According to the new genetic study, no matter how large America was, the American Native Americans who first settled on the continent consisted of a small group of 250 people.
The first group, known as the founding population, migrated from Siberia to North and South America, according to researcher co-authors, Professor Nelson Fagundes of the Department of Genetics of the Federal University of Rio Grande do Sul in Brazil said about 15,000 years ago.
According to Fagundes, the number of people in the constituent population is the key point, since it determines the size of the genetic diversity transmitted to the next generation
Fagundes also said that genetic diversity would determine how effective natural selection would be in removing bad genes.
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Fagundes says, "When there is a very productive selection in crowded populations, harmful algae (gene variations) can spread in a small population and cause genetic susceptibility to some diseases."
Fagundes and his colleagues examined the DNA samples of 10 Native Americans from various regions of North and South America, 10 from different Siberian groups and 15 from China to calculate how many Native Americans were founding the population.
According to Fagundes, researchers from North America did not involve the Native Americans in research because many of them later mixed up with people who emigrated to America, making it more difficult to pinpoint the original founding group
After reaching the individual's DNA, the researchers looked at the genome of each individual, with nine regions, each containing about 10,000 base pairs or letters.
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Fagundes says researchers know that the genetic diversity in the sample (such as the American Native) is directly related to population size. However, thanks to the fact that the genetic differences between the two populations (such as the American Native and the Siberians) would increase over time, researchers linked DNA data to computer simulation models and ran these simulations backwards to reveal the original size of the founding group.
Researchers said simulation models reached a constituent population of 229 to 300 people, and that eventually the founding population was 250 people.
Fagundes said that this number was too small and would have created a "genetic bottleneck," which would mean very little genetic variation in the first major migration wave to America.
Nevertheless, as Fagundes adds, all of the Native Americans' genetic diversity may have regained new genetic mutations eventually, thanks to the long time it took for the founder population to reach America. Moreover, according to Fagundes, some of the North American Native Americans mixed up with recent immigrants to increase genetic diversity.
Just a guess
Fagundes, "We must not forget that the number 250 is only a guess. It is important to keep in mind that it is very difficult – or even impossible – to predict how many real persons respond to this figure of the effect of about 250 individuals. "
Despite this, the estimate for 250 people overlaps with the results of other studies. "This bottleneck probably contains fewer than 1,000 people, and even fewer (between 150 and 170) people are more likely to have disappeared," says Fagundes. "There are also studies that suggest the effect of fewer people, but the data do not support them."
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It is important for researchers to determine how many of these genetic bottlenecks are for two reasons: First, this number helps researchers understand how many genetic determinants are needed to resolve the genetic diversity of the American Native Americans. Second, this number helps to assess how much of the gene variation in the population is harmful or beneficial.
Researcher Michael Crawford, a professor at the Department of Anthropology at the University of Kansas, says genetic data reveals how ancient migration is taking place in America.
Crawford says that after the Native Americans settled in the new place, followed by the increase in population and fertility, some of the population settled in a neighboring region. Crawdord also adds, "This is how they have settled down to Argentina in 15,000 years."
Live Science. May 10, 2018