Yep. DNA. And the Cherokee are one of the few tribes who are RH negative too. hmmm
This from The Journal of Experimental Medicine:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2135301/
more:
http://www.rhesusnegative.net/staynegative/wp-content/uploads/2016/07/Pollitzer_et_al-1962-American_Journal_of_Physical_Anthropology.pdf