I'm thinking that the viable variations in early Sapiens, Sapiens/ Sapiens, Neanderthalis were few, and so the differences between our population today and then would be small as there are few working combinations in the genome "lock" as it were. Was the study done between hybridised Sapiens, Sapiens populations vs Sapiens, Neanderthalis, or non hybridised vs. Sapiens, Neanderthalis?