Final answer:
The best model to explain the presence of Neanderthal genes in modern humans is interbreeding between Neanderthals and early modern humans. Genetic evidence shows that most modern-day Europeans and Asians have inherited about 1-4% of their DNA from Neanderthals.
Step-by-step explanation:
The best model to explain why modern humans have 1-4% Neanderthal genes is the theory of interbreeding between Neanderthals and early modern humans. Genetic evidence shows that interbreeding occurred between the two species, resulting in the presence of Neanderthal DNA in modern human populations.
Recent studies have found that most modern-day Europeans and Asians inherited about 1-4% of their DNA from Neanderthals. This genetic exchange likely took place as modern humans migrated out of Africa and encountered Neanderthals in Europe and Western Asia.
The presence of Neanderthal genes in modern humans has been linked to various traits and diseases, including cranial structure, metabolism, skin morphology, and cognitive development.