Older Dads Pass Down More Mutations: The Implications
A study this week reported that older men pass on more new mutations to their offspring than do younger men, a fact that could help explain higher rates of disorders such as autism, schizophrenia and others in kids born of older fathers.
The same week, another article by the same group calculated that the mutation rate in fathers doubles between age 20 and age 58.
Why fathers more than mothers? Because many of these mistakes happen as cells divide, and as we get older the rate of errors rises. Since sperm is made all the way through the man’s life and all eggs are pretty much ready before a woman is even born, the difference makes sense.
Bad news? On a personal level, yes, since a DNA mutation — should it have an effect at all — is more likely to have a negative effect than a positive one.
And on a societal level, it could be bad too, says Alexey Kondrashov, an evolutionary geneticist at the University of Michigan who wrote a commentary accompanying Stefansson’s report. He’s worried about an issue that has been discussed (often very contentiously) since Charles Darwin’s time: an accumulation of mutations with negative effects in our species.
“Modern human populations are subject to many fewer selection pressures than has been the case throughout human evolutionary history,” Kondrashov writes. “Because deleterious mutations are much more common than beneficial ones, evolution under this relaxed selection will inevitably lead to a decline in the mean fitness of the population.”