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According to a new analysis of an aggregate set of genealogical trees of more than 400 million people, genetics has far less influence on the length of life than the one we thought before.
The study suggests that the heritability of life span is well below previous estimates, which has not allowed us to report on our tendency to select partners with traits similar to ours.
"We can potentially learn a lot about the biology of aging through human genetics, but if the heritability of life span is low, it changes our expectations about the types of things we can learn and the ease with which they will be learned, "said lead author Graham Ruby of Calico Life Sciences – a US research and development company.
"It helps to contextualize the questions that can be posed effectively by scientists studying aging," she added.
Heritability measures the length of life that can be explained by genetic differences, excluding differences in lifestyle, socio-cultural factors and accidents.
While previous estimates of the heritability of human lifespan ranged from about 15 to 30%, in the new study, this percentage was probably not more than 7%, perhaps even lower.
For the study, published in the journal Genetics, the team used online genealogy resources with public genealogical trees generated by subscribers representing six billion ancestors.
Removing redundant entries and those still living, they sewed more than 400 million people, mostly Americans of European descent.
Each was linked to another by a parent-child relationship or by spouse.
They focused on family members born in the 19th and early 20th centuries and noted that the spouses' longevity tended to be correlated, more similar to siblings of the opposite sex.
Comparing different types of in-laws, they found that the brothers-in-law and the cousins had a correlated life, even though they were not blood relatives and shared usually not the same households.
The finding that the sibling's sibling's brother or sister or their spouse's spouse had a life span similar to theirs clearly proved that there was something else at stake, said the researchers.
The answer could be in assortative mating. People tend to choose partners with traits like theirs – in this case, how long do they live, they explain.
Ians
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