For the first time scientists have looked at the Y chromosomes of modern humans, Neanderthals, and Denisovans, giving us yet one more piece of the puzzle. The common ancestor of humans (by which I mean modern humans), Neanderthals, and Denisovans lived between 500,000-800,000 years ago. What this means is that there was a total replacement of the Neanderthal Y chromosome with a human Y chromosome. The “healthier” Y chromosome from a human could have had a selective advantage over the existing Neanderthal Y chromosome, and came to predominate. In short, each aspect of these different hominid populations (modern humans, Neanderthals, and Denisovans) have different lineages all with their own histories – their nuclear DNA, Y chromosomes, mitochondrial DNA, and tool culture.