The small group of hunter-gatherers now living in Southern Africa and known as the Khoisan speak in 'click' languages, and have maintained the greatest genetic diversity known among human populations.
New genetic research has revealed that a small group of hunter-gatherers now living in Southern Africa once was so large that it comprised the majority of living humans.
Only during the last 22,000 years have the other African ethnicities, including the ones giving rise to Europeans and Asians, have become the bigger populations, researchers say.
However, their fall has been quick - the Khoisan (who sometimes call themselves Bushmen) now number about 100,000 individuals, while the rest of humanity numbers 7 billion.
The Khoisan (who sometimes call themselves Bushmen) now number about 100,000 individuals, while the rest of humanity numbers 7 billion. however, they once comprised the biggest group on Earth, new analysis has found.
The paper's first author Hie Lim Kim, formerly at Penn State and now at Nanyang Technological University, said 'It is fascinating to unravel the population history of humankind over the last 150,000 years.'
By conducting extensive computational analyses, the team demonstrated that two of the sequenced individuals showed no signs of having inherited any genetic material from members of other ethnic groups.
Interestingly, these individuals are the oldest members of the Ju/'hoansi tribe, which still live in protected areas of Northwest Namibia.
'This and previous studies show that the Khoisan peoples and the rest of modern humanity shared their most recent common ancestor approximately 150,000 years ago, so it was entirely unexpected to find that this group apparently did not intermarry with non-Khoisan neighbors for many thousand years,' said Webb Miller, professor of Bioinformatics at Penn State and a member of the research team.
'The current Khoisan culture and tradition, where marriage occurs either among Khoisan groups or results in female members leaving their tribes after marrying non-Khoisan men, appears to be long-standing.'
The Khoisan tribes, found in southern Africa, lived in near-isolation from the rest of humanity for thousands of years. The distribution of the three language families spoken by Khoisan people is shown on this map in green
The cultural and genetic persistence of the Ju/'hoansi tribe is intriguing, the researchers say, because genetic and genomic analysis of ancient hominid lineages such as the Neanderthals, as well as non-African humans, have shown that intermarrying does occur frequently in these groups and is traceable over the entire time span of 150,000 history during which anatomically modern humans have lived.
'We also observed gene flow for some of the other Khoisan groups, as defined by their largely varying language, but a key finding of this study is that, even today, individuals without genes from other communities can be identified within the Ju/'hoansi population and possibly others,' Schuster said.
'Having identified non-admixed Khoisan individuals, we could compare the effective population size of the Khoisan with that of other humans over more than 100,000 years,' said research-team memberAakrosh Ratan, an assistant professor at the University of Virginia.
'In a twist of fate, the major ethnic groups today in Africa, Asia, and Europe increased in size only after overcoming a population decline about 20,000 years ago.'
