The dominant hypothesis is that Amerindian extirpation of 35 of 44 Pleistocene megafauna species rendered their immune systems unaccustomed to zoonotic diseases.
To which I would add that hunting the domesticable animals into oblivion seriously retarded agro-urban development and condemned many tribes to permanent seasonal nomadism.
“To which I would add that hunting the domesticable animals into oblivion seriously retarded agro-urban development and condemned many tribes to permanent seasonal nomadism.”
Yes. But bear in mind that New World beasts and “native” Americans were not coeval. Humans came over here fully prepared to hunt everything to death. The animals had not enough time to evolve defenses. Back in the Old World, there was time to breed (though not deliberately, of course) animals to our liking over the course of millenia.
Let’s get this straight and clear: the “native Americans” were cultural losers who got thrown out of Asia because they were some combination of losers, , antisocial, inadequate, socially caustic or retarded. Indians were (are) freaks.