The early ancestors of humans were reduced to 1,300 individuals and came close to extinction, scientists say

• Early human ancestors faced near-extinction between 800,000 and 900,000 years ago, scientists say.
• An extreme climate event might have caused the evolutionary bottleneck.

Early human ancestors came close to becoming extinct between 800,000 and 900,000 years ago, scientists say.

Scientists believe that an evolutionary bottleneck might have been caused by an extreme climate event, which they estimate left just 1,280 breeding individuals of our ancestors for about 117,000 years, The Guardian reported.

"The numbers that emerge from our study correspond to those of species that are currently at risk of extinction," Giorgio Manzi, an anthropologist at Sapienza University of Rome and a senior author of the study, told the paper.

The results were found by conducting a genomics analysis of more than 3,000 living people, per the study published in the journal Science,

Professor Chris Stringer, who was not involved in the research but is the head of human origins at the Natural History Museum in London, told The Guardian: "It's an extraordinary length of time. 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."

The population decline appears to come around a time of long periods of glaciation, meaning sea surface temperatures decreased and a drought might have occurred in Africa and Eurasia, per The Guardian.

Researchers said that this epoch was also relatively empty on the Earth's fossil record in Africa, which is the collection of fossils found in rock and sediment layers that map out the history of life on the planet.

It is possible that the bottleneck was a local phenomenon, as there is not enough evidence to show that there was a global "blank" in the fossil record of early humans, Stringer said.

This bottleneck might have led to the emergence of a new species, Homo heidelbergensis, believed to be a common ancestor of modern humans, Neanderthals, and Denisovans.

"It was lucky [that we survived], but … we know from evolutionary biology that the emergence of a new species can happen in small, isolated populations," Manzi said, per the paper.

This population decline occurred about the same time human ancestors split from Neanderthals and Denisovans.

Scientists are now planning to study whether Neanderthal and Denisovan genes also show this population drop, which could reveal more about when and why these species separated, The Guardian noted.