Scientists say they have pinpointed the moment when humanity almost died out
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A new study reveals that ancient humanity was nearly wiped out around 900,000 years ago when the global population dwindled to around 1,280 breeding individuals. What’s more, the population of early human ancestors remained this small for about 117,000 years.
The analysis, published August 31 in the journal Science, is based on a new computer model developed by a group of scientists based in China, Italy and the United States.
The statistical method used genetic information from 3154 current human genomes.
According to the study, about 98.7% of human ancestors were lost. The researchers believe that the population collapse is associated with a gap in the fossil record, which could lead to the emergence of a new species of hominin that was the common ancestor of modern humans, or Homo sapiens, and Neanderthals.
“The new discovery opens a new field in human evolution because it raises many questions, such as where these individuals lived, how they overcame catastrophic climatic changes, and whether natural selection during a bottleneck accelerated the evolution of the human brain.” Lead researcher Yi Hsuan Pan, an evolutionary and functional genomics scientist at East China Normal University, said in a statement:
The research team suggested that the population bottleneck coincided with drastic changes in climate during what is known as the mid-Pleistocene transition. Glacial periods are becoming longer and more intense, resulting in lower temperatures and extremely dry conditions.
Furthermore, scientists have suggested that fire control, combined with climate shifting to be more suitable for human life, could have contributed to the subsequent rapid population increase some 813,000 years ago.
The researchers pointed out that the oldest evidence of the use of fire to cook food dates back to 780,000 years ago in what is now modern Israel.
While ancient DNA has revolutionized our understanding of past populations, the oldest DNA of the human species dates back to about 400,000 years ago.
A computer model uses the vast amount of information found in the modern human genome about genetic variation over time to infer population size at specific points in the past. The team used the genetic sequences of 10 Africans and 40 non-African groups.
Commenting on the analysis published in the same journal, Nick Ashton, curator of the Paleolithic collections at the British Museum, and Chris Stringer, research leader in human evolution at the Natural History Museum in London, described the study as “provocative”.
The researchers, who were not involved in the study, said it highlighted “the vulnerability of early human populations”.
However, Ashton and Stringer said the fossil record, while scarce, showed that the early human species lived in Africa and beyond from about 813,000 to 930,000 years ago — during the time of the proposed population crash, with fossils from that era being found in what is now known as in China. Kenya, Ethiopia, Italy, Spain and the United Kingdom.
“Whatever the cause of the proposed bottleneck, it may be limited in its effects on human populations outside the Homo sapiens lineage, or that its effects were short-lived,” the researchers said in the commentary.
“The proposed bottleneck needs to be tested against human and archaeological evidence,” they added.
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