A new study published in Science provides fascinating insights into a pivotal period in human evolution when our species teetered on the brink of extinction.

Researchers from China, Italy, and the U.S. utilized a novel genomic analysis technique called Fast Infinitesimal Time Coalescent Process (FitCoal) to examine this crucial population bottleneck.

FitCoal calculates the likelihood of genetic sequences originating from specific population sizes over time. This enables scientists to infer ancient population dynamics from modern genomes. Using this technique, the study reveals that between 800,000 to 900,000 years ago, the human population plummeted to just 1,280 breeding individuals. This severe bottleneck persisted for around 117,000 years, nearly wiping out our ancestral population.

What factors led to this precarious situation that almost doomed humans?

The study suggests a combination of environmental events like glaciation, temperature fluctuations, and severe droughts impacted our ancestors’ food sources and habitats. This sharp reduction in population resulted in a substantial loss of genetic diversity, with over 65% of present-day human genetic variation potentially lost during this bottleneck period.

Remarkably, early humans clung to existence despite the bleak conditions. Their persistence through this evolutionary pinch point paid off, leading to a pivotal speciation event. The population bottleneck spurred the fusion of two ancestral chromosomes into chromosome 2, a defining genetic trait of modern humans. Further analyses of modern genomes using FitCoal will uncover more insights into the pivotal events and pressures that shaped human evolution.