From 930,000 to 813,000 years ago, environmental conditions on Earth funneled our human ancestors into a protracted "population bottleneck," per the journal Science.
The entire human population, all on the African continent, got culled from an already mere 100,000 to about 1,280 "breeding individuals,” aka people who could produce offspring.
The most prominent human species during the population bottleneck was Homo erectus, the long-surviving human species that existed from 1.89 million to 110,000 years ago.
The pressure to survive and the environmental conditions of the time might've contributed to speciation (the branch-like divergence of species) and the rise of new human species.
These species included Homo heidelbergensis (the first humans to control fire), Homo neanderthalensis (our closest human cousins), and Earth's current humans — Homo sapiens.
The population bottleneck of 1,280 lasted for 117,000 years. Professor Chris Stringer at the Natural Museum of London told The Guardian, "It’s an extraordinary length of time."
He added, "It's remarkable that we did get through at all. For a population of that size, you just need one bad climate event, an epidemic, a volcanic eruption and you’re gone."
After the bottleneck, the population remained at a stable, but still meager, 21,160 people all the way until Homo sapiens' mass exodus from the African continent 100,000 years ago.