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There was a moment in human history when our entire existence may have desperately clung to a thousand or so people. A DNA-based study found that between 800,000 and 900,000 years ago, our ancestors experienced a severe population crash.

This wasn’t humans dealing with a giant meteor like the one that wiped out the dinosaurs. It was a much slower stretch during which humanity teetered on the brink of disappearing completely. This bottleneck in the human gene pool, comprising roughly 1,280 breeding individuals, lasted about 117,000 years.

Human population levels plummet

According to Scientific American, the study analyzed modern human genomes to piece together what the early human population looked like. By constructing a complex family tree of genes from present-day humans, researchers were able to identify important evolutionary events.

During the Early-Middle Pleistocene, a period within the Ice Age, humans faced severe weather and intense glacial cycles. Most human ancestors may have died out, clearing the path for a new human species to take their place.

Focusing on Africa, the study showed that 813,000 years ago, human populations began to recover and grow again. With an estimated two-thirds of genetic diversity potentially lost, traits like brain size appear to have been among the important features that survived. “It represents a key period of time during the evolution of humans,” population geneticist and study co-author Ziqian Hao said. “So there are many important questions to be answered.”

Understanding evolution and ancestry

What we know about evolution reveals a different story than a simple, continuous line of human improvement. Over time, genetic lines disappear—not dramatically all at once. It’s a slow and steady change, generation after generation.

Human existence isn’t inevitable. Species strength or technical advancement doesn’t guarantee the future or explain our past. It’s contingent on narrow, accidental circumstances. A 2021 study showed that human evolution is better seen as a continuous flow of incremental fragments over time. Categorizing people into races and groups oversimplifies human history.

What does the bottleneck study say about us?

The study reveals humanity didn’t simply decline; it nearly collapsed. With over 98% of our genetic diversity erased, entire branches of the human family tree permanently ceased to exist.

It’s quite possible that if even a few more of those genetic lines had ended, human history could have vanished with them. Most branches of life don’t continue. What we witness today reflects biological persistence and countless moments that could have gone another way.

A 2024 study conducted five billion simulations, revealing that as a species’ population shrinks, its risk of extinction rises. Even stable groups can quickly collapse if their numbers suddenly drop low enough.

A 2025 study found that small populations erode genetic diversity. Isolation increases inbreeding and elevates the risk of extinction. Once a lineage shrinks, recovery becomes vastly more challenging over time. Long-term survival is an exception, not the guiding rule.

Humanity likes to think of itself as the result of an incredibly unique progression. Perhaps studies like these suggest that we are actually what remains when everything else disappears. The reason any of us live today comes down to a small group of ancient outlasters: persevering individuals whose genetic lines are the building blocks of every human living today.