The mitochondrial DNA study indicated that there was no genetic input from Neanderthals in modern humans, but the whole-genome study suggests that, in fact, there was. One suggestion to explain this discrepancy is that the Neanderthal input into modern human populations was from males only. Which of the strategies could be employed to test this hypothesis? Look at genomic DNA only in modern humans that are male. Look at the X chromosome because that is bi-parentally inherited. Look at the Y chromosome because it is paternally inherited. Look at genomic DNA only in modern humans that are females.