In 1972, a study suggested a genetic bottleneck in human history, indicating a significant reduction in population 35,000-65,000 years ago. By the 1990s, scientists linked this to the eruption of Lake Toba 74,000 years ago, hypothesizing it caused a severe climate change and nearly wiped out humanity, leaving only 3,000-10,000 survivors. However, recent research disputes the Lake Toba theory, suggesting the eruption's impact wasn't as catastrophic.

In late 2023, a new study identified a severe genetic bottleneck between 800,000-900,000 years ago, affecting early human ancestors rather than modern humans. This event drastically reduced the population to about 1,280 individuals, nearly wiping out 98.7% of early humans. Researchers attribute this bottleneck to a major climate shift during the Calabrian stage of the Pleistocene, particularly the Middle Pleistocene Transition, which caused harsher glacial cycles and environmental strains.

Fossil evidence supports this, showing few hominin remains from 950,000-650,000 years ago. The surviving population may have evolved into Homo heidelbergensis, an ancestor of modern humans and Neanderthals. The lack of fire use and other technologies likely prolonged their struggle for survival, but once fire became common, their population rebounded significantly by 830,000 years ago.

Debate continues over the exact cause and timing of this bottleneck, with some suggesting it happened over a million years ago or involved mass migrations out of Africa. Further research is needed to resolve these questions and understand our ancestors' near-extinction.

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