The New York Genome Center has put together a 13-million-person family tree. The project has provided several new insights — and has cast some doubt on one theory on longevity.
It is the largest family tree in the world, and the oldest of the ancestors included in it lived some 500 years ago: The project by the New York Genome Center includes 13 million people — more than the population of Belgium — all of them connected in some way.
On average, every family bloodline in the study could be traced back over 11 generations. Most of the people in the family tree come from the USA and Europe. In many cases, migration had occurred.
The study was published in the magazine Science on March 1.
US and Israeli researchers working with Joanna Kaplanis from the New York Genome Center sifted through even more data than this to put together the family tree.
They looked at altogether 86 million profiles deposited at the commercial genealogy website GENi by people from all over the world who have been researching their ancestry. GENi now has more than 110 million people listed in its databases.
The researchers examined dates of birth, marriage and death. In order to arrive at one single ancestor for all the 13 million people, the family tree would have to go back 64 generations further.
Women moved away more often — but not as far
The study revealed several interesting facts. For example, people were not very mobile in the early modern era. Even as late as 1750, most Americans found their spouses within a radius of just 10 kilometers (6.2 miles). And before 1850, most people even married within their own families — on average, a fourth cousin.
People born in 1950 were much more willing to travel to find a suitable partner: on average, 100 kilometers. It was mostly women who changed their location of residence for marriage, but men who were forced to migrate traveled much further.
Longevity — not just in the genes
The researchers also found that genes alone play a fairly small role in whether someone lives to a great age.
They analyzed a selection of 3 million profiles from interrelated people who were born between 1600 and 1910. The family comparisons showed that genes were the main factor in a long life in 16 percent of cases. Previously, the figure was put much higher — up to 30 percent. The researchers deduce that good genes could extend someone's life by five years on average.
"That's not a lot," says the study co-author, Yaniv Erlich. "Previous studies have shown that smoking takes 10 years off of your life. That means that some life choices could matter a lot more than genetics."