And the evidence is becoming almost undeniable that a large comet or small asteroid struck North America about 12,500 years ago, and it was an Earth-changing event.
I don’t think it’s unreasonable to think that things like asteroid impacts, ice ages, etc, caused some extinctions. Like I said to another poster, though, just because you can find evidence of one thing causing some extinctions, doesn’t mean it or a similar event caused all of them. An asteroid could account for some extinctions in North America, and man could still be responsible for other extinctions. History’s too complex to say either asteroids or men caused them all.