I wonder if the Neanderthals were the first blonde cave women?
Maybe a mutant red head?
Probably closer to the truth than some would care to believe..
Consider the following..
It's generally accepted that the "races" of modern man in the northern climates developed lighter skin (loss of melanin) to absorb more sunlight, producing needed vitamin D..
Likewise, the northern humans body hair changed to fine and straight, in order to better preserve body heat..
Neanders, having survived 2 Ice Ages, ( they were around for 200,000 years! ) probably also had light skin and fine, straight body hair..
Evolution itself may account for sufficient change in DNA structures to account for the lack of present evidence of Neander / Human assimilation..
Although many like to claim the DNA "Eve" as the first human, that's not really the case..
She's just all the farther we can go back by tracing mtDNA..
There were probably hundreds, if not thousands of other mtDNA lines that have simply died out and can no longer be traced back to their origins.
The same may be true for Neanderthal..