Researchers report a recent discovery of a population bottleneck in early humans, occurring when ancestral groups briefly exceeded about a thousand individuals across multiple generations, a finding summarized in Science.
The bottleneck effect describes the loss of genetic diversity that happens when a population drops to a small size for a period, making it harder for the group to adapt to changes and survive in the long run.
Scientists led by Yun Xinfu of the Texas Health Science Center applied a fresh association model to estimate past human populations by analyzing more than 3,000 modern genomes, offering new insight into how ancient sizes translated into present-day diversity.
The study indicates that human ancestors endured a population bottleneck roughly between 930 and 813 thousand years ago, with about 1,280 individuals at the peak of this decline. The bottleneck persisted for roughly 117,000 years, pushing ancestral lineages toward the brink of extinction before recovery began.
Researchers note that this bottleneck aligns with a visible mismatch in the fossil record between African and Eurasian specimens, suggesting a period of geographic and evolutionary separation during that era.
This marked decline in population coincided with major climatic shifts during the Pleistocene, commonly known as the Ice Age, and it appears to have influenced subsequent patterns of speciation and geographic dispersion.
Earlier publications in the scientific literature have suggested that about 1.2 million years ago the human population dipped to roughly 18,500 to 26,000 individuals. There is also a theory that the number fell to around 2,000 following the eruption of the Toba supervolcano about 75,000 years ago, a catastrophe that likely disrupted populations across parts of Africa and Asia.
Historically, scientists have also explored theoretical scenarios in other fields, such as how experts model extreme events to understand potential safe strategies in distant, hypothetical nuclear scenarios, underscoring the broad interest in population dynamics and risk assessment.