Humans Faced Extinction: Only 1,300 Were Left 120,000 Years Ago

New research points to a possibility that humans came close to dying out in the last one million years.

The idea of a “population bottleneck” could help resolve some big questions about how we evolved, but there are still doubts about the study’s conclusive answers, according to the Natural History Museum.

A recent study suggests that nearly ninety-nine percent of our ancient human relatives might have gone extinct about 930,000 years ago.

Humans faced extinction

Researchers analyzed DNA from modern humans to propose that our species experienced a significant population bottleneck.

This bottleneck event involved a drastic reduction in the size of the human population, with estimates suggesting that as few as 1,300 individuals survived this challenging period, which lasted for about 120,000 years.

Though the precise reasons for this near-extinction event are not entirely clear, scientists believe that one major factor was the dramatic shift in Africa’s climate, which became colder and drier during this time.

Migration of Homo sapiens.
Out of Africa theory . pic.twitter.com/IYAi1l4crs

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Dr Yi-Hsuan Pan, who co-authored the research, says, “The novel finding opens a new field in human evolution by raising many new questions.”

Among these questions are those pertaining to the habitat of these individuals, how they overcame catastrophic climate change, and if natural selection during the bottleneck affected their evolution. “All this remains to be answered,” says Pan.

Although many scientists have embraced this research, some still have reservations about the extent of the population bottleneck.

Professor Chris Stringer, a human evolution expert from the Natural History Museum who assessed the paper, expressed his viewpoint, stating that while examining the period of the bottleneck, we have evidence from various locations that suggest humans were still present.

This could imply that the bottleneck may not have been as severe as initially believed. Alternatively, it’s possible that its effects were concentrated in specific regions of the human population, Stringer further explained.

Analysis of genomes from 3,200 people to discover bottleneck

The population bottleneck discovered in this study occurred hundreds of thousands of years before the well-known ‘Out of Africa’ migration event. Researchers used a method they developed called FitCoal to identify it.

FitCoal examined the genetic material of nearly 3,200 individuals from various populations, both within and outside Africa.

Although the mathematical aspects of FitCoal are complex, its foundation is a straightforward concept. It looks at our DNA and the genes it carries, tracing their inheritance through hundreds of thousands of years of ancestry, as explained by the Natural History Museum.

Bottleneck is inferred by a new method (FitCoal), based on the SFS. The authors compare to previous methods, which all don’t find this bottleneck. Why? The paper gives no detailed explanation; a thorough comparison with at least another SFS-based method would be nice. 3/ pic.twitter.com/hXelidpGtf

— Regev Schweiger (@RegevSchweiger) August 31, 2023

When scientists trace these genes backward in time, they eventually blend into older versions that they originally developed from, eventually uniting into a shared ancestor.

This progression is influenced by population sizes, and it helps researchers gauge how these have fluctuated over time.

The researchers’ calculations suggest that there were approximately 1,280 individuals who made up the effective population size between 930,000 and 813,000 years ago. This finding strongly indicates the existence of a population bottleneck.