The tick-tock of the biological clock rings in the ears of many women as they approach their mid- to late thirties and into their forties. For some, the sound is deafening and anxiety-inciting. For others, it barely resonates until someone else, ruefully minding your business, brings it up. Regardless of how each woman views it, the term “biological clock” has become so sex-specific as to make “female” an unnecessary prefix. All the while, men generally feel unburdened by a clock—so long as a man gets around to it before he can cash his first Social Security check and can find a willing mate, the kids will come, and his lineage shall be strong and plentiful. Or so it was once thought.
It would be unfair if it were true. The biological bell tolls for both women and men, albeit in different ways. Whereas women are at greater risk for infertility and giving birth to babies with Down syndrome as they age, men over thirty-five face an increased likelihood of bearing a child with abnormalities. Several papers produced by researchers from the United States and the United Kingdom suggest that the older the men are, regardless of their socioeconomic status and the age of the mother, the more likely they are to conceive children with autism, bipolar disorder, and schizophrenia.
Men on the Clock
While all of this research might be novel, its concepts are not. As early as 1912 scientists (the first being a gynecologist by the name of William Weinberg, a huge contributor to the field of genetics) proposed a link between birth disorders and the increasing age of the father. By 1955, L.S. Pearson codified the idea: his copy-error hypothesis stated that sperm were much more likely to experience mutations than eggs, thereby leading to increased likelihood of birth defects attributable to the father’s older age. Leading geneticist James F. Crow explains why males have a higher mutation rates than females in his 1997 review in the Proceedings of the National Academy of Sciences:
“The most obvious explanation lies in the much greater number of cell divisions in the male germ line than in the female germ line. In the female, the germ cell divisions stop by the time of birth ... In the male, cell divisions are continuous and many divisions have occurred before a sperm is produced.”
