As men age, so do their sperm. According to new research, sperm is also mutating with age. That in turn, actually increases the chances of fathering a child with a genetic disorder.

New Scientist reports on research by Anne Goriely from the University of Oxford suggesting that these mutations cause stem cells in the testicles to divide abnormally, which results in an increasing proportion of mutant sperm as men age and an ever growing chance of a mutant sperm fertilizing an egg.

Some mutations are tied to rare conditions like the Apert syndrome, where childhood development falters resulting in fused toes and fingers. It is also believed that mutations could give rise to common disorders like autism and schizophrenia as well. It could explain why those conditions seem increasingly common these days.

Researchers believe a "selfish sperm" effect could make these problems spread:
What if some mutations give the stem cells a selective advantage by making them divide abnormally and produce more than one daughter spermatogonium each? One such "selfish spermatogonium" arising in the testicles of a young man could give rise to thousands of these mutant stem cells after a decade or two, each carrying a copy of the mutated gene. The proportion of mutant sperm would increase at an exponential rate, rather than linearly.
What we do know for sure is that younger sperm seem to be healthier sperm. Perhaps its time we became fathers earlier? [New Scientist]