Long life has little to do with genetics

Your genetics may have less impact on how long you will live than previously thought, according to research using family trees consisting of more than 400 million individuals.

Researchers from a Google-sponsored company, Calico Life Sciences, partnered with the online genealogy firm Ancestry for this study. They looked at the lifespan of hundreds of millions of Americans, mainly of European descent, and found that the heritability of human lifespan is less than ten percent – much lower than previously estimated. The authors proposed that this new lower estimate was due to the way humans select mates. 

Earlier studies have estimated the genetic component of lifespan to range from 15-30 percent, but Dr Graham Ruby from Calico Life Sciences and lead study author, said this new work showed 'the true heritability of human longevity for that cohort is likely no more than seven percent'. 

The measure of lifespan heritability indicates how much variation is down to genetics, and how much is a result of other factors, such as lifestyle or accidents. Therefore, this work – published in the journal Genetics – implies that the effect of our genes on lifespan is lower than thought.

Dr Catherine Ball, chief scientific officer at Ancestry, said that 'right now a healthy lifespan looks to be more of a function of the choices that we make'. 

By analysing the public family trees available through Ancestry, the team from California were able to investigate the lifespans of millions of people and how this correlated to the lifespans of their relatives. The authors found heritability estimates for siblings to be similar to those in previous work. However, they also found the lifespans of spouses to correlate as much, or even more, than blood relatives. 

First cousin-in-laws or sibling-in-laws who are not genetically related and do not usually live together also had correlated lifespans. 

These results indicated that a phenomenon called 'assortative mating' could be the reason why life span heritability has previously been over-estimated. Assortative mating is the tendency of humans to select partners with similar physical or genetic traits to themselves. The team developed models to quantify and account for assortative mating. When these models were used, the heritability estimates were consistently less than ten percent, but when the researchers did not account for assortative mating, their estimates matched those in the literature.  

This work is important because the size of the dataset allowed remote relationships to be explored, which had not been possible in previous studies. The results also give greater context to genetic studies of human mortality and ageing and could affect the entire field of longevity studies.

'Partnering with Ancestry allowed this new study to gain deeper insights by using a much larger data set than any previous studies of longevity,' said Dr Ball.