A recent study published in the Sciences Advances journal in mid-February found traces of genes from a “ghost” lineage in the DNA of a sample of West Africans. Half a million years ago, this “ghost” lineage, a population of ancient humans, lived in West Africa, and the species seems to have diverged from modern humans between 360,000 to one million years ago. This new discovery reveals that their genes may make up two to 19 percent of West Africans’ genetic ancestry today.
Although the modern-day human lineage is the only surviving one, traces of other lineages can be found in some people. Previous lineages found in Eurasian populations, including Neanderthal genes, support how genetic differences exist between human populations. The discovery of this “ghost” lineage further supports the idea of more genetic variations among modern-day humans.
Four West African groups have been revealed to have genes from this ghost lineage in their DNA. These groups include Yoruba, Esaan, Cambians and Mende. The Yoruba and Mende contained numerous genetic variations of the ghost lineage, including genes for tumor suppression, male reproduction and hormone regulation, which is uncommon compared to the major genomes. To scientists, this suggests evolution due to environmental conditions. Sriram Sankararaman, a computational biologist at UCLA and an author of the published study, told NPR that researchers used a statistical model to flag parts of this ancient DNA. This technique gathers DNA from individuals and takes out certain chunks of it that unlikely to have not come from a modern human genome in the process.
Richard Montgomery junior Angela Orantes said, “I find it really interesting that scientists have found this incredible information. It’s important because it shows us where we could have come from, as people and evolved into something much greater, and even to serve a greater purpose in our lives.”
The ghost species is speculated to be the late H. erectus, H. heidelbergensis or a similar relative. With new genomic studies, scientists also have strong evidence to suggest that inbreeding between different human ancestors was common. Potential inbreeding was reflected by how there were only traces of this ‘ghost’ DNA, making it harder for scientists to extract the full genome.
It is estimated that this interbreeding occurred sometime in the past 124,000 years. In a statement with Science Advances, geneticist Alan Rogers and his team concluded that Neandersovans (Neanderthals and Denisovans) interbred with a ‘super-archis’ group.
There is also another theory that the DNA of the West Africans bearing the ancient genomes is likely a combination of an archaic population (unrelated to the Neanderthals) and a Neanderthal related ancestry.
Article by Sarasi Gunasekara of Richard Montgomery High School
Photo Courtesy of Creative Commons