A recent study that claims the human species escaped extinction around 900,000 years ago, thanks to just 1,280 individuals, has been seriously questioned by many scientists.
The study sparked a lot of media interest in early September. And for good reason, according to an article published in the journal in late August Science And a team of Chinese and Italian researchers signed off, saying humans may have come very close to extinction due to a disruptive event 900,000 years ago.
>> Read More: A study suggests that 900,000 years ago, humans were on the brink of extinction
Our ancestors would have seen almost 99% of the population disappear due to violent climate cooling.
The team used genetic analysis to determine that the existence of the ancestors of modern humans has been under threat for at least 120,000 years.
“Inconclusive Study”
But many critics, such as Aylwyn Scaley, a human evolutionary genetics researcher at the University of Cambridge, greeted the publication with skepticism. “The almost unanimous response in the genetics community was that this study was not credible,” he asserts.
No one doubts the possibility of a disruption in the evolution of the population in question, say a drastic reduction in human numbers, but it is the accuracy of the model that is in question.
Computer model
Because it is so difficult to extract DNA from rare fossils of human ancestry that are a few hundred thousand years old, scientists use mutations found in the genomes of modern humans and use computer models to predict changes in the past.
A Chinese team used the genomes of 3,150 modern humans to conclude that “about 98.7% of human ancestors disappeared” by 930,000 years ago, according to study co-author Li Haipeng of the Shanghai Institute of Nutrition and Health.
Over 120,000 years, the population plummeted to 1,300 individuals, according to the study. “Our ancestors were close to extinction and had to cooperate to survive,” he adds.
The population was able to reorganize itself with the increase in temperature, perhaps, “fire regulation”, the researcher adds.
Head modeling of a four-year-old Neanderthal child by the Institute of Anthropology, University of Zurich. [Philippe Plailly – AP/Keystone]
Little genetic diversity
Disruption would have led to strong inbreeding, resulting in less genetic diversity in humans than in other closely related species such as chimpanzees.
This may have contributed to the parallel evolution of Neanderthal, Denisovan and modern human species, which are believed to have diverged from a common ancestor around the same time, according to the study.
“High Doubt”
For his part, Stefan Schiffels of the German Max Planck Institute for Evolutionary Anthropology expressed his “serious skepticism” that the researchers had taken into account the statistical uncertainties in the matter.
According to him, it will “never be possible” to use genetic analysis of modern humans to arrive at a figure as accurate as the 1,280 individuals who lived so long ago.
The population geneticist said the data used had been known for years, and methods of estimating past populations had never concluded that they were close to extinction.
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