Final answer:
Neanderthals and modern humans split around 370,000 years ago, interbred, and modern non-African humans carry 1 to 4 percent Neanderthal DNA. Neanderthals had adaptations in skin and hair and may have had speech capabilities. Their extinction is potentially due to competition, disease, or climate challenges.
Step-by-step explanation:
Neanderthal DNA provides insights into the complexities of human evolution and our relationship with Neanderthals. The genetic split between modern humans and Neanderthals is estimated to have occurred around 370,000 years ago. Neanderthals are considered a separate species, Homo neanderthalensis, with a distinct lineage from modern humans, although they interbred with Homo sapiens. There is evidence to suggest Neanderthals had the capacity for speech, though perhaps not as developed as modern humans.
Neanderthals likely had adaptations in their skin and hair suited to the colder climates they inhabited, with some evidence implying they had lighter skin and hair than their African ancestors. Today, many people outside of Africa carry around 1 to 4 percent Neanderthal DNA, indicating that interbreeding did occur. Not all humans possess Neanderthal DNA; sub-Saharan African populations have little to no Neanderthal DNA, reflecting the migrations and interbreeding that happened outside of Africa.
Factors contributing to Neanderthal extinction might include competition with modern humans, disease transmission, and climate change. The exchange of genetic material with modern humans provides immunity and vulnerabilities to various diseases, emphasizing the intricate relationship between these human species.