A new study published in the journal Science has found that the human population bottlenecked to as few as 1,280 breeding individuals about 800,000 years ago. The study, led by researchers at the Sapienza University of Rome, analyzed genomic sequences from 3,154 people alive today, from 10 African and 40 non-African populations.
The skull of Homo heidelbergensis. Scientists speculate that the species could have arisen owing to the tiny population of human ancestor species-Image Source: The Guardian
The researchers found that the bottleneck occurred in all the African populations, but only a weak signal of the event was detected in the 40 non-African populations. This is probably due to the ancestors of those of non-African heritage having in effect undergone a more recent population bottleneck during the out-of-Africa migration, which would be expected to mask the earlier event.
The researchers believe that the bottleneck was caused by an extreme climate event, such as a drought or a volcanic eruption. They also believe that the bottleneck may have triggered the emergence of a new species, Homo heidelbergensis, which some believe is the shared ancestor of modern humans and our cousins, the 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,” said study co-author Giorgio Manzi, an anthropologist at Sapienza University of Rome.
The timing of the bottleneck roughly coincides with when the last shared ancestor with Neanderthals and another ancient human species, the Denisovans, are believed to have roamed the Earth. Scientists now want to look at whether genetic samples from these ancient cousins share evidence of the same bottleneck, which could give new insights into when, where and why the species diverged.
The study’s findings shed new light on the history of human evolution and the challenges that our ancestors faced. They also highlight the importance of genetic diversity, which helps populations to adapt to changing environments.
