Modern humans split into two populations 1.5 million years ago

Researchers from the University of Cambridge have found new insights into human evolution. They discovered that our ancestors experienced a significant separation around 1.5 million years ago, followed by a coming together again just 300,000 years ago. Traditionally, it was thought that human evolution followed a straightforward path. However, this research reveals a more complex family tree. Geneticist Trevor Cousins, who led the study, emphasized the ongoing interest in understanding human origins. The researchers compared human genetics to a branching tree. Each branch in this tree represents a split in populations that could no longer interbreed. Yet, this model does not fully capture the complexities of the relationships within species. Cousins and his team suspected that similar complexities existed in human evolution. They noted that humans had mixed genes with other species, such as Neanderthals and Denisovans. This genetic blending indicates that human ancestry may have involved more interactions than previously recognized. Using advanced statistical models and genetic data, the researchers identified two significant populations in human ancestry. One population experienced a drastic reduction in size but later contributed most of the genetic material found in modern humans. This group also appears to be the source of Neanderthals and Denisovans. Interestingly, while most non-African modern humans have about 2 percent Neanderthal DNA, the second population only contributed a smaller fraction of our genetic makeup. Despite this, some genes linked to brain function from this group may have been crucial in human evolution. The findings suggest that the idea of human evolution as a tidy process is overly simplistic. The research highlights the complexities and interconnectedness of our genetic heritage. The study has been published in the journal Nature Genetics.