Final answer:
Modern non-African humans carry about 1-4% Neanderthal DNA, indicating past interbreeding between species. Neanderthal genes may also affect certain health conditions today. Research also suggests the possible existence of ghost populations contributing to modern human genetics.
Step-by-step explanation:
Modern non-African humans have been found to inherit about 1-4 percent of their DNA from Neanderthals. This discovery was supported by the DNA analysis of fossil remains, indicating that there was interbreeding between early modern humans and Neanderthals. However, no Denisovan ancestry is present in Europe and only 0.1 percent in China. Research also points towards the possibility of other hominins, referred to as 'ghost populations,' contributing to the modern human genome. One such example is the DNA of certain West African populations, which may include 2-19 percent from an unknown archaic hominin. The presence of Neanderthal DNA has implications for our understanding of human evolution, and interestingly, it may also influence certain health conditions in modern humans, such as depression and blood clotting.