Evolution leads autism and other conditions to occur much more frequently in boys

HAMILTON, ON, March 3, 2021 – Evolutionary forces drive gender imbalance in many health conditions, including autism, a team of genetic researchers has concluded.

The human genome has evolved to favor the inheritance of very different traits in men and women, which in turn makes men more vulnerable to a number of physical and mental health ailments, say that the researchers are responsible for a new paper published in the Journal of molecular evolution.

Their analysis shows that while certain conditions only occur in women (breast cancer and ovarian cancer, for example), or are much more common in women (such as multiple sclerosis), men are more likely for all medical conditions and, as a result, on average die faster than women.

“Our cells have memories and carry a collection of the changes that our ancestors have seen over millions of years,” said Rama Singh, McMaster’s professor of biology who co-wrote the paper with his son , Karun Singh, associate professor of neuropathology at the University of Toronto, and Shiva Singh (unrelated), professor of biology at Western University.

The researchers looked at autism as an example of the general tendency for men to develop medical conditions more often than women. Although women and men inherit the same genetic blueprints from their parents, the way in which these blueprints are expressed is quite different, depending on gender.

“If women and men were more different, they would be different sexes,” mocks Rama Singh, the paper’s corresponding author.

The researchers ’work is part of a growing trend toward studying genomic effects on health, using hereditary patterns to understand and project health effects on individuals and populations.

“One of the reasons I think this is interesting is that it offers a view that is not well represented in the medical literature,” says Karun Singh. “This is a great example of the perspective that evolutionary geneticists and biologists can contribute to health research.”

The paper examines hereditary forces that have evolved over millions of years, favoring partner selection and reproduction in the early years of male sex maturity at the expense of long-term well-being.

Although human behavior toward companion selection has changed, these genetic traits are still expressed in the health and development of today’s men.

Women, the researchers say, tend to live longer and are less vulnerable to most health conditions because their genetic makeup has evolved in response. on the unhealthy characteristics of the male genome, creating better immunity and greater longevity.

Understanding human health through the lens of genomics can and should guide the search for remedies and prevention, the researchers say.

While the origins of mental health conditions are more complex, they are influenced by the same evolutionary factors, the authors say. Women are more likely to be depressed and anxious, for example, while men are more likely to develop antisocial disorders.

In autism, male-female imbalance is particularly pronounced. Boys are as much as four times more likely to develop autism and are also more likely to develop severe symptoms.

Evolution seems to have created a higher threshold that will protect more women from developing the condition, the authors say.

While autism is not just a result of inherited traits, boys seem to be more likely to acquire traits that make them more vulnerable to environmental, developmental, and other factors, creating more pathways that can lead to autism.

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