YDP
I was under the impression that the Overkill theory was losing ground to the Younger Dryas Impact theory which blames a series of airburst meteors over the Americas around the 10,900 BP mark that put paid to much of the Mega Fauna so the appearance of these folk as many as 16,000 years earlier is hardly a case of overkill, unless they were having a population explosion after several milennia.