'Cells have memories': Why men get certain ailments more than women
'If women and men were any more different, they would be different species,' says researcher
Men are more likely than women to experience numerous health conditions, including autism, infectious disease and immune system illness — and the reason, new McMaster University research shows, can be found in our genes.
In a new article published in the Journal of Molecular Evolution, Prof. Rama Singh and two co-authors posit that characteristics evolution has favoured in men give them "early fitness gains," but "at the cost of (later-life) fitness."
Women's evolution, they say, has fostered an internal resistance to the genes that mostly benefit men.
"If women and men were any more different, they would be different species," Singh said in a McMaster University press release this week.
The researchers focused on autism, which appears in males at four times the rate of females, to show how men develop medical conditions more often than women. But Singh says the findings relate to all other illnesses more common in men.
Singh says because men have more opportunity to reproduce than women — who have to wait around for nine months being pregnant — genetic mutations were more likely to favour men, particularly those that help them succeed at reproduction.
Further, "nature favours early reproduction. If two individuals are competing, the one who reproduces early gets access to resources early," he said.
Cells have memory
As such, genetic mutations will favour early reproduction at the expense of health later in a person's life. "Nature doesn't care," he said.
Meanwhile, female offspring who inherited those genes with "unhealthy characteristics" developed an internal response to block them, he says. Mutations that were beneficial to males but harmful to females were silenced by females, making their immune system more "elevated," protecting them from the diseases men experience, he said.
These hereditary forces have left their marks on our genes over millions of years of evolution, he says. Even as our behaviour has changed, the genetic traits of earlier humans still dictate much about our health.
"Our body has a history," he said.
"Our cells have memories."
Evolutionary biology as part of medical training
This research, which connects ancient humans with modern healthcare, shows that genetics should be considered when researchers search for treatments and ways of preventing disease, he says. It also highlights how important it is for today's doctors to be trained in evolution and genetics.
"We still graduate medical doctors without having taken any course in evolution … Part of the paper says it is about time for medical practitioners to learn something about evolution."
When older people visit a doctor, he said, "They will ask you, 'Is your mom living? Is your dad living?' What they're really asking is if any gene in the family makes you susceptible. But they are only going back one generation."
He says Shiva Singh plans to petition Western University to change its medical curriculum, but he hasn't done the same at McMaster. He says he hopes the paper speaks for itself in the scientific community.
"I hope by reading the paper, the medical people should be taking from it that genomic medicine is becoming more important."