Questioning A Study Stating That The Human Race Almost Became Extinct 900,000 Years Ago
A number of scientists have questioned the validity of the findings of a recent study that the human race was on the verge of extinction about 900,000 years ago, but it avoided it thanks to only 1,280 individuals .
The study, which was published at the end of August in the journal Science and prepared by a Chinese team, was based on a genetic analysis model through which it concluded that the existence of modern human ancestors was threatened for at least 120,000 years .
But this publication was met with skepticism from scientists who criticized it, including a researcher in human evolutionary genetics at the University of Cambridge, Aylwin Scully, who noted that “an almost unanimous position has emerged among geneticists that this study is not convincing.”
No one doubted the possibility that there had been a severe decline in the number of humans at some point in their development, or what is known as the “population bottleneck.”
But critical scholars considered that the model used lacked the accuracy that the study's authors assumed it had, given the time scale studied and similar methods that had previously led to different results .
Since it is very difficult to extract DNA from rare human fossils dating back hundreds of thousands of years, scientists use mutations in the modern human genome to infer from them, using computer models, the changes that occurred in the past .
Climate cooling
The Chinese team used the genomes of 3,150 modern humans, and concluded from them that “about 98.7 percent of human ancestors became extinct” at the beginning of the “population bottleneck” (930,000 years ago), according to Haiping Li, from the Shanghai Institute of Nutrition and Health, one of the participants. In preparing the study .
The population collapsed over 120,000 years, reaching barely 1,300 individuals, according to the study.
He said: “Our ancestors were on the verge of extinction, and they resorted to cooperation in order to survive.”
The researcher suggested that what happened was the result of climate cooling, and continued until 813 thousand years ago, followed by a population boom accompanied by rising temperatures, and perhaps with the mastery of lighting and using fire .
It is believed that the population bottleneck has led to a large degree of inbreeding, which has led to lower genetic diversity in the human species compared to other closely related species, such as chimpanzees .
This would finally explain why very few human fossils dating back to this era have been found.
However, paleontologists refuted this argument, as they pointed to the discovery of fossils in Kenya, Ethiopia, Europe, and China.
However, Lee argued otherwise that the humans who were then living in Eurasia and East Asia were not necessarily the ancestors of modern humanity.
He said, “The small, ancient population group (that is close to extinction) is the ancestor of all modern humans, otherwise we would not carry traces of it in our DNA.”
Very skeptical
Population genetics expert at the German Max Planck Institute for Evolutionary Anthropology, Stefan Schiffels, expressed “strong skepticism” that the researchers took into account statistical uncertainties in this field .
He believed that using genomic analysis of modern humans to arrive at an accurate number, such as 1,280 individuals who lived such a long time ago, “will never be possible.”
Schiffels added that the data used had been known for years, and that methods for estimating previous populations had never concluded that there was an approaching extinction .
Pontus Skogland, from the British Francis Crick Institute, said that “it is difficult to accept the conclusion” of the authors of this study in light of these data.
Source: websites