Summary<p>Using DNA from two ancient humans unearthed in two different archaeological sites in northeast Brazil, researchers have unraveled the deep demographic history of South America at the regional level with some surprising results. Not only do they provide new genetic evidence supporting existing archaeological data of the north-to-south migration toward South America, they also have discovered migrations in the opposite direction along the Atlantic coast -- for the first time. Among the key findings, they also have discovered evidence of Neanderthal ancestry within the genomes of ancient individuals from South America.