The Co-Evolving Lineage Hypothesis: Hidden Genetic Ancestry in Human Evolution

Human evolution is often depicted as a branching tree, where populations split and diversified independently during evolution. However, genome-wide data suggest that there may also be a different dimension to this process, involving migration and gene flow. According to the Co-Evolving Lineage Hypothesis, some human populations might have been partially separated but still interacted with each other through gene transfer. As a result, some genomes might have retained traces of genetic diversity coming from populations that differ from the main human lineage. These genetic signals might help identify ghost populations, Neanderthal and Denisovan admixtures, proposed archaic introgression, and other processes. In general, the Co-Evolving Lineage Hypothesis does not postulate the existence of a particular hominin lineage but highlights the possibility that human evolution might be more complex than traditionally thought.