Human Ancestry: 20% of Genetic Makeup Traced to Mysterious Ancient Population, Cambridge Study Reveals

A study by University of Cambridge researchers published in *Nature* indicates that 20% of human genetic composition originates from a mysterious ancestral population. The research suggests two ancestral populations diverged approximately 1.5 million years ago before merging in a mixing event around 300,000 years ago. This challenges the previous belief that humans evolved from a single group of ancestors. According to Trevor Cousins, the lead author, "interbreeding and genetic exchange have likely played an important role in the emergence of new species on several occasions in the animal kingdom." The findings are based on genetic data from the 1000 Genomes Project, analyzed using a statistical model to determine the probability of genes originating from a common ancestor without selection events. The analysis revealed a period where two ancestral populations merged in an 80%:20% ratio, leading to the observed change in human genetic makeup. Aylwyn Scally noted a significant bottleneck in one population post-separation, suggesting a reduction to a small size before slow growth over a million years. This population contributed about 80% of modern human genetic material and is believed to be the ancestral population from which Neanderthals and Denisovans diverged.