Tag Archives: #female

Males and Females Are Programmed Differently in Terms of Sex (Biology)

The evolutionary biologist Olivia Judson wrote, ‘The battle of the sexes is an eternal war.’

Males and females not only behave differently in terms of sex, they are evolutionarily programmed to do so, according to a new study from Oxford, which found sex-specific signals affect behaviour.

Males and females not only behave differently in terms of sex, they are evolutionarily programmed to do so

The new study from Oxford’s Goodwin group from the Department of Physiology, Anatomy and Genetics says, despite sharing very similar genome and nervous system, males and females ‘differ profoundly in reproductive investments and require distinct behavioural, morphological, and physiological adaptations’.

The team argues, ‘In most animal species, the costs associated with reproduction differ between the sexes: females often benefit most from producing high-quality offspring, while males often benefit from mating with as many females as possible. As a result, males and females have evolved profoundly different adaptations to suit their own reproductive needs.’

Males and females have evolved profoundly different adaptations to suit their own reproductive needs

The question for the researchers was: how does selection act on the nervous system to produce adaptive sex-differences in behaviour within the bounds set by physical constraints, including both size and energy, and a largely shared genome?

Today’s study offers a solution to this long-standing question by uncovering a novel circuit architecture principle which allows deployment of completely different behavioural repertoires in males and females, with minimal circuit changes. 

The research team, led by Dr Tetsuya Nojima and Dr Annika Rings, found that the nervous system of vinegar flies, Drosophila melanogaster, produced differences in behaviour by delivering different information to the sexes.

In the vinegar fly, males compete for a mate through courtship displays; thus, the ability to chase other flies is adaptive to males, but of little use to females. A female’s investment is focused on the success of their offspring; thus, the ability to choose the best sites to lay eggs is adaptive to females.

When investigating the different role of only four neurons clustered in pairs in each hemisphere of the central brain of both male and female flies, the researchers found the sex differences in their neuronal connectivity reconfigures circuit logic in a sex-specific manner. In essence, males received visual inputs and females received primarily olfactory (odour) inputs. Importantly, the team demonstrated that this dimorphism leads to sex-specific behavioural roles for these neurons: visually guided courtship pursuit in males and communal egg-laying in females. 

In essence, males received visual inputs and females received primarily olfactory (odour) inputs

These small changes in connectivity between the sexes allowed for the performance of sex-specific adaptive behaviour most suited to these reproductive needs through minimal modifications of shared neuronal networks. This circuit principle may increase the evolvability of brain circuitry, as sexual circuits become less constrained by different optima in male and females.

And it works, the study says, ‘Ultimately, these circuit reconfigurations lead to the same end result—an increase in reproductive success.

‘Our findings suggest a flexible strategy used to structure the nervous system, where relatively minor modifications in neuronal networks allow each sex to react to their surroundings in a sex-appropriate manner.’

Furthermore, this is the first time a firm link between sex-specific differences in neuronal networks have been explicitly linked to behaviour.

According to Professor Stephen Goodwin, ‘Previous high-profile papers in the field have suggested that sex-specific differences in higher-order processing of sensory information could lead to sex-specific behaviours; however, those experiments remained exclusively at the level of differences in neuroanatomy and physiology without any demonstrable link to behaviour. I think we have gone further as we have linked higher-order sexually dimorphic anatomical inputs, with sex-specific physiology and sex-specific behavioural roles.’

We have linked higher-order sexually dimorphic anatomical inputs, with sex-specific physiology and sex-specific behavioural roles

Professor Stephen Goodwin

The researchers maintain ‘evolutionary forces’ have driven these adaptations, ‘Drosophila, males compete for a mate through courtship displays, while a female’s investment is focused on the success of their offspring.’

They conclude, ‘In this study, we have shown how a sex-specific switch between visual and olfactory inputs underlies adaptive sex differences in behaviour and provides insight on how similar mechanisms maybe implemented in the brains of other sexually-dimorphic species.’

Featured image: Sex differences in vinegar flies’ brains’ neural connectivity reconfigures circuit logic in a sex-specific manner. Males receive visual inputs and females’ olfactory (odour) inputs. © University of Oxford

The full paper, A sex-specific switch between visual and olfactory inputs underlies adaptive sex differences in behaviour, joint-first authored by Dr Tetsuya Nojima and Dr Annika Rings, is available to read in Current Biology.


Provided by University of Oxford

Early Big-game Hunters Of The Americas Were Female, Researchers Suggest (Archeology / Anthropology)

For centuries, historians and scientists mostly agreed that when early human groups sought food, men hunted and women gathered. However, a 9,000-year-old female hunter burial in the Andes Mountains of South America reveals a different story, according to new research conducted at the University of California, Davis.

Illustration of female hunter depicting hunters who may have appeared in the Andes 9,000 years ago. ©Matthew Verdolivo, UC Davis IET Academic Technology Services.

“An archaeological discovery and analysis of early burial practices overturns the long-held ‘man-the-hunter’ hypothesis,” said Randy Haas, assistant professor of anthropology and the lead author of the study, “Female Hunters of the Early Americas.” It was published today (Nov. 4) in Science Advances.

“We believe that these findings are particularly timely in light of contemporary conversations surrounding gendered labor practices and inequality,” he added. “Labor practices among recent hunter-gatherer societies are highly gendered, which might lead some to believe that sexist inequalities in things like pay or rank are somehow ‘natural.’ But it’s now clear that sexual division of labor was fundamentally different — likely more equitable — in our species’ deep hunter-gatherer past.”

In 2018, during archaeological excavations at a high-altitude site called Wilamaya Patjxa in what is now Peru, researchers found an early burial that contained a hunting toolkit with projectile points and animal-processing tools. The objects accompanying people in death tend to be those that accompanied them in life, researchers said. It was determined that the hunter was likely female based on findings by the team’s osteologist, James Watson of The University of Arizona. Watson’s sex estimate was later confirmed by dental protein analysis conducted by UC Davis postdoctoral researcher Tammy Buonasera and Glendon Parker, an adjunct associate professor.

Revealing a broader pattern

The surprising discovery of an early female hunter burial led the team to ask whether she was part of a broader pattern of female hunters or merely a one-off. Looking at published records of late Pleistocene and early Holocene burials throughout North and South America, the researchers identified 429 individuals from 107 sites. Of those, 27 individuals were associated with big-game hunting tools — 11 were female and 15 were male. The sample was sufficient to “warrant the conclusion that female participation in early big-game hunting was likely nontrivial,” researchers said. Moreover, the analysis identified the Wilamaya Patjxa female hunter as the earliest hunter burial in the Americas.

This illustration from the study shows tools recovered from the burial pit floor including projectile points (1 to 7), unmodified flakes (8 to 10), retouched flakes (11 to 13), a possible backed knife (14), thumbnail scrapers (15 and 16), scrapers/choppers (17 to 19), burnishing stones (17, 20, and 21), and red ocher nodules (22 to 24). ©Randy Haas/UC Davis

Statistical analysis shows that somewhere between 30 to 50 percent of hunters in these populations were female, the study said. This level of participation stands in stark contrast to recent hunter-gatherers, and even farming and capitalist societies, where hunting is a decidedly male activity with low levels of female participation, certainly under 30 percent, Haas explained.

The study was conducted in collaboration with multiple UC Davis labs. Parker, a forensic expert in the Department of Environmental Toxicology, helped determine sex through a proteomic technique he recently developed. In Professor Jelmer Eerkens’ lab, Jenny Chen, an undergraduate researcher at the time of the study, discovered the distinct isotopic signature of meat consumption in the bones, further supporting the conclusion that the Wilamaya Patjxa female was a hunter.

While the research answers an old question about sexual division of labor in human societies, it also raises some new ones. The team now wishes to understand how sexual division of labor and its consequences in different times and places changed among hunter-gatherer populations in the Americas.

Reference : Randall Haas, James Watson, Tammy Buonasera, John Southon, Jennifer C. Chen, Sarah Noe, Kevin Smith, Carlos Viviano Llave, Jelmer Eerkens, Glendon Parker, “Female hunters of the early Americas”, Science Advances, Vol. 6, no. 45, eabd0310, 2020. DOI: 10.1126/sciadv.abd0310 link: https://doi.org/10.1126/sciadv.abd0310

Provided by University of California Davis

How An Egg Cell’s “Operating Manual” Sets The Stage For Fertility? (Biology)

Genetic instructions immature egg cells go through step by step as they mature into functionality revealed in unprecedented detail.

Recently published work from Carnegie’s Allan Spradling and Wanbao Niu revealed in unprecedented detail the genetic instructions immature egg cells go through step by step as they mature into functionality. Their findings improve our understanding of how ovaries maintain a female’s fertility.

An illustration of gene expression underlying wave1 and wave2 follicle production. Each dot on the diagram mathematically summarizes the gene expression of individual ovarian helper cells that surround developing egg cells in two-dimensional gene space. Developing cells fall into clusters indicated by a common color and clusters are present in the ovary only at single developmental times (i.e. E14.5, E16.5, etc.) indicated for cells within the dashed zones. It can be seen that each time zone houses precisely two types of follicle cells, which were found to come from future wave 1 follicles (4, odd numbers >4) or wave 2 two follicles (even numbers >4). ©Figure is courtesy of Allan Spradling and Wanbao Niu. Underlying image purchased from Shutterstock. Composite created by Navid Marvi.

The general outline of how immature egg cells are assisted by specific ovarian helper cells starting even before a female is born is well understood. But Spradling and Niu mapped the gene activity of thousands of immature egg cells and helper cells to learn how the stage is set for fertility later in life.

Even before birth, “germ” cells assemble a finite number of cell clusters called follicles in a female’s ovaries. Follicles consist of an immature egg cell and some “helper” cells, which guide the egg through its maturation process. It is from a follicle that a mature egg cell bursts during ovulation.

“Follicles are slowly used up during a female’s reproductive lifespan and menopause ensues when they run out. Understanding what it takes for follicles to form and develop successfully, helps us learn how damaged genes or adverse environmental factors, including a poor diet, can interfere with fertility,” explained Spradling. “By documenting the follicle’s genetic operating manual, problems in egg development that might lead to birth defects –as a result of mutations or due to bad nutrition– can be better understood and reduced.”

Spradling and Niu sequenced 52,500 mouse ovarian cells at seven stages of follicle development to determine the relative expression of thousands of genes and to characterize their roles.

The study also illuminated how mammalian ovaries produce two distinct types of follicles and Spradling and Niu were able to identify many differences in gene activity between them.

The first, called wave 1 follicles, are present in the ovary even before puberty. In mice, they generate the first fertile eggs; their function in humans is poorly understood, but they may produce useful hormones. The second type, called wave 2 follicles, are stored in a resting state but small groups are activated to mature during a female’s hormonal cycle, ending in ovulation. The findings help clarify each type’s roles.

Spradling and Niu’s work and all its underlying data were published by Proceedings of the National Academy of Sciences.

“We hope our work will serve as a genetic resource for all researchers who study reproduction and fertility,” concluded Spradling.

References: Wanbao Niu and Allan C. Spradling, “Two distinct pathways of pregranulosa cell differentiation support follicle formation in the mouse ovary”, PNAS August 18, 2020 117 (33) 20015-20026; first published August 5, 2020; https://doi.org/10.1073/pnas.2005570117 link: https://www.pnas.org/content/117/33/20015

Provided by Carnegie Institute For Science

These Are The Differences Between Male And Female Narcissists (Psychology)

Narcissism isn’t cute. In fact, it can be flat-out destructive. But in order to protect yourself from it, you need to know what you’re looking for. According to research, the telltale signs of narcissism that you may have on your radar could be slightly off, depending on who you’re looking at. It turns out that narcissism has some distinct gender differences.

You know the major cues when it comes to spotting a narcissist: someone being totally full of themselves, completely self-absorbed, having no time for anyone else, and on and on. About 6 percent of Americans have narcissistic personality disorder, says a 2009 study. As described by the Mayo Clinic, narcissistic personality disorder is “a mental condition in which people have an inflated sense of their own importance, a deep need for excessive attention and admiration, troubled relationships, and a lack of empathy for others.” But that doesn’t quite cover everything. According to a 2016 meta-analysis published in the Psychological Bulletin, it’s not one-size-fits-all — there are differences between male and female narcissists.

The study looked at three decades of data from narcissism research that included more than 475,000 participants and found that men, on average, are more narcissistic than women. Regardless of age, men consistently scored higher in narcissism compared to the women studied. That could say more about society at large than you’d think.

“Narcissism is associated with various interpersonal dysfunctions, including an inability to maintain healthy long-term relationships, unethical behavior and aggression,” says lead author Emily Grijalva, Ph.D., an assistant professor of organization and human resources in the UB School of Management, in a statement. “At the same time, narcissism is shown to boost self-esteem, emotional stability and the tendency to emerge as a leader. By examining gender differences in narcissism, we may be able to explain gender disparities in these important outcomes.”

The team looked at three aspects of narcissism: leadership/authority, grandiose/exhibitionism, and exploitative/entitlement. They found that male and female narcissists don’t score evenly across these groups. Just because a man is more self-absorbed, let’s say, than a woman, it doesn’t mean he’s necessarily more narcissistic overall. Of these buckets, the researchers found the widest gap between men and women in the entitlement camp. This suggests that male narcissists are more likely to feel entitled to certain things and exploit people than female narcissists are.

The next biggest gender gap in narcissism was in leadership/authority. The third aspect, exhibitionism, had no gap at all. “Compared with women, men exhibit more assertiveness and desire for power,” Grijalva says, “but there was no difference in the exhibitionism aspect, meaning both genders are equally likely to display vanity or self-absorption.”

The team speculates that gender stereotypes may showcase or suppress which narcissistic traits either gender expresses. “Individuals tend to observe and learn gender roles from a young age, and may face backlash for deviating from society’s expectations,” Grijalva says. “In particular, women often receive harsh criticism for being aggressive or authoritative, which creates pressure for women, more so than for men, to suppress displays of narcissistic behavior.”

Bird Genes Are Multitaskers (Birds / Biology)

Scientists from the University of Sheffield have found that although male and female birds have an almost identical set of genes, they function differently in each sex through a mechanism called alternative splicing.

Males and females of the same bird species can be strikingly different. For example, in addition to fundamental differences in reproduction, the sexes can show profound variation in behavior, colouration, metabolism, disease incidence and life history. The team wanted to understand how these remarkable differences develop despite males and females sharing mostly the same DNA.

Thea Rogers, PhD student at the University of Sheffield and lead author of the study, said: “One notable example of differences between male and female birds is in the peafowl, peacocks have magnificent plumage, whereas the female peahen is relatively dull. The peacock’s long tail and bright colours evolved to help them attract mates, but having such eye-catching looks can come with negatives such as making them more noticeable to predators.

“Features like this are beneficial to the males but may not be beneficial for females, so birds must find a way to evolve different characteristics. We predicted that the secret to these differences must lie in understanding how the same genes are expressed and function differently in males and females.”

The team studied the genomes of multiple bird species to understand how they expressed these different qualities in males and females.

Genes encode proteins, large complex molecules which drive processes in the body and are responsible for the function and structure of the body’s tissues. Before genes can be used to make proteins, their DNA sequence is transcribed into RNA, an intermediary molecule that contains the instructions for making proteins.

The scientists found that males and females differ in how bits of RNA are stitched together, meaning that the same gene can produce a large number of distinct proteins and functions depending on which sex the gene is expressed in. This process is called alternative splicing.

Dr Alison Wright, a researcher at the University of Sheffield and senior author of the study, said: “It is likely that this genetic process is really important for generating biodiversity, not only in birds but across the whole animal kingdom.”

The study, published in Molecular Biology & Evolution, revealed hundreds of bird genes that use this method to enable the evolution of sex differences. The researchers showed that these genes have evolved remarkably rapidly as a result of the different selection pressures experienced by males and females.

This article is republished from eurekalert under common creative licenses.

Male Baboons That Have Close Female Friends Live Longer (Biology / Animals)

People who are more socially integrated or have higher socio-economic status live longer. Recent studies in non-human primates show striking convergences with this human pattern: female primates with more social partners, stronger social bonds or higher dominance rank all lead longer lives.

Drawing on 35 years of data, a new study of more than 540 baboons in Amboseli National Park in Kenya finds that male baboons that have close female friends have higher rates of survival than those who don’t.

However, it remains unclear whether social environments also predict survival in male non-human primates, as it does in men. This gap persists because, in most primates, males disperse among social groups, resulting in many males who disappear with unknown fate and have unknown dates of birth.

Researchers in this study presented a Bayesian model to estimate the effects of time-varying social covariates on age-specific adult mortality in both sexes of wild baboons. They compared how the survival trajectories of both sexes are linked to social bonds and social status over the life.

And what they found? They found that, parallel to females, male baboons who are more strongly bonded to females have longer lifespans. However, males with higher dominance rank for their age appear to have shorter lifespans. This finding brings new understanding to the adaptive significance of heterosexual social bonds for male baboons: in addition to protecting the male’s offspring from infanticide, these bonds may have direct benefits to males themselves.

References: Fernando A. Campos et al. Social bonds, social status and survival in wild baboons: a tale of two sexes, Philosophical Transactions of the Royal Society B: Biological Sciences (2020). DOI: 10.1098/rstb.2019.0621 link: https://royalsocietypublishing.org/doi/10.1098/rstb.2019.0621