Back in my April 11, 2018 Taki’s Magazine column “Ghosts of Africa,” I wrote about a draft scientific paper entitled “Recovering signals of ghost archaic admixture in the genomes of present-day Africans,” by Arun Durvasula and Sriram Sankararaman. Today it has finally been officially published in Science.
While introgression from Neanderthals and Denisovans has been documented in modern humans outside Africa, the contribution of archaic hominins to the genetic variation of present-day Africans remains poorly understood. We provide complementary lines of evidence for archaic introgression into four West African populations. Our analyses of site frequency spectra indicate that these populations derive 2 to 19% of their genetic ancestry from an archaic population that diverged before the split of Neanderthals and modern humans. Using a method that can identify segments of archaic ancestry without the need for reference archaic genomes, we built genome-wide maps of archaic ancestry in the Yoruba and the Mende populations. Analyses of these maps reveal segments of archaic ancestry at high frequency in these populations that represent potential targets of adaptive introgression. Our results reveal the substantial contribution of archaic ancestry in shaping the gene pool of present-day West African populations.
A ghost population is one for which we don’t have fossils yet, but for which we can impute its existence from later DNA. While East Africa has been the home to many famous fossils, the more humid parts of Africa are generally short of fossils.
In other news, researchers argue that most modern sub-Saharan Africans do actually have a fraction of one percent of their DNA tracing back to Neanderthals. Previously, it had appeared that sub-Saharans had virtually no Neanderthal DNA.