As 250 Siberians became the first Native Americans

The first group of people to reach the American continent was only 250 individuals, a new genetic study reported.

These people emigrated to America from Siberia (present-day Russia) 15,000 years ago, explained Nelson Fagundes of the Federal University of Rio Grande do Sul, Brazil, one of the study's researchers, published in the journal Genetics and Molecular Biology.

According to the scientist, ascertaining the size of the founding groups is very important because it determines the amount of genetic diversity that is transferred to the descendants of the group. This, in turn, can alter the effectiveness with which natural selection eliminates the bad genes.

"Large populations have a very efficient selection, while in small populations, slightly harmful genes can spread, which may increase genetic susceptibility to some diseases," Fagundes told Live Science.

To reveal the size of the founding group of the continent's population, Fagundes and his colleagues studied DNA samples from 10 Native American individuals from Central and South America, 10 people from different Siberian groups and 10 people from China.

Scientists know that genetic variation within a sample is directly related to population size. This, coupled with the fact that genetic divergence between two populations (such as Native Americans and Siberians) increases over time, allowed researchers to connect DNA data in computer simulation models and determine the original size of the founding group, explained the study leader.

According to the models, the original group consisted of 229-300 people, which led to the final estimation of about 250 people. That number was so small that it would create a "genetic bottleneck," meaning that there was little genetic variation in the population, Fagundes explained.

However, it has been so long since the original group arrived in America that the Native Americans as a whole have had time to regain their diversity through new genetic mutations. More than that, some North American natives have formed unions with people from later migrations, which has also contributed to genetic diversity, the study concludes.