A new study shows that the human genome has been subject to selection pressures favouring different characteristics in females and males, which makes males more susceptible to a variety of health conditions.
Genetic sex differences have long been known to have an impact on health. On balance, while females have certain conditions unique to them (eg, cervical cancer), or are more prone to (eg, multiple sclerosis), males are more prone to certain medical conditions, bringing down their average life expectancy compared to women.
Their research adds to a body of knowledge on genomic influences on health, which can map hereditary traits onto individuals and populations to guide healthcare. Looking at health conditions through the lens of genomics can help clinicians to better understand them and guide development of new treatments.
“Our cells have memories and they carry the accumulation of all the changes our ancestors have experienced over millions of years,” said Rama Singh, a McMaster biology professor who wrote the paper with his son, Karun Singh, an associate professor of neuropathology at the University of Toronto, and Shiva Singh (no relation), a biology professor at Western University.
The researchers focussed on autism, which is a good example of the way men and women develop medical conditions differently; though they inherit the same sets of genes from the parents, the expression of those genes differs greatly by sex.
Though human behaviour regarding mate selection has changed, those genetic characteristics remain and continue to be expressed in the health and development of modern men.
The male genome has been shaped over millions of years, and favours reproduction in the early years of male maturity to pass on genes, at the expense of genetic well-being in the long term.
Women are less vulnerable to most health conditions, living longer than men because their genomes have evolved to protect against unhealthy traits in the male genome, resulting in better immunity and more longevity.
The same forces shaping human selection also apply to mental health, even though it is complex. Women are more prone to anxiety and depression, while men are more prone to anti-social disorders.
“If women and men were any more different, they would be different species,” joked corresponding author, Prof Karun Singh.
Male-female imbalance is especially pronounced in autism, with being up to four times more likely to have some form of autism, and are also more likely to have severe symptoms. Evolution has resulted in a higher threshold, protecting females from developing the condition.
Although autism is not solely the result of inherited characteristics, it does appear that boys are more likely to develop it as a result of other inhertied characteristics rendering them more vulnerable to environmental, developmental and other factors that give rise to autism.
“One of the reasons I think this is interesting is that it offers a perspective that is not well represented in the medical literature. This is a really good example of the perspective that geneticists and evolutionary biologists can add to health research,” said Prof Karun Singh.
Source: News-Medical.Net
Journal information: Singh, R. S., et al. (2021) Origin of Sex-Biased Mental Disorders: An Evolutionary Perspective. Journal of Molecular Evolution. doi.org/10.1007/s00239-021-09999-9.
