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Long lifetimes tend to occur in families, a phenomenon often attributed to people's genes. But now, a major new study on Ancestry's genealogy website data reveals that genetics may play a less important role in the lifespan than previously thought.
The reason? Previous studies had failed to take into account a quirk of human relationships: people tended to select romantic partners with traits similar to theirs. The results indicate that previous studies may have significantly overestimated the heritability of the lifespan, the researchers said.
The study was published today (November 6) in the journal Genetics. It was funded by Calico Life Sciences, a research and development company owned by Alphabet Inc. (parent company of Google), whose mission is to understand the biology of aging. [7 Ways the Mind and Body Change With Age]
"Matching mating"
In a given population, people will vary in different ways; they will have different heights, the color of the eyes and, yes, the life span.
Heritability is a measure of the extent to which variability in a given trait, such as lifespan, is explained by variability in people's genes, in contrast to environmental factors such as healthy eating or eating. 39; exercise. Previous studies had estimated that the heritability of life span was 30%.
In the new study, researchers analyzed the information of more than 400 million people with the help of publicly available family trees from Ancestry. Since researchers needed to know the lifespan of these people, the study focused only on those born in the 1800s or early 1900s and deceased. (Before sharing this data, Ancestry removed all identifiable information from family trees.)
An initial analysis revealed that, in comparing the life span of brothers and sisters and first cousins, the heritability of life seems to be around 20 to 30%, which is comparable to previous studies.
But the life of the spouses also tended to be similar. This could be due to spouses sharing a similar environment, the study said. Since they live in the same household, they can share many non-genetic factors, ranging from diet to sleep patterns, which can affect the life span.
But then, the researchers noted something curious: they found that even brothers-in-law and cousins had a correlated lifespan, even though they did not usually live in the same household or were related to blood.
But if they do not share a close family history or similar environment, why do distant and unrelated parents also have a linked life? The large amount of data allowed researchers to examine the effect of what is known as assortment matching, a phenomenon in which people tend to choose spouses who are alike. If matching couplings were at stake, it would mean that important factors for life span tend to be similar between spouses, said Graham Ruby, lead author of the study and lead investigator of Calico Life Sciences.
Indeed, the researchers found that this was the case and, when they took into account the assortative mating, the heritability of the life span fell to 7%.
However, the study does not say that people choose a partner based on their life span because that would be impossible, Ruby said. "People usually get married before the death of one or the other," said Ruby jokingly.
But other factors could be at play, including genetic and non-genetic variables. For example, if wealth is tied to the length of life and the rich tend to marry other rich people, this might give the impression that the life span is more hereditary than it is. she really is, the researchers said. Or if size – a trait partially influenced by genetics – is linked to life expectancy and large people tend to marry other large people, it would also confuse heritability analysis. lifetime.
However, the results do not mean that there are no longevity genes. The study focused on the heritability of life span at the population level and did not specifically examine the genome of people. Previous studies have shown a link between certain genes and a long life span.
Originally published on Science live.
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