory goes that female orgasm may be an evolutionary hangover. They say the new experiment supports the idea. “We know there is a reflex [in rabbits], but the question [is] could this be the same one that has lost the function in humans?” said Dr Mihaela Pavličev a researcher at the University of Cincinnati who co-authored the study. To explore the question the team gave 12 female rabbits a two-week course of fluoxetine (trade name Prozac) – an antidepressant known to reduce the capacity for women to orgasm – and looked at the number of eggs released after the animals had sex with a male rabbit called Frank. The results, published in the Proceedings of the National Academy of Sciences, showed that rabbits given the antidepressants released 30% fewer eggs than nine rabbits that were not given Prozac but still mated with Frank. © 2019 Guardian News & Media Limited

Keyword: Sexual Behavior; Evolution
Link ID: 26659 - Posted: 10.01.2019

Alison Flood Caroline Criado Perez’s exposé of the gender data gap that has created a world biased against women has won her the Royal Society science book prize. Criado Perez’s Invisible Women, which explores how everything from speech-recognition software to bulletproof vests, from medical tests to office temperature controls are designed for men as a default, was called a brilliant exposé by chair of judges and Oxford professor Nigel Shadbolt. He said the book had made him, as an AI researcher and data scientist, look at his field afresh. “[Criado Perez] writes with energy and style, every page full of facts and data that support her fundamental contention that in a world built for and by men gender data gaps, biases and blind spots are everywhere,” he said. The author and feminist campaigner who successfully pushed for Jane Austen to be featured on the UK’s £10 note, called her £25,000 win on Monday night a huge relief. “Obviously it’s a huge honour, but mainly because it has the official endorsement of scientists and so it can’t be dismissed now, and that’s so important,” she said. “Writing this book was hellish. It really tested my mental strength to its limits, partly because it was a really emotional book to write because of the impact this is having on women’s lives and how angry and upsetting it was to keep coming across this gap in the data. But also it was very challenging because it was a book about the whole world and everything in it, and I had to work out how to synthesise that into something manageable.” © 2019 Guardian News & Media Limited

Keyword: Sexual Behavior
Link ID: 26646 - Posted: 09.25.2019

Daniel Pfau I came out to a Christian counselor during a therapy session in 2001 when I was 14. He convinced me to engage in conversion therapy, a pseudoscientific practice to change an individual’s sexual orientation based in the assumption that such behaviors are “unnatural.” He produced an article describing a talk at that year’s American Psychological Association conference that indicated the therapy worked. This painful experience encouraged me, when I started my scientific career, to examine queerness in biology. The queer community, 25 million years (or more) in the making Understanding how complex human relationships developed requires a complete picture of our social behavior during evolution. I believe leaving out important behaviors, like same-sex sexual behavior, can bias the models we use to explain social evolution. Many researchers have postulated how queer behaviors, like same-sex sexual behavior, may have developed or how they are expressed. Recently, scientists at the Broad Institute of Harvard and MIT published a paper suggesting a genetic component to same-sex sexual behavior expression in modern humans. However, no studies provide an argument of when queer behavior may have arisen during humans’ evolution. Such research would push back against the assertions I encountered during my youth, that queerness is a modern aberration. © 2010–2019, The Conversation US, Inc.

Keyword: Sexual Behavior; Evolution
Link ID: 26632 - Posted: 09.21.2019

By Kim Tingley Men have a far greater appetite for sex and are more attracted to pornography than women are. This is the timeworn stereotype that science has long reinforced. Alfred Kinsey, America’s first prominent sexologist, published in the late 1940s and early 1950s his survey results confirming that men are aroused more easily and often by sexual imagery than women. It made sense, evolutionary psychologists theorized, that women’s erotic pleasure might be tempered by the potential burdens of pregnancy, birth and child rearing — that they would require a deeper emotional connection with a partner to feel turned on than men, whose primal urge is simply procreation. Modern statistics showing that men are still the dominant consumers of online porn seem to support this thinking, as does the fact that men are more prone to hypersexuality, whereas a lack of desire and anorgasmia are more prevalent in women. So it was somewhat surprising when a paper in the prestigious journal P.N.A.S. reported in July that what happens in the brains of female study subjects when they look at sexual imagery is pretty much the same as what happens in the brains of their male counterparts. The researchers, led by Hamid Noori at the Max Planck Institute for Biological Cybernetics in Germany, weren’t initially interested in exploring sexual behavior. They were trying to find ways to standardize experiments that use functional magnetic resonance imaging (fM.R.I.) to observe how the brain responds to visual stimuli. In order to do that, they needed to compare past studies that used similar methods but returned diverse results. They happened to choose studies in which male and female volunteers looked at sexual imagery, both because doing so tends to generate strong signals in the brain, which would make findings easier to analyze, and because this sort of research has long produced “inconsistent and even contradictory” results, as they note in their paper. Identifying the reasons for such discrepancies might help researchers design better experiments. © 2019 The New York Times Company

Keyword: Sexual Behavior; Brain imaging
Link ID: 26622 - Posted: 09.18.2019

By Emily Oster At some point or another, most books about the brain come back to the story of Phineas Gage. Gage was a railroad worker in the 19th century. In an unfortunate 1848 accident, a large steel spike was driven through his eye and out the other side of his head, taking some of his brain with him (this is the point in the story where my 8-year-old told me to please stop telling it). Amazingly, Gage survived the accident with much of his faculties intact. What did change was his personality, which, by many reports, became more aggressive and belligerent. Gage’s doctor wrote up his case, arguing that it suggested “civilized conduct” was localized in a particular part of the brain — specifically, the part he had lost. Science was off in search of where in the brain various skills were kept, with the idea that the brain was a kind of map, with little areas for, say, walking or talking or hearing or smelling. This proceeded, albeit slowly; for a while, there wasn’t much of a way to study this other than by looking at people with traumatic brain injuries. So it’s understandable that the development of technologies to study intact brains caused a lot of excitement. Generating the most discussion in recent years has been functional magnetic resonance imaging (or fMRI), which allows researchers to measure oxygen flow to the brain and identify which parts activate in response to varying stimuli. These technologies have not always lived up to the hype. The mechanics and statistics of processing fMRI imaging data have turned out to be far more complex than initially imagined. As a result there were many false claims made about which parts of the brain “controlled” different aspects of behavior or actions. The best, or at least funniest, example of this was a paper that showed how cutting-edge statistical analysis of fMRI made it possible to identify parts of the brain that responded differently to happy or sad faces. Sounds good, until you learn that the subject for this experiment was a dead fish. © 2019 The New York Times Company

Keyword: Sexual Behavior; Brain imaging
Link ID: 26594 - Posted: 09.10.2019

/ By Hope Reese In her new book “Gender and Our Brains,” cognitive neuroimaging professor Gina Rippon explains that brains aren’t gendered, but research can be. The differences among women as a group, or men as a group, are greater than the differences between men and women, Rippon says. Rippon sifts through centuries of research into supposed differences in areas such as behavior, skills, and personality, and shows that external factors like gender stereotypes and real-world experiences are the likely cause of any detectable differences in mental processing. And she demonstrates that the differences among women as a group, or among men as a group, are much greater than the differences between men and women. She cites a 2015 study looking at 1,400 brain scans as an example. Comparing 160 brain structures in the scans — identifying areas that were, on average, larger in men or in women — researchers could not find any scans that had all “male” traits, or all “female” traits — physical attributes such as weight or tissue thickness. “The images were, literally, of a mosaic,” she says. “We’re trying to force a difference into data that doesn’t exist.” Rippon teaches cognitive neuroimaging — the study of behavior through brain images — at Aston University in England. For this installment of the Undark Five, I spoke with her about how neuroimages are misinterpreted and whether PMS is real, among other topics. Here is our conversation, edited for length and clarity. Undark: Scientists have been trying to find differences in the brains of men and women for years. What are some examples of how the cherry-picking approach is problematic? Gina Rippon: It’s what I call the “hunt the differences” agenda, which started about 200 years ago when scientists were starting to understand the importance of the brain in explaining human behavior and human ability. Copyright 2019 Undark

Keyword: Sexual Behavior; Brain imaging
Link ID: 26584 - Posted: 09.07.2019

By Emily Underwood Of the many proposed triggers for autism, one of the most controversial is the “extreme male brain” hypothesis. The idea posits that exposure to excess testosterone in the womb wires both men and women to have a hypermasculine view of the world, prioritizing stereotypically male behaviors like building machines over stereotypically female behaviors like empathizing with a friend. Now, a study is raising new doubts about this theory, finding no effect of testosterone on empathy in adult men. The work does not directly address whether high levels of prenatal testosterone cause autism or lack of empathy. That would require directly sampling the hormone in utero, which can endanger a developing fetus. But the new study’s large size—more than 600 men—makes it more convincing than similar research in the past, which included no more than a few dozen participants, experts say. The extreme male brain hypothesis was first proposed by psychologist Simon Baron-Cohen at the University of Cambridge in the United Kingdom. In 2001, he and colleagues found that women given a single hefty dose of testosterone fared significantly worse at the Reading the Mind in the Eyes test (RMET), which asked them to gauge the emotional states of others based on their facial expressions. The women’s performance seemed to track with a controversial metric called the 2D:4D ratio, the relative lengths of the second and fourth fingers. Men—and people with autism—tend to have a longer ring finger than index finger, and some researchers believe that is due to higher prenatal exposure to testosterone. (Others are skeptical.) © 2019 American Association for the Advancement of Science

Keyword: Autism; Sexual Behavior
Link ID: 26571 - Posted: 09.04.2019

By Pam Belluck How do genes influence our sexuality? The question has long been fraught with controversy. An ambitious new study — the largest ever to analyze the genetics of same-sex sexual behavior — found that genetics does play a role, responsible for perhaps a third of the influence on whether someone has same-sex sex. The influence comes not from one gene but many, each with a tiny effect — and the rest of the explanation includes social or environmental factors — making it impossible to use genes to predict someone’s sexuality. “I hope that the science can be used to educate people a little bit more about how natural and normal same-sex behavior is,” said Benjamin Neale, a geneticist at the Broad Institute of M.I.T. and Harvard and one of the lead researchers on the international team. “It’s written into our genes and it’s part of our environment. This is part of our species and it’s part of who we are.” The study of nearly half a million people, funded by the National Institutes of Health and other agencies, found differences in the genetic details of same-sex behavior in men and women. The research also suggests the genetics of same-sex sexual behavior shares some correlation with genes involved in some mental health issues and personality traits — although the authors said that overlap could simply reflect the stress of enduring societal prejudice. Even before its publication Thursday in the journal Science, the study has generated debate and concern, including within the renowned Broad Institute itself. Several scientists who are part of the L.G.B.T.Q. community there said they were worried the findings could give ammunition to people who seek to use science to bolster biases and discrimination against gay people. One concern is that evidence that genes influence same-sex behavior could cause anti-gay activists to call for gene editing or embryo selection, even if that would be technically impossible. Another fear is that evidence that genes play only a partial role could embolden people who insist being gay is a choice and who advocate tactics like conversion therapy. © 2019 The New York Times Company

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 26555 - Posted: 08.30.2019

By Lindsey Bever There is no one gene that determines a person’s sexual orientation, but genetics — along with environment — play a part in shaping sexuality, a massive new study shows. Researchers analyzed DNA from hundreds of thousands of people and found that there are a handful of genes clearly connected with same-sex sexual behavior. The researchers say that, although variations in these genes cannot predict whether a person is gay, these variants may partly influence sexual behavior. Andrea Ganna, lead author and European Molecular Biology Laboratory group leader at the Institute of Molecular Medicine in Finland, said the research reinforces the understanding that same-sex sexual behavior is simply “a natural part of our diversity as a species.” The new study, published Thursday in the journal Science, is not the first to explore the link between genetics and same-sex behavior, but it is the largest of its kind, and experts say it provides one of the clearest pictures of genes and sexuality. Ganna, who is also an instructor at Massachusetts General and Harvard, and an international team of scientists examined data from more than 470,000 people in the United States and the United Kingdom to see whether certain genetic markers in their DNA were linked to their sexual behavior. Specifically, the researchers used data from the UK Biobank study and from the private genomics company 23andMe, which included their DNA data and responses to questions about sexual behaviors, sexual attraction and sexual identity. More than 26,000 participants reported at least one sexual encounter with someone of the same sex. Earlier studies, the researchers said, weren’t large enough to reveal the subtle effects of individual genes. © 1996-2019 The Washington Post

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 26554 - Posted: 08.30.2019

By Annie Roth Kalutas live fast and die young — or, at least, the males do. Male kalutas, small mouselike marsupials found in the arid regions of Northwestern Australia, are semelparous, meaning that shortly after they mate, they drop dead. This extreme reproductive strategy is rare in the animal kingdom. Only a few dozen species are known to reproduce in this fashion, and most of them are invertebrates. Kalutas are dasyurids, the only group of mammals known to contain semelparous species. Only around a fifth of the species in this group of carnivorous marsupials — which includes Tasmanian devils, quolls and pouched mice — are semelparous and, until recently, scientists were not sure if kalutas were among them. Now there is no doubt that, for male kalutas, sex is suicide. In a study, published in April in the Journal of Zoology, researchers from the University of Western Australia and the University of Queensland confirmed that kalutas exhibit what is known as obligate male semelparity. “We found that males only mate during one highly synchronized breeding season and then they all die,” said Genevieve Hayes, a vertebrate ecologist and the lead author of the study. Dr. Hayes and her colleagues monitored the breeding habits of a population of kalutas in Millstream Chichester National Park in Western Australia during the 2013 and 2014 breeding seasons. In both seasons, the researchers observed a complete die-off of males. Although male kalutas have exhibited semelparity in captivity, this was the first time it had been seen in the wild. Kalutas evolved independently of other semelparous dasyurids, so the confirmation that male kalutas die after mating suggests that this unorthodox reproductive strategy has evolved not once, but twice in dasyurids.

Keyword: Sexual Behavior
Link ID: 26552 - Posted: 08.29.2019

Patti Neighmond The pathway to opioid abuse for women often starts with a prescription from the doctor's office. One reason is that women are more likely than men to seek help for pain. Pain researchers say that not only do women suffer more painful conditions, they actually perceive pain more intensely than men do. "The burden of pain is substantially greater for women than men," says researcher and psychologist Roger Fillingim, "and that led pain researchers like myself to wonder if the pain perception system is different in women than in men." For more than two decades, Fillingim has been studying gender differences and pain, most recently at the University of Florida's Pain Research and Intervention Center of Excellence, where he is director. He recruits healthy male and female volunteers to take part in experimental pain sessions using various painful stimuli, including pressure, heat, cold and electrical stimulation. Probes are typically applied to the hand or arm. As intensity of the stimuli is increased, volunteers are asked to rate their pain on a scale of zero to 10, where zero is no pain and 10 is the most intense pain one can imagine. If volunteers report pain levels at 10, Fillingim stops the experiment immediately. "On average, women report the same stimuli to be more painful than men," Fillingim says, emphasizing that the same stimulus is applied to everybody, so if there are differences in how painful the experience is, it can't be because of the stimulus because it's calibrated to be the same for all. © 2019 npr

Keyword: Pain & Touch; Sexual Behavior
Link ID: 26546 - Posted: 08.27.2019

Ammar Kalia Three years ago, Paul (not his real name), now 31, went to the doctor with stomach pains. His blood test came back with low testosterone levels. “We went to see a urologist and he said bluntly that we wouldn’t have any options to have kids with my sperm – we would have to use a donor or adopt,” he says. “My wife immediately burst into tears.” The couple had been trying for a child since they married in 2015. Paul was also devastated. “It put so much stress on me, because I thought I couldn’t give my wife or my family what they so desperately wanted.” Eventually, Paul was diagnosed with Klinefelter syndrome. Affecting about one in 600 men, it is one of the most common genetic conditions in the UK, yet most people have never heard of it – including many who have it. Its symptoms – extra height, persistent tiredness, reduced bodily hair and small testes – can be difficult to identify, meaning it often goes unnoticed by patients and GPs. Untreated, however, it can lead to reduced testosterone and infertility, and even increased prevalence of testicular cancer. The non-hereditary syndrome was first discovered in 1942. It is caused by the presence of an extra X chromosome, resulting in XXY, as opposed to XY. With only one in six men who have Klinefelter’s ever diagnosed, even though symptoms often emerge during puberty, it may be one of the leading unexplored causes of infertility. Now, the first clinic in the UK to deal solely with Klinefelter’s has opened at Guy’s hospital in London – and its clinicians believe it could revolutionise its treatment and diagnosis. © 2019 Guardian News & Media Limited

Keyword: Sexual Behavior
Link ID: 26539 - Posted: 08.26.2019

By James Gorman Here are three good things about gulls: They are devoted parents. Males share child care equally with females. That includes sitting on the eggs during incubation. And they have figured out a way — actually many ways — to survive in a harsh and unforgiving world. Some eat clams, some eat fish, some are attracted to landfills. Of course, a few will divebomb you at the beach or boardwalk to steal a French fry, or the cheese on your cracker, or an entire slice of pizza. The beach pirate approach to survival is, of course, where humans and gulls clash. And the outcry from humans is almost as loud and outraged as the cries of the gulls themselves. Several recent news articles have chronicled the predations of gulls and some possible remedies. Ocean City, N.J., is bringing in hawks, and some scientists have suggested staring directly at gulls to fend them off. Though that is hard to do when the birds sneak up behind you as you are putting cheese on a cracker. There are some reports of more serious trouble. In England, a woman said a gull carried off her Chihuahua, and in Russia a pilot was hailed as a hero for safely landing his plane after a collision with a flock of gulls. In the New York area, thousands of birds, including gulls, have been killed in the decade since the Miracle on the Hudson crash to clear the skies for airplanes, without an apparent reduction in bird strikes. But it’s at the beach where tempers flare most predictably. And in times like these, with heightened human-gull tensions, very little has been written about the gulls’ point of view. Is there a Lorax who speaks for the gulls? Admittedly, gulls have quite a strong voice of their own, it’s just that it’s pretty unintelligible to most of us. An ornithologist would seem to be the obvious choice. They like birds. I called Christopher Elphick at the University of Connecticut. He spends a lot of time studying sparrows, but has a soft spot for gulls. © 2019 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 26537 - Posted: 08.24.2019

By Gretchen Reynolds For women with serious depression, a single session of exercise can change the body and mind in ways that might help to combat depression over time, according to a new study of workouts and moods. Interestingly, though, the beneficial effects of exercise may depend to a surprising extent on whether someone exercises at her own pace or gets coaching from someone else. Already, a wealth of recent research tells us that exercise buoys moods. Multiple studies show that physically active people are more apt to report being happy than sedentary people and are less likely to experience anxiety or depression. In a few experiments, regular exercise reduced the symptoms of depression as effectively as antidepressant medications. But science has yet to explain how exercise, a physical activity, alters people’s psychological health. Many exercise scientists speculate that working out causes the release of various proteins and other biochemical substances throughout our bodies. These substances can enter the bloodstream, travel to our brains and most likely jump-start neural processes there that affect how we feel emotionally. But it has not been clear which of the many substances released during exercise matter most for mental health and which kinds of exercise prompt the greatest gush in those biochemicals. Those open questions prompted Jacob Meyer, an assistant professor of kinesiology at Iowa State University in Ames, to start considering endocannabinoids and the runner’s high. As the name indicates, endocannabinoids are self-produced psychoactive substances, similar to the psychoactive compounds in cannabis, or marijuana. Created in many of our body’s tissues all the time, endocannabinoids bind to specialized receptors in our brains and nervous systems and help to increase calm and improve moods, among other effects. © 2019 The New York Times Company

Keyword: Depression; Sexual Behavior
Link ID: 26522 - Posted: 08.21.2019

Statistics Canada says Canadian men are almost twice as likely to use cannabis as women. New data from the National Cannabis Survey today shows 16 per cent of Canadians over 15 years old report using pot in April, May or June. That's down slightly from 17.5 per cent in the first three months of the year. Almost five million Canadians consumed cannabis in some form during the three month period. One quarter of men, and 16 per cent of women, reported they plan to consume it in the next three months. The survey suggests men are more likely to use cannabis daily or weekly than women, and are also more likely to use it for non-medicinal purposes. About four in 10 marijuana users say they bought cannabis illegally. Smoking the drug remains the most common way of consuming it, with 68 per cent of men and 62 per cent of women consumers choosing this method. At 14 per cent, women were almost three times more likely than men (five per cent) to have consumed cannabis through "other methods," including edible and topical variants. Recreational marijuana became legal in Canada last October and Statistics Canada is tracking consumption habits every three months. ©2019 CBC/Radio-Canada.

Keyword: Drug Abuse; Sexual Behavior
Link ID: 26506 - Posted: 08.16.2019

By Katie Camero For humans, slight variations in temperature don’t mean much. But for some turtles, they mean the difference between whether embryos come out male or female. Now, scientists have evidence that these embryos have some power over their sexual destiny: By moving to slightly warmer or cooler spots inside their eggs, freshwater turtle embryos can help determine their own sex. Not everyone is convinced. But if the new finding holds, this behavior could potentially save some turtle species from extinction by balancing their sex ratios. A reptile’s sex depends on hormones produced during development. For crocodiles, many fish, some lizards, and most turtles, those hormones in turn depend on external temperatures. Cooler temperatures typically lead to more males, and warmer temperatures generally lead to more females. That means a shift of just 2°C can make all of the offspring one sex. As average global temperatures rise, such a strategy could doom some species, including the already-endangered Chinese pond turtle (Mauremys reevesii). As weather warms, warmer eggs produce more and more females—leaving them fewer males to mate with. Wondering whether turtle embryos could respond to rapidly changing temperatures, scientists from the Chinese Academy of Sciences in Beijing examined the behavior of the Chinese soft-shelled turtle (Pelodiscus sinensis). They discovered that the embryos could in fact move between cooler and warmer spots inside their paperclip-size eggs, they reported in 2011 in the Proceedings of the National Academy of Sciences. © 2019 American Association for the Advancement of Science.

Keyword: Sexual Behavior
Link ID: 26477 - Posted: 08.02.2019

By Knvul Sheikh It’s a myth that black widow female spiders always kill and consume their mates. But courtship remains perilous for males, cannibalism or no. The terrain, navigated in the dark, is challenging. The female’s web releases come-hither pheromones, but only about 12 percent of prospective males manage to reach it. And once there, they can expect to face male rivals competing to pass their genes on to the next generation. Usually, this results in wild displays of machismo. The males slash the female’s webs to make them less enticing to others. They deposit “mating plugs” in the female’s body to block rival sperm. Why not simply avoid the competition and seek out females’ webs empty of other males? But male black widows actually seem to thrive on the competition, according to a study published Wednesday in the Proceedings of the Royal Society B: Biological Sciences. Researchers found that male black widows find potential mates faster by following the silk trails left behind by other males. “Males have to race to find females,” said Catherine Scott, an arachnologist at the University of Toronto Scarborough in Canada and the study’s lead author. “It makes sense for them to try to use all the tricks they can to find females as soon as possible, even if there are other males that have already found her.” If a male arrives an hour or two late at a female’s web, he still has a chance to interrupt the courting rituals of other males, and could still be the first to mate with the female, Ms. Scott said. Males typically make their way to a rendezvous by following female pheromones back to their source. But those signals must be at just the right distance, and uninterrupted by shifting winds and other factors. © 2019 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 26476 - Posted: 08.01.2019