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The population of our ancestors may have plummeted to as low as 1300 around 900,000 years ago, possibly as a result of our ancestral species splitting from other early humans.
That is the conclusion of an analysis of the variation in the genomes of living people by Haipeng Li at the Shanghai Institute of Nutrition and Health and his colleagues. However, while not dismissing the idea outright, independent experts say it isn’t supported by other lines of evidence.
Population bottlenecks occur when an existing population is reduced in size, for instance as a result of a catastrophe, or when a small number of individuals leave one population to found a new one. This results in a sudden loss of genetic diversity.
There have been numerous bottlenecks of varying scales as humans evolved and moved around the world. For instance, there was a major bottleneck when a small number of modern humans left Africa around 60,000 years ago, which is why there is still much more genetic diversity among people of African descent than in everyone living in the rest of the world combined. Much more recently, there was a series of bottlenecks as Polynesians settled island after island in the Pacific.
Past bottlenecks can be uncovered by looking for the reductions in genetic diversity they cause, but more ancient bottlenecks are harder to detect than recent ones. Li’s team developed a new method for estimating past changes in population size and applied it to the genomes of more than 3,000 people from around the world.
According to the researchers’ findings, the population of our ancestors fell by 98 percent to around 1280 “breeding individuals” around 930,000 years ago, and the population remained very low until around 815,000 years ago.
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An ancestral population of humans was reduced to very low numbers, according to a genetic analysis The Natural History Museum/Alamy
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