On at least one side of my family, everyone’s a banger for almost a century. My grandmother and great-great grandmother lived well into their 90s; my grandmother into her 80s. Naturally, I’ve internalized their longevity as a superior family trait — rationally or not, I believe I’ll live a long life, too, because it’s in my DNA. Right? Bad news: New research has found that longevity is far less inherited than we originally thought.
The new study, from Calico Life Sciences and Ancestry, looked at the longevity of 400 million dead people and their relatives using Ancestry.com records. They went back to the early 19th and 20th centuries, and employed statistical models to compute “heritability estimates” for siblings, first cousins and spouses. Previous research found similar correlations there. But it was the correlation between in-laws, including the remote ones, that sparked the finding. As Science Daily explains it:
The first hint that something more than either genetics or shared environment might be at work was the finding that siblings-in-law and first-cousins-in-law had correlated life spans — despite not being blood relatives and not generally sharing households.
The size of their dataset allowed the team to zoom in on longevity correlations for other more remote relationship types, including aunts and uncles-in-law, first cousins-once-removed-in-law and different configurations of co-siblings-in-law. The finding that a person’s sibling’s spouse’s sibling or their spouse’s sibling’s spouse had a similar life span to their own made it clear that something else was at play.
The something else is assortative mating. We select mates who are like us in a number of ways, and one of the ways we select them, unconsciously, it seems, is based on longevity. Or perhaps not unconsciously, but rather, off of other clues that also correlate with a longer life, such as wealth or education. What’s more, we also pick people with lifestyles similar to ours, which also potentially increases our longevity.
So it’s not that longevity doesn’t run in families. It does. It’s just that it’s not because it’s inherited; it’s because we pick people who are likely to live as long as we do, and by a combination of similarities and similar lifestyles, long-living folks beget long-living folks because we keep picking long-living folks like our own. “It’s rare for a teetotaler to marry a party girl or an ultra-marathoner to marry a couch potato,” senior study author Catherine Ball said of the research.
Previously, science believed that genetics were 15 to 30 percent responsible for how long we kick it on this planet, but this research concludes that genetics are responsible for a mere 7 percent at best.
Of course, this doesn’t mean that genetics won’t influence how long you live — as the researchers note, we do inherit some diseases like cancer. And we do have aging genes that influence how quickly our bodies wear. It just means that we can’t confidently roll through life not sweating how we live just because our parents or grandparents stuck around for a long time. It also means that hoping for genetic tweaks to extend our lifespans might be less likely given that we have more control over our fate than previously thought.
Still, what we can do is hedge against early death by making choices about not just what we eat and whether we smoke and exercise, but also who we shack up with, to roll the dice in our favor.