If you'll recall, I wasn't arguing for the "hunting-only" theory - I was arguing that a combination of factors is likely the key. I do, however, believe that hunting was *one* of them, but that hunting alone would never have caused such widespread extinctions.
I do, however, think that you underestimate the value to a society of a megafauna kill. I don't have figures for mammoths, but after watching a show about the Donner party and cannibalism, they mention that the average adult male human has about 4.5 lbs of protein, enough for 60 people for one day. Assuming a 180lb human and a 8 ton mammoth, with simply scaling these figures up by body mass, we're looking at about 400 lbs of protein, feeding a whopping 5,400 people for a day (or more realistically, a smaller number for notably longer). Do you have more precise figures (also addressing things like calorie consumption)?
Also, where did you get that sloth meat is bad? It's eaten in some parts of South America.
I would argue that the reason some of North America's large mammals survived is that a steady state was reached before extinction. Early humans were no more migratory than many other predators, especially without horses. If left in a fairly stable environment for long enough, most species tend toward equilibrium. Not only do the buffalo, for example, adapt, but also do the social values of the native tribes. They are selected apon - through natural selection - based on their ability to not kill off all of the food supply in the area.
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"Illuminant light,
illuminate me."