[Reading Science] Did Humanity Nearly Go Extinct 900,000 Years Ago?

University of Chinese Academy of Sciences Research Team
Population Bottleneck Discovered 900,000 Years Ago
"98.7% Decrease in Total Population Due to Climate Change... Only 1,280 Survivors"

A surprising study has revealed that the ancestors of modern humans were on the brink of extinction in Africa 900,000 years ago.

A research team from the University of Chinese Academy of Sciences announced on the 31st (local time) in a paper published in the international journal Science that the population of human ancestors living in Africa decreased to about 1,280 individuals around 900,000 years ago and did not recover for approximately 117,000 years thereafter. This means that the population of human ancestors at that time declined by up to 98.7%, suggesting that Homo sapiens, modern humans, might not have emerged and humanity could have gone extinct. Li Haifeng, a population geneticist on the research team, explained in the international journal Nature, "The fossil records found in Africa and Eurasia between about 950,000 and 650,000 years ago are uneven, and the discovery of this population bottleneck may explain the differences in those time periods."

To conduct this research, the team developed new methods to closely examine the lives of ancient human ancestors. They devised a technique to reconstruct ancient population fluctuations by analyzing modern human genetic data. After constructing a complex genetic pedigree, they expanded it in detail to identify significant evolutionary events. Stanley Ambrose, an anthropologist at the University of Illinois, evaluated, "This research method allowed us to focus intensively on the period between 800,000 and 1,000,000 years ago, which was previously little known, in a way that had not been done before."

The period between 800,000 and 1,000,000 years ago marks the transition from the early Pleistocene to the middle Pleistocene. Extreme climate changes caused the glacial cycles to become longer and more intense, leading to prolonged droughts in Africa. Researcher Li said, "Due to these climate changes, ancient human ancestors may have gone extinct, and new human species may have emerged. Ultimately, they likely became the ancestors of modern humans as well as extinct relatives such as Denisovans and Neanderthals."

After this difficult period, it was only around 813,000 years ago that ancient human ancestors began to increase their population again. Hao Zhiquan, a population genetics professor at Shandong First Medical University who participated in the study, said, "It is still unclear how human ancestors survived and how they prospered again," but added, "The discovered 'population bottleneck' had a significant impact on human genetic diversity and likely determined many important traits of modern humans, including brain size." He continued, "It is estimated that more than two-thirds of genetic diversity was lost at that time, indicating it was a very important period in human evolution, and many important research tasks remain."

The scientific community regards the findings as surprising but acknowledges that much work remains. Nick Ashton, an archaeological researcher at the British Museum, said, "It is interesting that the surviving number was very small, which means they likely lived in a very narrow area suitable for communal living to survive. What is even more surprising is that such a small group survived for such a long time, which suggests that the group had a stable environment that minimized stress and provided sufficient resources."

He also pointed out that the validity of the findings must be supported by practical evidence such as fossil excavations and genetic analyses in the future. Professor Ashton said, "The authors believe that the population bottleneck at that time had a global impact. However, the number of archaeological sites outside Africa suggests that this may not be true, and the population bottleneck is more likely to have been limited to Africa."