Ancient Genetic Mixing Seen in Immune System Genes

While it was thought that many of the places in the genome that Neanderthal and Denisovan DNA mixed with modern human's were non-functional, this study shows that this mixing had profound impact on the modern human immune system.  This report looked specifically at HLA genes (coding for HLA proteins).  In European, Asian, and New Guinea populations, more than half the genetic variation in the HLA gene can be attributed to ancient genomic mixing.  The article suggests that this mixing was a way for modern human ancestors to acclimate to new bacteria when moving out of Africa.