About a million years ago, some cataclysmic event nearly wiped out humanity’s ancestors.
Genetic data from 3,154 modern humans suggests that the population dwindled from around 100,000 to just 1,280 breeding individuals around 900,000 years ago. This resulted in a 98.7 percent population decline that lasted 117,000 years and may have brought humanity to extinction.
Here we are today, and plenty of others, proof that it isn’t. But the results of a team led by geneticists Haipeng Li of the Chinese Academy of Sciences and Yi-Hsuan Pan of East China Normal University in China may explain an interesting gap in the human fossil record in the Pleistocene.
“The gap in the African and Eurasian fossil record can be explained chronologically by this disruption of the Early Stone Age.” Anthropologist Giorgio Manzi says Sapienza University of Rome, Italy. “This is consistent with this proposed period of significant loss of fossil evidence.”
Demographic disturbances, a significant reduction in the number of a group is known, not uncommon. When a species is wiped out by an event such as war, famine, or climate crisis, the decline in genetic diversity can be traced through the descendants of the survivors. We know that there was a human population disturbance in the Northern Hemisphere as recently as 7,000 years ago.
However, teasing out a meaningful signal at the time you want to see it is more challenging.
For this latest analysis, the research team developed a new method called the Fast Infinitive Time Correlation Process (FITCOL) to avoid the accumulation of numerical errors typically associated with trying to unravel past events.
They used FitCoal to analyze genetic data from 3,154 people around the world, from 10 African and 40 non-African populations, to see how genetic inheritance has changed over time. Their results showed a significant population disruption around 930,000 to 813,000 years ago, which saw a loss of up to 65.85 percent of the current genetic diversity.
As for what caused the disruption, we’re not 100 percent sure what all the contributing factors might have been, but there was a major event going on at the time – Mid-Pleistocene transitionEarth’s glacial cycles changed dramatically during this time.
Climatic turbulence may have created inhospitable conditions for human populations scrambling to survive at the time, resulting in famine and conflict further reducing the population.
“The novel discovery opens up a new field in human evolution because it raises many questions.” Pan says“These include where these individuals lived, how they coped with catastrophic climate changes, and whether natural selection accelerated the evolution of the human brain during the bottleneck.”
The disruption seems to have contributed to another interesting aspect of the human genome: the fusion of two chromosomes Chromosome 2.
“These findings are just the beginning.” Li says. “Future goals with this knowledge are aimed at painting a more complete picture of human evolution during this early to middle Pleistocene transition period, which will continue to unravel the mystery of early human origins and evolution.”
Published in the thesis Science.