Geneticists analyzed the DNA of more than 100 members of the Raute ethnic group, the last hunter-gatherers of the Himalayas. The researchers found that, as recently as 50 generations ago, the effective population size of their ancestors was stable at approximately 2,500 individuals. However, a sharp decline followed, approximately 1,500–1,100 years ago, reducing this number by approximately 25 times. This was reported in the journal Scientific Reports.
In the northwest of modern-day Nepal, in the Karnali region, live the last remaining hunter-gatherers of the Himalayas—the Raute ethnic group. The nomadic Raute are a short, dark-skinned people numbering approximately 140. They gather wild plants and hunt primarily small monkeys, regularly migrating from place to place in search of food. They also trade their handicrafts (such as large wooden vessels or boxes) with neighbors for rice, iron, and other items. In recent years, the Raute have been willing to accept assistance, but according to eyewitnesses, they often spend the money they receive or earn on alcohol.
Historical information about the origins of the Raute is virtually nonexistent. To shed some light, Inez Derkx of the University of Zurich, along with colleagues from Spain, Nepal, the Czech Republic, and Switzerland, sequenced the DNA of 120 members of the Raute ethnic group and 47 people living in rural areas of the same region. However, seven Raute DNA samples and three other individuals failed quality control and were excluded from further analysis. Furthermore, the scientists encountered a problem: due to strict endogamy, only two Raute individuals were not closely related, which is important for population studies. Relaxing the standard selection criteria allowed the sample to be expanded to ten individuals for some analyses.
To determine how the effective population size of this population has changed over time, the scientists used the GONE program, which calculates this metric over the past 100 generations. The researchers found that for a long time—until approximately 50 generations ago—the effective population size of the Raute ancestors remained stable, reaching approximately 2,500 individuals. However, over the course of just ten generations, there was a very sharp decline—approximately 25-fold. Considering a generation length of 29 years, this sharp drop occurred approximately 1,500–1,100 years ago. After the sharp decline, the effective population size of the Raute ancestors remained low but relatively stable.
Furthermore, scientists have narrowed down the origins of the Raute ancestors. They found no significant evidence that these people were descendants of isolated local hunter-gatherers who inhabited the region before the arrival of farmers and pastoralists. Instead, they are genetically similar to their neighbors, not only to those populations that were hunter-gatherers in the relatively recent past (150–300 years ago)—the Tharu and Kusunda—but also to those who have been engaged in agriculture for the past several thousand years.
It's conceivable that the Raute ancestors abandoned their food-producing lifestyle and returned to hunting and gathering after arriving in the Himalayas. However, the authors of the article consider this scenario unlikely, leaning toward the idea that the Raute gene pool likely formed as a result of a long process of interbreeding between farmers who arrived in the region and local hunter-gatherers, resulting in the erosion of any noticeable traces of the latter.
N+1 previously reported on how geneticists analyzed the DNA of the indigenous people of Papua New Guinea. This analysis revealed that the lineages of European Cro-Magnons and indigenous East Asians diverged from the ancestors of the Papuans approximately 51,200–46,200 years ago.
