It is well-known that people from Europe and Asia have traces of Neanderthals and Denisovans in their DNA. These are markers from where early modern humans interbred with other hominin species, producing children that inherited genes from both.
…Neanderthals and Denisovans bred with modern humans that had already left Africa, the birthplace of modern man. As a result, people in Africa have less genetic input from Denisovans and Neanderthals.
“Results strongly support that an African archaic (ghost) lineage that diverged from modern humans slightly before Neanderthals and Denisovans, perhaps 600,000 years ago, met and interbred with the ancestors of West African populations,” he told Newsweek. “Interestingly, this might have happened even before the split between African and non-African populations, whereby global human groups might carry ancestry from this ghost lineage.
“This work sheds light on the complex patterns of human evolution, where a simple narrative does not conform to the data. The picture will only get more complex, especially when more work is done in Africa, the birthplace of humanity.”