With hundreds of millions of genealogical records, the American company Ancestry.com provides first-rate material for researchers, who can look for patterns of longevity between different generations. In other words, to check if, as we tend to think, really, turning many years runs in the family.
This is what a group of experts led by Graham Ruby of the Calico Life Sciences Company and Catherine Ball of Ancestry.com has done. And their conclusion, as they have published in the GENETICS magazine, is that the level of heritability is much lower than expected: well below 10%. The fact that there are several nonagenarians or centenarians in your family does not genetically predispose you to be a Methuselah, experts say . “We can potentially learn a lot about the biology of aging from human genetics, but these data moderate our expectations,” acknowledges Ruby.
Previously, other scientific works had established a range of between 15% and 30% of heritability in life expectancy. But some of these investigations found the correlation not between blood relatives but between spouses , which indicates that genetic predisposition could be confused with the importance of sharing the same environment or choosing someone with traits similar to ours as a partner.
The volume of family trees collected by Ancestry.com, provided by 54 million subscribers, has allowed the analysis to be refined. From absolute confidentiality, the company provided Calico Life Sciences with the year of birth and death, the place of birth, and the family ties of 500 million individuals , mostly Americans and Europeans. The scientists used a method – the structural equation model – that can only be applied with huge amounts of data, as was the case.
Environmental factors weigh more
At first, they worked with the hypothesis of 15-30% heritability, but found that longevity patterns were often repeated between in-laws , without any blood ties. According to experts, this indicates that what is inherited is not genes, but sociocultural factors –social class, income level… – that influence our living for more or less years.
The curious thing is that the correlation in life expectancy also occurred between more distant in-laws, who did not share a home or, of course, DNA. The explanation, they believe, would be in the aforementioned search factor for a partner with similar traits . Of course, it is impossible to know when that person with whom we decide to live will die, but we do take into account factors such as educational and socioeconomic level or apparently inconsequential physical qualities such as height, empirically related to longevity.
The final verdict is that life expectancy is heritable around 7%, or even less.
Más información: J. Graham Ruby, Kevin M. Wright, Kristin A. Rand, Amir Kermany, Keith Noto, Don Curtis, Neal Varner, Daniel Garrigan, Dmitri Slinkov, Ilya Dorfman, Julie M. Granka, Jake Byrnes, Natalie Myres, and Catherine Ball. “Estimates of the Heritability of Human Longevity Are Substantially Inflated due to Assortative Mating”. GENETICS November 2018. 210(3): 1109-1124. DOI: 10.1534/genetics.118.301613
