Scientists have long believed that modern humans descended from a single ancestral lineage. However, new research using full genome sequencing has challenged this view and revealed a more intricate history of human evolution.
The study found that modern humans originated from two distinct populations that diverged around 1.5 million years ago and later merged. This genetic reunion occurred roughly 300,000 years ago, resulting in one group contributing 80% of modern human DNA and the other providing 20%.
The findings suggest that human evolution was far more complicated than previously thought. The researchers used a computational tool called cobraa to model how human populations split and later merged, revealing a severe bottleneck in one of the ancestral populations.
This smaller group later contributed most of the genetic material found in modern humans and was also the ancestral population from which Neanderthals and Denisovans evolved. In contrast, the second population carried genes related to brain function and neural processing, which were often located in regions of the genome unrelated to primary gene functions.
The researchers believe that natural selection filtered out less compatible genetic traits over time, ensuring only beneficial genetic changes persisted. This process, known as purifying selection, is thought to have played a crucial role in shaping human evolution.
The study also found evidence of similar ancestral population structures in other species, such as bats, dolphins, chimpanzees, and gorillas. The researchers suggest that interbreeding and genetic exchange likely influenced the development of these species across the animal kingdom.
While the identities of the ancestral human populations remain uncertain, the findings offer new insights into the evolutionary history of our species. Further research is needed to refine the genetic model and account for gradual genetic exchanges rather than abrupt splits and reunions.
Source: https://www.earth.com/news/hidden-chapter-in-human-evolution-revealed-through-genetics