Nearly a million years ago, a devastating event nearly wiped out the ancestors of humanity.
Genomic data from 3,154 modern humans indicates a population decline from about 100,000 to only 1,280 individuals breeding about 900,000 years ago. That’s a staggering 98.7% population decline that lasted for 117,000 years and could have led to the extinction of humanity.
The fact that we are here today, in such a large number, is evidence that this was not the case. But the findings, according to a team led by geneticists Haiping Li of the Chinese Academy of Sciences and Yi Hsuan-Pan of East China Normal University in China, would explain a strange gap in the Pleistocene human fossil record.
“The gap in the African and Eurasian fossil records can be explained by this bottleneck in the early Stone Age in historical terms.” says anthropologist Giorgio Manzi Sapienza University of Rome in Italy. “It coincides with this proposed time period of significant loss of fossil evidence.”
Population bottlenecksAs is known, significant reductions in group numbers are not uncommon. When a species is destroyed by an event such as war, famine, or climate crisis, the resulting decline in genetic diversity can be traced back through the offspring of the survivors. This way we know that there was also a human population bottleneck in the northern hemisphere more recently, about 7,000 years ago.
However, the more you want to go back in time, the harder it becomes to get a meaningful signal.
For this latest analysis, the research team developed a new method called a fast micro-time fusion process (FitCoal) to circumvent the backlog of numerical errors typically associated with trying to unravel these past events.
They used FitCoal to analyze the genomic data of 3,154 people from around the world, from 10 African and 40 non-African populations, to look at how gene strains varied over time. Their results showed a major population bottleneck from about 930,000 to 813,000 years ago, which saw the current genetic diversity lose up to 65.85 percent.
In terms of the causes of the bottleneck, we won’t be 100% sure of the contributing factors, but there was one major event that was happening at the time that could have played a role – Mid transitional Pleistoceneduring which the Earth’s glaciation cycles changed dramatically.
It is possible that climatic disturbances produced conditions that were not favorable to the human groups that were seeking to survive at the time, leading to famine and conflict that further reduced population numbers.
“The new discovery opens up a new field in human evolution because it raises many questions.” Pan says“such as where these individuals lived, how they overcame catastrophic climatic changes, and whether natural selection through a bottleneck accelerated the evolution of the human brain.”
The bottleneck appears to have contributed to another interesting feature of the human genome: the fusion of two chromosomes to form chromosome 2.
Humans have 23 pairs of chromosomes; Everything else Humans Alive today – which consists of great apes – have 24. The formation of chromosome 2 appears to have been a complex process. Speciation event Which encouraged humans on a different evolutionary path.
“These results are just the beginning.” tell me. “The future goals of this knowledge are to paint a more complete picture of human evolution during this transitional period from the Early Pleistocene to the Middle Pleistocene, which in turn will continue to unravel the mystery that represents the origin and evolution of early humans.”
The research has been published in Sciences.
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