New research into human evolutionary biology shows that the key differences between modern humans and Neanderthals were brought about by certain genetics switches. These switches controlled the phenotypic expression of certain genes by turning them "on" or "off."
Scientists have long been trying to understand the mechanisms that brought about the differences between Neanderthals and modern humans. After all, the two species happen to share approximately 99.8 percent of their DNA. Due to the almost identical makeup of the two species, researchers attempted to unravel the mystery of how the differences came about.
"Ancient DNA sequencing has recently provided high-coverage archaic human genomes. However, the evolution of epigenetic regulation along the human lineage remains largely unexplored," says the study. "We reconstructed the full DNA methylation maps of the Neanderthal and the Denisovan by harnessing the natural degradation processes of methylated and unmethylated cytosines."
The research team that conducted the study was lead by Hebrew University of Jerusalem geneticist Liram Carmel. To understand the genetics behind the mystery, the team compared DNA extracted from a Neanderthal and a modern human. To further increase the accuracy of their study, the researchers also analyzed DNA from a Denisovan, an extinct human species that was known to live in Eurasia sometime during the Stone Age. The team published its findings in the online journal Science.
The team determined that genetic switches controlled the differences in brain size and development as well as other physiological differences like limb anatomy and facial features. The new findings highlight a further need to understand the epigenome, which refers to the mechanisms that control the genetic switches triggering the expression of certain genes.
"People are fundamentally interested in what makes us human, in what makes us different from Neanderthals," University of Pennsylvania evolution specialist Sarah Tishkoff said. She added further that the discovery was "an amazing technical feat." Tishkoff was not involved in the study.
Aside from physical differences, the team also found that the epigenome affects a broad array of traits including the susceptibility of individuals to certain diseases. Studying the epigenome could also lead to a deeper understanding about the differences between twins in humans. Despite the fact that twins share identical genetic materials, differences are known to exist.
Chris Stringer, a researcher from London's Natural History Museum who was also not involved in the study stated that the new discovery "may help to explain how these ancient humans were able to build stronger bodies, better adapted to the physical rigors of Stone Age life."