A new genomic model indicates a significant bottleneck in human ancestor populations between 800,000 and 900,000 years ago, aligning with the era of the last common ancestor of Denisovans, Neanderthals, and modern Homo sapiens. Further archaeological evidence is needed for validation.
Between 800,000 and 900,000 years ago, a significant crash occurred in the population of our human ancestors according to a new study. In the research, Wangjie Hu and colleagues present a compelling genomic model, indicating that a mere 1280 breeding individuals existed during the transition from the early to middle Pleistocene. This population bottleneck endured for about 117,000 years.
At the outset of the bottleneck, the ancestral population experienced a staggering 98.7% decline. The decline correlates with climatic changes characterized by extended glaciations, lowered marine surface temperatures, and likely prolonged droughts across Africa and Eurasia.
Introducing the Coalescence Model
Hu and his team pioneered a coalescence model, a tool designed to explore the divergence between gene lineages and estimate past population sizes. They employed this model to study the genomic sequences from 3,154 individuals across 10 African and 40 non-African populations. Their analysis showed a distinct bottleneck in all African populations. However, the bottleneck’s evidence was subtler in the 40 non-African populations. Hu and his team state that the ancient “bottleneck was directly found in all 10 African populations, but only a weak signal of the existence of such was detected in all 40 non-African populations.”
Relation to Last Common Ancestor
This proposed bottleneck aligns with the time period many experts believe the last common ancestor of Denisovans, Neanderthals, and modern Homo sapiens lived. However, Nick Ashton and Chris Stringer, in a related perspective, argue the need to test the bottleneck theory against tangible archaeological and fossil human evidence.
“If, as seems likely, humans were widespread inside and outside of Africa in the period between about 800-900,000 years BP … whatever caused the inferred bottleneck was limited in its effects on the wider non-sapiens lineage populations, or any effects were short-lived,” the Perspective authors add.
For more on this research, see Humanity’s Near-Extinction Event Revealed.
“Genomic inference of a severe human bottleneck during the Early to Middle Pleistocene transition” by Wangjie Hu, Ziqian Hao, Pengyuan Du, Fabio Di Vincenzo, Giorgio Manzi, Jialong Cui, Yun-Xin Fu, Yi-Hsuan Pan and Haipeng Li, 31 August 2023, Science.
“Did our ancestors nearly die out? Genetic analyses suggest an ancient human population crash 900,000 years ago” by Nick Ashton and Chris Stringer, 31 August 2023, Science.