How much life expectancy depends on DNA

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

It used to be thought that the secret to longevity was linked to genes. But recent research refutes this theory.

In 2013, Google co-founder Larry Page announced the founding of Calico (short for California Life Company), created to tackle mortality. Since then, this longevity laboratory has been trying to find answers to fundamental biological questions about aging in the hope of one day conquering death. One of the first hired employees is the renowned geneticist Cynthia Kenyon. Twenty years ago, she doubled the lifespan of a laboratory worm by changing one letter in its DNA.

Kenyon soon recruited bioinformatics scientist Graham Ruby. He didn't want to delve into the genetics of worms or study the colony of long-lived naked mole rats. Ruby wanted to first understand how much genes contribute to longevity in general.

Other researchers have asked this question before, but have come up with conflicting results. Much more data was required to achieve clarity. Therefore, Calico turned to the largest genealogical database in the world - the non-profit organization Ancestry, which specializes in consumer genetics.

In 2015, the companies engaged in joint research Estimates of the Heritability of Human Longevity Are Substantially Inflated due to Assortative Mating. They decided to study whether life expectancy is inherited. To do this, Ruby shoveled through many of the family trees stored in Ancestry. With a team of researchers, he analyzed the origins of over 400 million people who have lived in Europe and America since 1800.

Although longevity is usually a familial trait, it turns out that DNA has a much smaller effect on life expectancy than previously thought.

According to Ruby, the heritability of longevity is no more than 7%. Although previous estimates of the effect of genes on life expectancy ranged from 15 to 30%. So what did Ruby find that other scientists have missed? He simply noticed how often amorous homo sapiens challenge the old adage that opposites attract.

It turned out that in every generation, people are much more likely to choose a partner with a life expectancy similar to their own. And this cannot be attributed to mere coincidence. This phenomenon is called assortability, or non-random pairing. It applies not only to longevity, but also to a whole set of genetic and sociocultural characteristics. For example, people usually choose partners with similar economic status and education.

Ruby first thought about the fact that genes are not everything when he turned his attention not to blood relatives, but to relatives by marriage.

Based on the basic law of heredity - everyone receives half of the DNA from one parent and half from the other, which is repeated from generation to generation - the researchers looked at the family ties between two people and their lifespan.

They analyzed parent-child, brother-and-sister pairs, and various combinations with cousins. Nothing unusual was noticed here. The oddities began when Ruby drew attention to his marriage relatives. It seems logical that you should not have the same genetic characteristics with the spouses of brothers and sisters. But it turned out that people who are tied by family ties through the marriage of a close relative have almost the same probability of living as long as their blood relatives. “While no one has ever identified this effect of assortativeness, it is quite consistent with the fabric of human societies,” says Ruby.

These findings do not invalidate previous work to identify individual genes associated with aging and associated diseases, he said. But finding other such genes will be much more difficult in the future. To identify them, researchers will need very large amounts of statistical data. But this is not a problem for Calico, which, in addition to family trees, gained access to anonymized information about the DNA of millions of Ancestry clients.

Now we can conclude that people themselves have more influence on the duration of their lives than their genes.

More important is not DNA, but other factors shared by family members: environment, culture and nutrition, access to education and health care.

Perhaps that's why Ancestry's chief scientist, Catherine Ball, says the company has no plans to focus on longevity in DNA testing products any time soon.

“It seems like the length of a healthy life now depends more on our own choices,” says Ball. According to statistics, it is possible to track at what moments this indicator significantly decreased: during the First World War in men, and then in both sexes in the second half of the 20th century, when smoking became a common habit.

“Don't smoke or fight. Here are two of my tips,”she continues. Well, find time for training.