An anonymous reader quotes a report from The Guardian: Early human ancestors came close to eradication in a severe evolutionary bottleneck between 800,000 and 900,000 years ago, according to scientists. A genomics analysis of more than 3,000 living people suggested that our ancestors’ total population plummeted to about 1,280 breeding individuals for about 117,000 years. Scientists believe that an extreme climate event could have led to the bottleneck that came close to wiping out our ancestral line. “The numbers that emerge from our study correspond to those of species that are currently at risk of extinction,” said Prof Giorgio Manzi, an anthropologist at Sapienza University of Rome and a senior author of the research. However, Manzi and his colleagues believe that the existential pressures of the bottleneck could 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. Homo sapiens are thought to have emerged about 300,000 years ago. “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 Manzi.
Prof Chris Stringer, the head of human origins at the Natural History Museum in London, who was not involved in the research, said: “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 decline appears to coincide with significant changes in global climate that turned glaciations into long-term events, a decrease in sea surface temperatures, and a possible long period of drought in Africa and Eurasia. The team behind the work said the time window also coincides with a relatively empty period on the fossil record. However, Stringer said there was not convincing evidence for a global “blank” in the fossil record of early humans, raising the possibility that whatever caused the bottleneck was a more local phenomenon. “Maybe this bottleneck population was stuck in some area of Africa surrounded by desert,” he said. The findings have been published in the journal Science.
