Read this thread or at least the last three posts.
I have also often thought about how many people were killed in the meteorite that caused the Barringer Crater, 50,000 years ago. (In Arizona) That must have played the devil with all living things in North America, huh?
That has bothered me as well, ever since I've known about the overpressure shock wave these events produce. This one would have been equivalent to a 20-40 megaton airburst...