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Sex Differences and Vulnerability: How the Male-Female Divide Affects Health

By: , Posted on: September 15, 2015

An interview with controversial evolutionary psychologist Professor David Geary throws up questions about the role of gender in health and well-being.

This article originally appeared on The Guardian. Click here to read the original article or continue reading below:

Recently, I met evolutionary psychologist Professor David Geary at the Wellcome Collection’s ‘Institute of Sexology’ exhibition. The exhibition focuses on how the practice of sex research has shaped our attitudes towards sexual behaviour and identity, and it seemed a good time to talk to Geary about his sometimes controversial views on sex differences, and his new work, the Evolution of Vulnerability.

“People talk about cultural factors creating sex differences, I think it’s the other way around, there’s pressure to dis-confirm the way people are. Cultural hype tries to make the sexes more alike, this is stressful for boys and girls and men and women,” explained Geary.

Sex specific features are evidenced from birth. For example, it has been shown that on average baby girls prefer looking at faces, while average baby boys prefer abstract shapes. Such biological sex differences are considered hard-wired and can be behavioural, anatomical and cognitive.

Anatomical difference can manifest as ornamentation, such as the lion’s mane, stag’s antlers, long, iridescent peacock feathers and, in humans, the female breast and male height. Unlike naturally selected traits, sex differences are selected for by the opposite sex.

Sex differences are also malleable, having evolved so resiliency to poor environmental conditions or social stressors is reflected in their expression. An animal bereft of good genes will be susceptible to parasites, have poor ornamentation, low social status, a shorter lifespan and may never breed.

When it comes to researching human behavioural sex differences, however, the hard-wired element frequently causes controversy, much to Geary’s frustration.

“The PC-types have been intimidating and very effective in suppressing dissent. Other academics don’t want the hassle of being called ‘sexist’. People are afraid to speak out! Fortunately, I’ve been blessed with a sufficient amount of social insensitivity not to worry too much.”

Read more from David Geary on SciTech Connect: Like It or Not, Math Matters

Armed with his new vulnerability hypothesis, which reframes the notion of ‘male vulnerability’, Geary’s poised, yet again, to stir up controversy.

Previous male naturalists focused on males, and vulnerabilities of girls and women were overlooked, says Geary. “What’s interesting is sex-specific vulnerabilities. Not only are male physical traits vulnerable, but cognitive and social traits are too and these are different to traits vulnerable in females.”

Over the years language studies have revealed a female advantage, and experimental psychology identified a male advantage in spatial ability, but no one has recognised that the phenomenon of sexually selected traits being sensitive to stressors can actually be used to detect health and welfare problems.

For example, some studies have shown that premature baby girls will grow up to suffer greater language deficits than premature boys, whereas boys exposed to certain prenatal toxins will suffer greater deficits to spatial skills than girls similarly exposed, but because sex differences were never the original focus of the research no one, until Geary, has united these sex specific developmental problems and placed them in evolution’s bigger picture. Geary explains, “Sexually selected traits are the first to go; for example, low level exposure to prenatal toxins will affect play in boys but not their IQ: if you don’t measure the right thing you will fail to detect underlying problems.”

In light of this, I asked Geary to review the WHO’s European campaign, Health2020, to see what his hypothesis could add. “There’s good things, but they’re saying sex differences are not important and what’s important is socialisation and culturation, which means they’re going to miss sex-specific sensitivities to stressors and by not considering these they may underestimate the negative effects. By taking sex differences seriously, the WHO could design studies that will provide a more thorough and complete understanding of the factors that undermine wellbeing and the ability to achieve one’s full potential.”

But some gender specialists insist theories on sex differences are exaggerated and harmful to women. Professor Alice Eagly, of Northwestern University, declined to contend with Geary’s new hypothesis but commented, “Chronic inequality affects the psychology of women, just as men’s greater status and privilege affect their psychology.”

But life in the womb can’t be socially conditioned and, rhetorically, Geary queried how any amount of societal male privilege could result in making the development of unborn baby boys’ “spatial abilities or play behaviour susceptible to prenatal toxins but leave unaffected those of girls?”

Considering the Wellcome gives £700M annual budget for bio-medical research, Geary listed the areas he would focus on. “Poor nutrition, chemotherapy side effects, anorexia, alcohol abuse, Alzheimer’s, among others, are informed by this approach. Studying sex specific vulnerabilities would involve many of the types of studies already done, but with an expansion of outcomes assessed and a focus on sex differences. The last chapter of the Evolution of Vulnerability explains how.”

Geary’s book breaks down vulnerable traits and highlights measures for different stressors. From female emotional reciprocity across lifespan and female pelvic growth in adolescence to male peer group density across lifespan and boys’ femur and ulna growth, any subtle changes indicating further investigation is needed.

Geary is the first academic to frame biological sex differences in terms of their vulnerability, and he believes this approach could transform science and medicine. The vulnerability hypothesis potentially has interdisciplinary applications: it’s not just health and wellbeing practices that can benefit. Social work is another area that could potentially be enriched if sex differences, particularly inparental investment, were fully assimilated. But in Geary’s view, to get the most out of the research done so far, politically correct obfuscation must go.

Professor Timothy Crippen, a sociologist from the University of Mary Washington agrees. “A sizeable number of social scientists remain reluctant to engage with the evolutionary sciences and misinformed criticisms are thinly veiled expressions of ideological angst. Controversy surrounding scholars, such as David Geary, eventually will recede.”

Their view is that stymying this area by denying sex differences won’t help women break through the glass ceiling because, ‘difference’, doesn’t mean better or worse. In fact, difference is essential for diversity and species survival. Geary’s focus is the paradoxical male and female prime, where strengths invert, becoming weaknesses.

“There’s a fear acknowledging differences will undermine women’s economic progress. But how we govern ourselves today and the evolutionary forces that acted on our ancestors are different issues. Our world is different, but what our ancestors went through still reflects in our bodies and minds. The US spends vast sums on interventions to change social stereotyping, but if you ignore sex differences I guarantee sex inequality will continue.”

About the Author

david gearyDavid C. Geary is a cognitive developmental and evolutionary psychologist at the University of Missouri. He has wide ranging interests but his primary areas of research and scholarly work are children’s mathematical cognition and learning and Darwin’s sexual selection as largely but not solely related to human sex differences. Professor Geary directed a 10-year longitudinal study of children’s mathematical development from kindergarten to ninth grade, with a focus on identifying the core deficits underlying learning disabilities and persistent low achievement in mathematics. The study was funded by the National Institutes of Health (US), including through a MERIT award to professor Geary.

Professor Geary’s interests in evolution are reflected in two of his other books published by the American Psychological Association, The origin of mind: Evolution of brain, cognition, and general intelligence (2005), and Male, female: The evolution of human sex differences (1998, 2010 second edition). The corresponding empirical work ranges from the study of changes in brain volume during hominid evolution to human mate choices to hormonal responses to simulated (video game) competition. Professor Geary’s current interests in this area follow from several of his collaborative studies on the effects of prenatal toxin exposure on sex differences in cognition and behavior in mice. Specifically, traits related to Darwin’s sexual selection are often exaggerated relative to other traits. These would include, for example, the bright plumage of the males of many species of bird that in turn is a good indicator of their behavioral and genetic health. These traits are particularly sensitive to environmental disruption, even in healthy individuals. Professor Geary’s in progress book, The evolution of vulnerability, is focused on these traits in humans and how they can be used to identify at-risk populations and individuals.

evolution of vulnerability

David Geary is the author of several books including the recently released Evolution of Vulnerability: Implications for Sex Differences in Health and Development. The book frames the evolution of sex-specific, condition-dependent traits in ways that will help researchers better understand, predict, and prevent human vulnerabilities. The book is available for purchase on the Elsevier Store. Use discount code “STC215″ at checkout and save up to 30% on your very own copy!

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