November 06, 2018
People always attribute their hopes of living a long life to their grandma that is still alive at 97 years old, or how everyone in their family lived to be at least 95 — it’s genetic they say.
A new study suggests that a longer life might not actually have anything to do with your genes. Per Live Science, a study published in the journal Genetics, set out to understand the biology of aging.
To do this, researchers analyzed data from more than 400 million people using publicly available family trees. Since the study was focused on the lifetime of individuals, the study looked at only those who were born in the 1800s or early 1900s and were deceased.
At first glance, the heritability of life spans of siblings and first cousins appear to be around 20 to 30 percent, similar statistic to what's been found previous studies. But here’s the catch — life spans of spouses also tended to be similar. This could be due to spouses sharing a similar environment, the study said. Because they share a home, it’s likely that they share non-genetic factors like diet and sleep habits, which could influence life span.
Further, another interesting “catch”-like finding of this study was that even siblings-in-law and first-cousins-in-law had similar lifespans. This is interesting because they generally don’t live in the same household, nor are they blood relatives.
So, how could this be? One thought is that this sizable data set allowed researchers to examine the effect of what's called ‘assortative mating’, “the phenomenon in which people tend to select spouses who are similar to themselves,” Live Science reports. “If assortative mating was at play, it would mean that factors that are important for life span tend to be similar among spouses,” Graham Ruby, lead author of the study and a principal investigator at Calico Life Sciences, said in a statement.
Assortative mating was likely the root of our previous misunderstanding about inheriting good "long-life" genes because, when researchers accounted for assortative mating, the heritability of life span dropped seven percent. But there are plenty of other factors that could contribute to life span like wealth or height.
However, these findings don't necessarily mean that there aren't genes for longevity. Rather, this study focused on the heritability of life span at a population level and did not look specifically at people's genomes.
The whole reason we’ve been under the impression that longevity is inherited allllll this time is because previous studies failed to take into account that people tend choose romantic partners with similar traits to their own. Which means that past studies may have overestimated the heritability of life span, the researchers said.