Evolutionary forces explain the gender imbalance in the occurrence of autism and other health conditions
Evolutionary forces lead to an apparent gender imbalance in the occurrence of many health problems, including autism, a team of genetic researchers found.
The human genome has evolved to favor the inheritance of very different traits in men and women, which in turn makes men more prone to a variety of physical and mental illnesses, say the researchers, responsible for a new paper published in the Journal of Molecular Evolution are responsible.
Their analysis shows that while there are certain diseases that occur only in women (e.g. cervical cancer and ovarian cancer) or much more common in women (e.g. multiple sclerosis), men are more prone to disease overall, on average die earlier than women.
“Our cells have memories and they carry the accumulation of all the changes our ancestors have experienced over millions of years,” says Rama Singh, a McMaster biology professor who works with his son Karun Singh, an adjunct professor of neuropathology at the University, has written University of Toronto and Shiva Singh (no relationship), professor of biology at Western University.
The researchers looked at autism as an example of the general tendency for men to develop diseases more often than women. Although women and men inherit the same genetic blueprints from their parents, the way those blueprints are expressed varies widely depending on their gender.
“If women and men were more different, they would be different types,” jokes Rama Singh, the newspaper’s author.
The researchers’ work is part of a growing movement to study genomic influences on health, using hereditary patterns to understand and project health effects on individuals and populations.
One of the reasons I find this interesting is because it offers a perspective that is not well represented in the medical literature. This is a really good example of the perspective geneticists and evolutionary biologists can add to health research. “
Karun Singh, Associate Professor of Neuropathology, University of Toronto
The paper examines hereditary forces that have evolved over millions of years and favor selection and reproduction of partners in the early years of male sexual maturity at the expense of longer-term well-being.
Although human behavior in relation to partner selection has changed, these genetic traits remain and are still expressed in the health and development of modern men.
Women, the researchers say, tend to live longer and are less prone to most health conditions because their genetic makeup evolved in response to the unhealthy properties of the male genome, resulting in better immunity and longer lifespans.
Understanding human health through the lens of genomics can and should guide the search for treatments and preventions, say the researchers.
Although the origins of mental illness are more complex, they are influenced by the same evolutionary factors, the authors say. For example, women are more prone to depression and anxiety, while men are more likely to develop antisocial disorders.
The imbalance between men and women is particularly pronounced in autism. Boys are up to four times more likely to have some form of autism and more likely to have severe symptoms.
Evolution appears to have created a higher threshold that protects more women from developing the disease, say the authors.
While autism is not solely due to inherited traits, it seems that boys are more likely to inherit traits that make them more vulnerable to environmental, developmental, and other factors, and create more pathways that can lead to autism.
Singh, RS et al. (2021) Origins of Gender-Specific Mental Disorders: An Evolutionary Perspective. Journal of Molecular Evolution. doi.org/10.1007/s00239-021-09999-9.