Although long life tends to run in families, genetics has far less influence on life span than previously thought, according to a new study.
The results of a study into an aggregated set of family trees of more than 400 million people suggest that the heritability of life span is well below past estimates, which failed to account for our tendency to select partners with similar traits to our own.
Heritability is a measure of how much of the variation in a trait – in this case life span – can be explained by genetic differences, as opposed to non-genetic differences such as lifestyle, sociocultural factors, and accidents. Previous estimates of human life span heritability have ranged from around 15 to 30 per cent.
According to the study published Tuesday, longevity is mostly decided by lifestyle, with less than 10% down to DNA.
The researchers also found the life span of spouses to be similar — more so than siblings of opposite gender. A possible explanation: Spouses live in the same household and therefore share important non-genetic factors, such as diet and general lifestyle.
Of course, you can’t easily guess the longevity of a potential mate. “Generally, people get married before either one of them has died,” jokes J. Graham Ruby, lead author of the study and a scientist and principal investigator at Calico. Because you can’t tell someone’s life span in advance, assortative mating in humans must be based on other characteristics.
The upshot? How long you live has less to do with your genes than you might think.
The research, from Calico Life Sciences and Ancestry, was published in GENETICS, a journal of the Genetics Society of America.