Dan Eisenberg, Geoffrey Hayes and Christopher Kuzawa of Northwestern University have found that the older men are when they conceive their children, the longer those children’s telomeres are. Why does this matter? Telomere length is thought to have strong implications for longevity.
Telomeres are bits of noncoding DNA that cap the ends of our chromosomes like tassels. Because of the way DNA is replicated, each time a chromosome is copied a bit of the end is lost. That doesn’t matter as long as it’s only the telomeres that get shortened. Eventually, though, you run out of tassel and then the cell can no longer divide properly. Thus, having longer telomeres to start with allows a cell that many more productive divisions. In fact, telomeres in blood decrease by a predictable amount each year.
Diagram of a telomere at the end of a chromosome.
Telomere shortening is not irreversible. There are enzymes that lengthen telomeres. One such enzyme is particularly active in the testes, meaning that as a man ages, the telomeres in his sperm get longer. The researchers found that not only does a man’s age at the conception of his child determine the length of that child’s telomeres, but that the age of the paternal grandfather at the conception of the father also affects the eventual grandchildren’s telomere length. For each year the grandfathers had delayed reproducing, the grandchildren ended up with telomeres that were the equivalent of one year younger. That is, the telomeres were longer by the same amount that they would have ordinarily shortened in one year.
Obviously, there’s nothing you can do about your own birth circumstances, let alone those of your father’s. But should you take this information into account going forward? Should you delay or encourage your male offspring to delay having children as long as possible? I’ll just point out that longevity and child-rearing are both more complicated than simply measuring telomeres. In fact, there is some evidence that children born to older fathers have shorter rather than longer life spans. In short, don't rearrange your life plans to suit your telomeres.