Final answer:
Paabo's team found that non-African human genomes contain about 1-4% Neanderthal DNA due to interbreeding between early humans and Neanderthals after humans left Africa.
Step-by-step explanation:
Paabo's team concluded that approximately 1-4% of the genome of non-African humans came from Neanderthals. Genetic studies confirm that Neanderthals interbred with early modern humans when the latter moved out of Africa and into areas such as Europe, where Neanderthals had already established themselves. This exchange of genetic material led to modern European and Asian populations inheriting Neanderthal DNA, which is reflected in the slightly greater similarity of their genomes to the Neanderthal sequence when compared to those of African descent.