Human ancestors may have survived a brush with extinction 900,000 years ago

About 1 million years ago, our distant ancestors hunted in small bands and gathered their food with sophisticated stone tools. Then, about 900,000 years ago, something happened: The number of breeding individuals dwindled to only about 1300, according to a new study modeling ancient population sizes. Our ancestors came within a hair’s breadth of extinction, and populations remained that low for the next 100,000 years or more, researchers argue today in Science . The work, which relies on a new statistical method for estimating ancient population sizes, provides insight into a critical time for our lineage and “fills in a few more pieces of the human evolutionary history puzzle,” says Joshua Akey, an evolutionary geneticist at Princeton University who was not involved with the work.” But others urge caution in adopting its conclusions. Compared with other living primates, contemporary humans have startingly low genetic diversity. For decades researchers have suspected this arose because our ancestors went through a population bottleneck. To explore further, a pair of researchers from the Chinese Academy of Sciences (CAS), Yi-Hsuan Pan and Haipeng Li, and their colleagues, scrutinized modern human genomes. Scientists know approximately how long it takes for mutations to pile up in our genes, and by looking at variations in genes across different populations, they can estimate how long ago those groups diverged. Researchers can rewind this molecular...
Source: ScienceNOW - Category: Science Source Type: news