It has been a long-held belief that genetics play a role in lifespan. Calico researchers set out to understand just how much of a role genes play in influencing how long we live. The results, published in Genetics, show that genetics likely play a much smaller role in how long you live than previously thought.
Principal Investigator Graham Ruby, a computational biologist at Calico, had this and many more questions on his mind when he started a study, together with Ancestry, to determine how much, if any, influence genes have on lifespan. Estimates had been published in scientific literature that heritability — the measure of how much of a trait could be affected by genetics — could be as high as 25-30%.
Graham worked with the largest aggregate set of family trees built by Ancestry, without personal identifiers, that included more than 54 million families and 400 million people. Using statistical modeling and his knowledge as a computational biologist, Graham and the team analyzed the data at a scale and scope that had never been done before. They concluded that heritability of lifespan appears to be much lower than previously reported — as low as seven percent.
The researchers uncovered assortative mating (the mating pattern where individuals are statistically likely to choose a mate with similar identifiable traits) as the key contributor to the correlation of lifespans between spouses, parent-children, siblings, cousins etc. They first uncovered that spouses had a higher correlation of lifespan than siblings, which while unexpected is not completely surprising, because spouses usually share the same household. However, when they dug deeper, they were surprised to find that this high correlation of lifespan remained steady or didn’t drop as much as expected for associations between people that were not blood related or co-located. The relatively high correlation remained for siblings-in-law, first-cousins in law, first cousins-once-removed in law, and other non-blood related associations.
Concluded Graham, “Genes may still play a role in lifespan, but as our research shows, it’s likely a more reduced role than we surmised when we first began the study. This is important as we think about where to direct our research in human genetics and has already sparked many conversations with my colleagues about how these results may impact our current and future research directions.”