I would be very interested to read the actual paper if you can find it. It will not be a simple matter for the scientists to find any appropriate genes. NZ scientists are having trouble finding the difference between holstein and jersey cattle genes. They're working backwards by looking at the F2 and F3 hybrids.

The half million year's separation mentioned in the article is the mitochondrial DNA lines, about the time Homo heidelbergensis began their expansion.

The same mtDNA time scale puts the separation between cattle and bison as twice as long, a million years. Althoughn speciation is unlikely to be simply a function of time hybrids between cattle and bison are fertile. Incidentally, does anyone know anything about domestic cattle ever joining bison herds?

The myDNA evidence on its own is not sufficient to prove no Neanderthal genes survive in modern humans. It would be interesting to know how the scientists chose the genes they looked for. They would be unlikely to find Neanderthal genes in Africans or Polynesians for example. My bet would be that if they have concentrated on stocky Europeans with big noses, blond hair and a tendency for a bulge at the back of their skull they would raise their chances.