Previous studies have found that women who have babies naturally in their 40s or 50s tend to live significantly longer than other women. At first it seemed that epigenetic factors were at work here. The theory was that something changes in the DNA of women who give birth late in life leading them to live longer. However, a new study reported today indicates that brothers of women who gave birth late in life also lived longer, but their brothers’ wives did not. “Brothers who had at least three sisters, including at least one sister who gave birth at age 45 or later, were 20 percent to 22 percent less likely to die during any year after age 50 than brothers who had no “late fertile” sisters.(ref)” Moreover,the wives of the brothers lived normal life spans. This suggests that familial genes were a major factor enabling women both to give birth later in life and to live longer as their brothers did, suggesting that the same genes prolong both lifespan and female fertility.
The study is based on examination of birth and death data from two disparate historical databases, a genealogical records database at the University of Utah comprising records of 1.6 million Utah Mormons, and a database at the University of Montreal’s Program on Demographic History Research, which has records on 400,000 people who lived in Quebec between 1608 and 1850, mainly Catholics. The strong religious influences in both populations encouraged large families, and led to some women giving birth in their 40s and 50s. Modern birth control was rarely practiced.
The study’s main author, demographer Ken R. Smith, a professor of family and consumer studies at the University of Utah. Said “If women in your family give birth at older ages, you may well have a chance of living longer than you would otherwise.” “If you have a female relative who had children after age 45, then there appears to be some genetic benefit in your family that will enhance your longevity”. Further, “The new thing here is what most evolutionary biologists long have argued: that survival and reproduction are intrinsically linked to one another. So the novel finding in this paper is discovering this link in humans before modern contraception.(ref)”