A totally invalid study. There is no control group study cited. For example, Indian tribes of the west had no big cities; yet they were continually raiding each other`s villages and killing each other off, stealing hostages etc., espcially after they had horses. Comanches especially were very efficient at killing off all their Indian neighbors, leaving sometimes no survivors. They took no prisoners. They had the whole Great Plains to themselves after a few years of death by tomahawk etc. skull cracking etc.
These researchers have to go back and take “Methods of Ancient Anthropological Population Research 101’ .. .My cat is smarter than these morons.
I bet that American Indian remains are pretty difficult to find. Sparse populations and spread out across the mountains and prairies. Plus, I’m not sure if the Indians were around during climate change, which appears to be the primary factor in these head wounds.