Men Have Biological Clocks, Too–and They Tick Just as Loudly

Children conceived by women over 35 are known to have and increased risk of being born with Down syndrome and a variety of other birth defects. But a brand new study just revealed that the father’s age is important too. Children of older fathers are at increased risk of developing autism and schizophrenia.

It all has to do with the number of genetic mutations passed through to children by either the mothers’ eggs or the father’s sperm. It turns out that mothers, regardless of their age, contribute about 15 mutations to their children. But for men, the number of mutations increases by about two per year. A 20-year old man contributes about 25 genetic mutations, while a 40-year old has about 65.

Now, I know that the word “mutation” conjures up all sorts of images of X-men and mutant Ninja turtles. But it’s important to remember that most mutations are completely harmless.  “All areas of the human genome were a mutation once upon a time, so all human variety is down to a mutation,” says Kari Stefansson, senior author of the study, which was published in the journal Nature. Mutations are responsible for hair and eye color, the size of your nose, whether you have long ear lobes or none at all, and so on. 

Still, going from 25 mutations to 65 sounds pretty scary. Until you consider the real numbers. “There are three billion letters in the DNA code of humans and the numbers of mutations detected in this study are in the dozens,” said Professor Darren Griffin, a geneticist at Kent University, in an interview with The Daily Telegraph.  “The observed approximate doubling of mutation rate between the ages of 20 and 40 (when most fathers are actively reproducing) is certainly clinically noteworthy but not realistically likely to deter more mature fathers from having children.”

Some people are responding to this research by suggesting that young men bank their sperm as a way of reducing the risk of disease in their future children. But others aren’t so sure. And given the infinitesimally small risk that a genetic mutation would lead to a health problem, it’s unlikely that sperm banking will become a routine procedure for young men who think they might want to become fathers later in life.

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