However, looking at the Denisovan genome allowed researchers to discern a greater amount of Neanderthal DNA in Asians and Native Americans than there is in Europeans. This suggests one of two things about how humans spread across the globe. First, it might mean that modern humans coming out of Africa formed families with Neanderthals in Europe, then their children slowly drifted to Asia. There, those mixed children formed families with other groups of Neanderthals in Asia, giving their children a higher percentage of Neanderthal DNA. Eventually, the offspring of these people traveled to the Americas, becoming the founder population for the peoples of North and South America.
A second possibility is that modern humans came to Europe out of Africa in two separate migrations. So they populated Europe, settling down with the Neanderthal locals. But then a new batch of modern humans arrived from Africa. When those new arrivals formed families with the mixed children of Neanderthals and Homo sapiens, it gave Europeans slightly more Homo sapiens DNA than other non-African people on Earth have today.
Regardless of what happened as different human groups came together in the lands beyond Africa, one thing remains certain. All of us share some genetic traits that set us apart from our hominin cousins. And a set of those traits could bear directly on how we think. "It makes a lot of sense to speculate that what had happened is about connectivity in the brain, because . . . Neandertals had just as large brains as modern humans had," Pääbo said. "Relative to body size, they had even bit larger brains [than Homo sapiens]. Yet there is, of course, something special in my mind that happens with modern humans. It's sort of this extremely rapid technological cultural development that comes, large societal systems, and so on." In other words, our brains weren't bigger than other hominins' brains. They were just wired differently.