Introduction
New research suggests that our early human ancestors came perilously close to extinction approximately 900,000 years ago. This revelation is the result of a comprehensive study conducted by scientists at the University of Texas, shedding light on a critical period in human evolution.
The Severe Bottleneck
Scientists have uncovered evidence of a severe population bottleneck during this era, where a mere 1,280 breeding individuals sustained the dwindling population. This event led to the loss of nearly two-thirds of genetic diversity among early humans. While this may sound alarming, the study indicates that it could have inadvertently accelerated our cognitive development through natural selection.
Innovative Research Method
The research team employed an innovative method known as FitCoal (fast infinitesimal time coalescent process) to infer ancient population size. By analyzing genomic sequences from 3,154 modern-day individuals, they accurately determined demographic insights.
Findings and Implications
The findings, published in the journal Science, reveal that early human ancestors endured a prolonged, severe bottleneck, spanning approximately 117,000 years. While this research provides crucial insights into early to middle Pleistocene ancestors, it also raises numerous questions.
Senior author Dr. Yun-Xin Fu, a theoretical population geneticist at the University of Texas, hailed the breakthrough, emphasizing that FitCoal’s ability to detect the ancient severe bottleneck with limited sequences is a significant advancement.
Professor Giorgio Manzi, an anthropologist at Sapienza University of Rome, explained that the gap in the African and Eurasian fossil records aligns with this bottleneck in the Early Stone Age.
Causes of Population Decline
Scientists attribute the decline in the early human ancestral population to primarily climatic factors. Glaciation events during that period led to temperature fluctuations, severe droughts, and the loss of other species that served as potential food sources.
The bottleneck resulted in the loss of an estimated 65.85% of current genetic diversity, posing a substantial threat to modern humanity.
Speciation Event and Chromosome 2
Interestingly, the bottleneck may have contributed to a “speciation event” where two ancestral chromosomes converged to form what is now known as chromosome 2 in modern humans. This revelation potentially identifies the last common ancestor shared by the Denisovans, Neanderthals, and Homo sapiens.
Unanswered Questions and Future Research
The research team now aims to explore the conditions in which this small population of early humans lived, how they survived the catastrophic climate changes, and whether natural selection during the bottleneck accelerated the evolution of the human brain.
It is believed that the mastery of fire and a shift in climate favoring human habitation may have led to a subsequent rapid population increase around 813,000 years ago.
Professor LI Haipeng, a theoretical population geneticist and computational biologist at the Shanghai Institute of Nutrition and Health, emphasized that these findings are just the beginning. Future research will strive to provide a comprehensive understanding of human evolution during the Early to Middle Pleistocene transition period, unraveling the mysteries of our early human ancestry.
Conclusion
The study’s findings shed light on a critical chapter in human evolution when our ancestors teetered on the brink of extinction. This newfound knowledge has the potential to reshape our understanding of early human history and the factors that contributed to the development of modern Homo sapiens.
