More people are doing home DNA genetic testing. Sometimes the results have been surprising. Interestingly, several people have told me they have a small percentage Neanderthal DNA. Although I initially thought that this finding was an error, I am now convinced that it was correct: I had to investigate this further.     Modern humans, Neanderthals, and Denisovans all shared a common ancestor called Homo heidelbergensis. Between 300,000 and 400,000 years ago, one g