Here's when humans nearly went extinct, reveals new study

They explained that the bottleneck lasted around 117,000 years, with only about 1,280 breeding individuals managing to sustain a population.

“The gap in the African and Eurasian fossil records can be explained by this bottleneck in the Early Stone Age as chronologically. It coincides with this proposed time period of significant loss of fossil evidence,” explained senior author Giorgio Manzi, an anthropologist at Sapienza University of Rome, in a press release. 

The decline in the population of our early human ancestors is believed to be mainly due to changes in climate. Glaciation events during this period caused temperature shifts and severe droughts. 

Additionally, the loss of other species, which could have served as food sources for our ancestors, also contributed to this decline.

The implications of this near-extinction event are nothing short of astonishing. It is estimated that a staggering 65.85 percent of the existing genetic diversity within our species could have been obliterated during this tumultuous era. 

This dramatic loss speaks volumes about the perseverance of our early human ancestors.

Intriguingly, this genetic bottleneck carries an unexpected twist; the struggle for survival during this time appears to have played a role in forming modern human chromosomes. 

The mastery of fire

"The novel finding opens a new field in human evolution because it evokes many questions," explained senior author Yi-Hsuan Pan, an evolutionary and functional genomics expert at East China Normal University (ECNU).

"Such as the places where these individuals lived, how they overcame the catastrophic climate changes, and whether natural selection during the bottleneck has accelerated the evolution of the human brain."

They highlighted how the mastery of fire and a shift towards a more hospitable climate around 813,000 years ago might have been crucial factors that allowed the human population to rebound.

"These findings are just the start," concluded LI Haipeng, a theoretical population geneticist and computational biologist at the Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences (SINH-CAS).

"Future goals with this knowledge aim to paint a more complete picture of human evolution during this Early to Middle Pleistocene transition period, which will, in turn, continue to unravel the mystery that is early human ancestry and evolution."

The complete study was published in Science on August 31 and can be found here.

Study abstract:

Population size history is essential for studying human evolution. However, ancient population size history during the Pleistocene is notoriously difficult to unravel. In this study, we developed a fast infinitesimal time coalescent process (FitCoal) to circumvent this difficulty and calculated the composite likelihood for present-day human genomic sequences of 3154 individuals. Results showed that human ancestors went through a severe population bottleneck with about 1280 breeding individuals between around 930,000 and 813,000 years ago. The bottleneck lasted for about 117,000 years and brought human ancestors close to extinction. This bottleneck is congruent with a substantial chronological gap in the available African and Eurasian fossil record. Our results provide new insights into our ancestry and suggest a coincident speciation event.