Human nearly extinct 900,000 years ago: study
A new inference method decodes the potential extinction of our ancestors.
Our human ancestors almost went extinct about 900,000 years ago due to catastrophic climate changes, a recent study shows.
Modern humans, known as Homo sapiens, emerged in Africa around 300,000 to 200,000 years ago, but genetic research into human evolution is confined largely to the recent 100,000 years. It can't solved by using ancient DNA, because ancient DNA can't survive long in hot climates.
Hence, a team of researchers from China, Italy and the US developed a novel method called FitCoal (fast infinitesimal time coalescent process) to conduct a census of population on our ancestors.
They analyzed genomic sequences from 3,154 present-day humans and found that our ancestors dwindled to just 1,280 breeding individuals about 930,000 years ago, and the population hovered around for 117,000 years.
"Nearly 98.7 percent of our human ancestors were lost," said Li Haipeng from the Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences (SINH-CAS). "An estimated 65.85% of current genetic diversity may have been lost due to this bottleneck in the Early to Middle Pleistocene era."
"The gap in the African fossil records can be explained by this bottleneck in the Early Stone Age as chronological. It coincides with this proposed time period of significant loss of fossil evidence," said Giorgio Manzi at Sapienza University of Rome.
Reasons suggested for this downturn in human ancestral population are mostly climatic. Glaciation events around this time led to changes in temperatures, severe droughts, and loss of other species, potentially used as food sources for ancestral humans.
"The novel finding opens a new field in human evolution because it evokes many questions, such as the places where these individuals lived, how they overcame the catastrophic climate changes, and whether natural selection during the bottleneck has accelerated the evolution of the human brain," said Pan Yi-hsuan from the East China Normal University.
According to Li, it will also shed light on research into human origins, evolution of tumors, brain size change, and even our susceptibility to diabetes.
This research, jointly led by Li and Pan, has been published in Science.
