First, a mathematical simulation model (16) was interpreted as showing the North American megafauna most likely succumbed to over-hunting after human colonization at the end of the last Ice Age.
However, some elegant recent studies have demonstrated that prey from a diverse range of phylogenies can rapidly develop vigilance to completely novel predators (see refs. We conclude that models alone cannot resolve the question of whether the megafauna were hunted to extinction because of the critical importance of numerous assumptions, many of which may never be amenable to validation.
A great variety of competing scenarios have been proposed to explain the extinction of the megafauna such as climate change, disease, altered habitat condition (particularly due to the effects of landscape burning by humans), and the breakdown of food webs (3, 10, 11), but the presently ascendant idea is the so-called overkill hypothesis.
This theory posits that extinctions were exclusively a result of human hunting (12), with a popular variant being the most restrictive case (termed “blitzkrieg”), where the extinction phase occurred within a few thousand years of human colonization (9, 13).
Indeed, the demise of the megafauna is often packaged as an environmental morality tale (8, 9).
No matter why the debate interests people, there is no doubt that it is of great significance.