Today, there are more than 8 billion people on this planet. Our species dominates Earth’s landscapes, and our activities drive large numbers of other species to extinction. If a researcher had looked at the world 800,000 to 900,000 years ago, the picture would have been quite different. Using a new model called the Fast Infinitesimal Time Coalescent Process (FITCOL), East China Normal University’s Dr. Yi-Hsuan Pan and colleagues analyzed the present-day human genome sequences of 3,154 individuals. Their results show that human ancestors experienced severe population disruptions between about 930,000 and 813,000 years ago with about 1,280 breeding individuals; This disruption lasted about 117,000 years and brought human ancestors close to extinction. This decline appears to have coincided with both major climate change and subsequent breeding events.
Huh and many others. It found that the population size of our ancestors decreased from about 100,000 to about 1,000 individuals, lasting about 100,000 years. Image credit: Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences.
Population size history is essential to studying human evolution.
However, the ancient population size history of the Pleistocene is more difficult to unravel.
To avoid this difficulty, Dr Pan and co-authors developed the FitCol model, which looks at divergence between genetic lineages and can be used to estimate past population size.
„Our discovery opens up a new field in human evolution because it raises many questions, such as where these individuals lived, how they coped with catastrophic climate changes, and whether natural selection accelerated the evolution of the human brain during the bottleneck,” said Dr. Pan said.
Using the FitCol model, the authors analyzed present-day human genome sequences of 3,154 individuals from 10 African and 40 non-African populations.
They found that the population size of our ancestors decreased from about 100,000 to about 1,280 individuals, lasting about 117,000 years.
„The gap in the African and Eurasian fossil record can be explained chronologically by this disruption of the Early Stone Age,” said Dr. Giorgio Mansi, an anthropologist at the Sapienza University of Rome.
„This is consistent with this proposed period of significant loss of fossil evidence.”
„The fact that FitCol can detect ancient severe disturbances with just a few sequences represents an advance,” said Dr. Yun-Xin Fu, a theoretical population geneticist at the University of Texas Health Science Center in Houston.
65.85% of current genetic diversity may have been lost due to ancient disruption, and a prolonged period of low numbers of breeding individuals threatens humanity as we know it today.
This disturbance appears to have coincided with glacial events that led to temperature changes, severe droughts, and extinctions of other species that were used for food by ancient humans.
„These findings are just the beginning,” said Dr. Haipeng Li of the Shanghai Institute of Nutrition and Health.
„Future goals with this knowledge are aimed at painting a more complete picture of human evolution during this early to middle Pleistocene transition period, which will continue to unravel the mystery of early human origins and evolution.”
The Results Published in the magazine Science.
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Wangji Hu and many others. Genetic inference of acute human disturbance during the Early to Middle Pleistocene transition. Science, published online August 31, 2023; doi: 10.1126/science.abq7487