Although long life tends to be managed in the family, genetics has a far less influence on the life span than previously thought, according to a new analysis of an aggregate set of genealogical trees of more than 400 million people.
The study suggests that lifespan inheritance is well below previous estimates, which did not take into account our tendency to select partners with similar traits to ours.
"We could learn a lot about aging biology from human genetics, but if lifelong inheritance is low, we're hardening our expectations about what types of things we can learn and how easy it will be," he said. Chief author Graham Ruby, of Calico Life Sciences – a research and development company based in the United States.
"It helps to contextualise the questions that aging scientists can actually ask for," he added
Heritability measures how much life time can be explained by genetic differences, excluding differences in lifestyle, socio-cultural factors and accidents.
While previous estimates of human inheritance life were between 15% and 30%, in the new study it was probably no more than seven percent, perhaps even lower.
For the study, published in Genetics magazine, the team used online genealogy resources with public genealogical trees generated by subscribers representing six billion ancestors.
By removing the redundant voices and those of people who were still alive, they sewed up the remaining pedigrees along with more than 400 million people, mostly Americans of European descent.
Each of them was connected to another by a parent-child or spouse-spouse relationship.
They focused on relatives born between the nineteenth and early twentieth century and noted that the spouses' life span tended to be related, more similar to that of the opposite-sex brothers.
By comparing different types of acquired relatives, they found that brothers-in-law and first-degree cousins had a correlated lifespan, although they were not blood relatives and generally did not share families.
The discovery that the sister's brother of one of the brothers of the mother or the spouse of the brother of his bride had a life span similar to them made it clear that there was something else at stake, the researchers said .
The answer may be in assorted pairs. People tend to select partners with traits like theirs – in this case, how long they live, they explained.