Dutch family archives hold marriage records going back to 1600. From these records, as from an old account book, you can pull out two columns: how many children a person had and how many years they lived. Scientists argued for a long time over whether these columns are connected. Some believed that if a person has many children, they spend their strength on them and live shorter. Others were doubtful.
A new study tested this idea on nearly three hundred thousand Dutch people born between 1850 and 1915. The researchers compared relatives to figure out what depends on genes and what depends on living conditions. It turned out that the genes responsible for the number of children are almost unrelated to the genes responsible for longevity.
Yet another link did turn up: the age at first childbirth. People whose first children arrived later lived longer, and this was written into their genes. It seems the point is not that early childbirth drains the body, but that the same genes govern both the pace of life and its length. So the old family books are saying: it is not the number of children but the age at which a person first became a parent that points to how fast their inner clock is ticking.
In the studied population, the heritability of number of children in men was 2.5 times higher than in women, which may reflect a greater influence of a man's hereditary qualities (e.g., resources or social status) on his reproductive success.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.