In 2013, Google co-founder and CEO Larry Page announced the establishment of a new company, Calico, dedicated to solving the annoying problem of death and developing life-extending technology. Since then, the company has recruited researchers to try to understand the basic biology of aging in the hope of one day defeating death.
One of the company's first researchers was Cynthia Kenyon, a well-known geneticist and professor at the University of California, San Francisco. In her early research, she discovered that a genetic mutation can double the lifespan of Caenorhabditis elegans.
Shortly after joining Calico, Kenyon recruited a bioinformatics researcher, Graham Ruby. Ruby begins by asking a basic question: How big a role do genes play in determining how long a person lives?
Many scientists have tried to solve this problem before, but the conclusions of different studies are far apart, with values floating between 15% and 30%. To get a more definite answer, a larger database is needed.
Therefore, Calico has partnered with Ancestry, the world's largest online genealogy company. Ancestry has the largest family history database in the world. In 2014, the company said it had 16 billion historical records. In 2015, the two companies signed a research partnership to investigate the genetic mechanisms of human longevity.
They studied the genealogy data of more than 400 million people, many of whom have passed away, and the oldest ones can even be traced back to around 1800. Very large-scale population data show that the impact of genes on a person's lifespan is far less significant than previously thought. They suggested that the proportion of genetic influence on life span may be less than 7%, or even lower.
This study also found an interesting phenomenon: the correlation between life spans between unrelated couples is closer than that between siblings and parents. What's even stranger is that there is also a correlation in lifespan between in-laws. For example, a person's lifespan is also related to his cousin's wife. Researchers believe that this may indicate that the "well-matched" mate selection mechanism plays a role in this. The findings were recently published in the journal Genetics.
How much influence does genetics have on lifespan?
Since 1991, a series of studies from different countries and on different populations have evaluated the proportion of genetic factors affecting life span.
In 1991, researchers studied six families and found that this proportion was between 16% and 22%; research on European royal families and aristocrats showed that this proportion differed between men and women, with men at about 18% and women at about 18%. It was 20%; in 1996, a study of 2,872 pairs of twins in Denmark showed that the genetic proportion of lifespan was estimated to be 26% for men and 23% for women; a study of Swedish twins suggested that this proportion was 33%. In 2018, a study published in Science collected 86 million publicly available information on a crowdsourcing genealogy website to evaluate the genetic mechanisms of longevity. They found that the proportion of genetic factors in longevity was only 15% at most.
Although these studies have confirmed that genetics does not have an overwhelming influence on lifespan, the latest research shows that past studies still overestimate the impact of genetics on lifespan. Researchers from Calico and Ancestry jointly studied the genealogy data on Ancestry, covering more than 400 million people in 54.43 million families. Their birth year, birthplace, lifespan, family relationships and other information were included in the analysis. Different from previous studies, this very large-scale sample data includes not only blood relatives, but also non-blood relatives, or even distant relatives by marriage. The size and uniqueness of the sample gave the researchers an unprecedented look at genetic influences on lifespan, and they found that genetics accounted for no more than 7% of the impact.
Couple longevity correlation
Compared with sisters or brothers, the life span between husband and wife is more correlated, which proves that genetics is not the dominant factor affecting life span. Couples share fewer DNA mutations, suggesting they share certain non-genetic factors that strongly influence lifespan.
The correlation between life spans between couples is greater (higher than the correlation between blood-related opposite-sex siblings)
Researchers pointed out that people are not random when choosing their spouses, they will actively choose those who are more similar to themselves. Similar people, researchers call this situation assortative mating. In other words, people are more likely to choose "well-matched" people to marry. For example, well-educated people are more likely to choose a spouse with a good education background, and people with higher incomes tend to choose spouses from the same income bracket... Previous research has shown that wealth, education, and access to good health care services, These are all associated with healthier living and longer lifespan.
"This means that spouses are very similar to each other in many aspects. In other words, people tend to choose partners who have the same characteristics as themselves," Ruby said. "In terms of longevity, the same is true."
In addition, Couples often share similar living circumstances, such as freedom from disease outbreaks, access to clean water, eating healthy foods, and not smoking.
The more interesting thing happened after the researchers expanded the study object. They examined the brothers of a person's brother's spouse, or the spouse of a person's spouse's brother...
According to the researchers, when they studied these distant The correlation with lifespan did not drop significantly when related to relatives. "If genes determine lifespan, the correlation between them should drop a lot," Ruby said. They gave two explanations: first, the factor of "well-matched" has a great impact on life span; second, income plays a certain role in increasing life span. If a person with a high income combines with another person with a high income, Then the lifespan of husband and wife will be highly correlated, and there will also be a connection between in-laws. Catherine Ball, chief scientific officer of
Ancestry and one of the authors of the paper, said: "Compared with unrelated strangers, a person's lifespan has a higher similarity with in-laws." In addition, by choosing to marry and have children with people who are like themselves, They pass on the factors that affect life span to their children twice as much, but not through genetic means - the parents' lifestyle and attitude towards life will be passed on to their children, thus affecting their children's life span.
"The authors of these papers are very honest. The company they work for is dedicated to understanding longevity genes, but their research this time declares that the heritability of longevity is very low." Yaniv Erlich, chief scientist of MyHeritage, commented in an interview with the media.
"Although the length of lifespan will be affected by certain genetic factors, our research shows that there are many other forces in life that play a significant role." Ball said.
Eat a healthy diet, exercise regularly, and maintain good living habits with your loved ones, instead of relying on the longevity genes of your elders. This is the current advice of researchers to people.
