““crunching. The amount of introgression from Neanderthals is proportionally lower on the modern X than on the rest of the chromosomes. X chromosomes are only passed on by males half of the time because we also have a Y, but all of the time by women, who have two Xs. The observation that there is less Neanderthal DNA on our Xs implies that the first encounters we had with them that resulted in procreation were male Neanderthals with female Homo sapiens.””
