Human ancestors may have become extinct 900,000 years ago: study
Just as climate change threatens the human race today, an eerily similar global event nearly wiped out our ancestors, reducing the early human population to just 1,280 people for over a hundred thousand years! According to the International Union for Conservation of Nature’s criteria, hominids are classified as “endangered” or “critically endangered.”
For many years, scientists have been trying to map human evolution — hardly a straightforward journey — by selecting one fossil at a time. While we have a fairly good understanding of what happened before modern humans evolved, we certainly have some gaps to fill.
One of the greatest mysteries of human evolution is the inexplicable gap in the African and Eurasian fossil record from 950,000 to 650,000 years ago. It was unlikely that these species simply fell off the face of the Earth and then reappeared out of nowhere. But researchers have found shocking things that could explain this gap in our fossil records.
Scientists from the United States, Italy and China conducted a genomic analysis of 3,154 people today to trace their characteristics back in time and establish the population patterns that most likely gave rise to their current genomes.
This study revealed that the number of human ancestors decreased between 800,000 and 900,000 years ago. Just over 1,000 individuals survived (compared to 27,000 individuals who lived before) during this transition between the early and middle Pleistocene, meaning 98.7% of our ancestral population was lost. Furthermore, the bottleneck lasted for approximately 117,000 years!
During this period of great genetic contraction, an estimated 65.85% of the current genetic diversity of modern humans may have been lost. One interesting finding is that this bottleneck may have contributed to a speciation, where two ancestral chromosomes fused to form what we now know as chromosome 2 in modern Denisovans, Neanderthals, and Homo sapiens.
As for the cause of this perilous death, the study authors believe that a deep cooling event may have been responsible. Around this time in history, glaciation caused extreme temperature fluctuations, severe droughts, and the extinction of animals that the ancestral species likely depended on for food.
However, more research is needed to understand where these ancient populations lived during this difficult period, how they survived the changing climate, and whether natural selection at a time of bottleneck accelerated the evolution of the human brain.
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