Without that comparison it's hard to say that the difference between modern DNA and that of the ancient farmers means current people are descended from the ancient hunter-gatherers.
'In this particular case, the reason may be because of a farmer input that was subsequently diluted, assuming that the N1a haplotype is a marker of spreading farmers, and that it was as rare in pre-Neolithic Europe as it is today,' Zilhao said.
But, he added, 'I see nothing in the data that would necessarily carry the exclusion of, for instance, the opposite hypothesis . . . that (the N1a marker) represents the incorporation of hunter-gatherer females in the farming communities that are coming into Europe about 7,500 years ago, that incorporation being in such small numbers that, eventually, it all but disappeared.'"