Human-Hominid Interbreeding: A Scientific Cliffhanger
New research on regulatory genes in humans, Neanderthals, and Denisovans adds yet another twist in the human-hominid interbreeding drama.
As I write this article, the final weeks of the TV season are upon us. Many of my favorite shows are concluding their season run with cliffhangers. I can’t wait for September to find out what happens next!
Only a few years ago (spring 2010) researchers surprised the scientific world with data indicating that humans and Neanderthals interbred. Presumably, these encounters left behind a 1 to 4 percent Neanderthal contribution to the human genome. Since that time, other studies have indicated that humans also interbred with the mysterious Denisovans. In fact, human-hominid interbreeding has practically become orthodoxy among the scientific community. Yet, as with all good plot twists, a number of recent studies indicate that it might be premature to conclude that humans and Neanderthals interbred. (Go here and here for more details about some of the challenging studies.)
Now things are really heating up. New work by a team of collaborators from the US adds yet another obstacle to human-hominid interbreeding.1 Their report revolves around a regulatory region in human, Neanderthal, and Denisovan genomes that displays a signature similar to the ones that led researchers to reach the interbreeding conclusion. This team demonstrates, however, that this signature stems from the population substructure of African people groups and a process known as balancing selection.
This result raises the possibility that the same effects produced the other previously observed markers for interbreeding. The team concludes their paper this way:
Future genome-wide scans for balancing selection, in genomic segments that were previously explained by admixture from archaic hominins are warranted. The results of such studies will likely increase the number of known regions where balancing selection is acting and identify ancient variation that was previously attributed to archaic hominin admixture.2
I can’t wait for the next episode in this on going scientific saga. Did humans and Neanderthal interbreed? Stay tuned.
- Omer Gokcumen et al., “Balancing Selection on a Regulatory Region Exhibiting Ancient Variation that Predates Human-Neandertal Divergence,” PLoS Genetics 9 (April 2013): e1003404, doi:10.1371/journal.pgen.1003404.