The pleistocene overkill hypothesis vs. the climate argument

Were the Clovis responsible for the extinction of the pleistocene megafauna?  These exotic and gloriously large creatures used to populate North America.  How did they all manage to disappear 10,000-11,000 years ago, so shortly after the arrival of the Clovis?  The ongoing debate about this is just as contentious as the "Clovis first" debate.

The pleistocene overkill hypothesis claims that these untold numbers of native animal species were hunted and slaughtered to extinction by man alone.  It reasons that the Clovis arrived to find a glut of big game, and using the technology of their spear points and throwers, they were able to become Superpredators.  Furthermore, the gluttonous slaughtering of these unknowing animals happened so quickly that the animals never had the time to develop a fear of humans and save themselves.  (After all, animals develop fear of humans for good reasons - if they have no legitimate reasons, they won't run from them).  Excavations of Clovis-associated kill and camp sites have produced the bones of a variety of big game including mammoths, bison, horses and bears.  After driving this mass extinction and exhausting their resources, the Clovis themselves were replaced by several more regional paleoindian groups (such as the Folsom).

Those who reject the pleistocene overkill hypothesis as the root cause of the mass extinctions of the North American megafauna point to the drastic changes in climate that occurred at the end of the Pleistocene.  Natural habitats changed rapidly during this time as the climate became much drier and warmer.  It is probable that many species were weakened by these changes and either died off or were killed off due to their vulnerability.  The fact that the Pleistocene extinction was so widespread and devastating points to a large-scale catastrophe of some sort - perhaps a long-term drought.  Throughout the history of the planet, mass extinctions have occurred, and although their causes are unclear, it is projected that they are largely correlated with significant climatic changes.  This appears to be a normal component of the planet's cycles.  However, in the case of the North American pleistocene megafauna, there is no doubt that the paleoindians who hunted them were somehow instrumental in their rapid demise.

Some North American pleistocene megafauna:

http://nationalhumanitiescenter.org/tserve/nattrans/ntecoindian/essays/pleistocene.htm