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

Paleo-Indians

The Clovis people belong to the Early Paleoindian period.  Paleo means "old."  These paleoindians arrived in the Americas on foot at the end of the period of history known as the Pleistocene.  They crossed Beringia from Asia, traversing from the "old world" to the "new world."  At that time, what is now the Bering Strait was a landmass 1,000 miles across at its widest.  Once reaching what it now Alaska, these paleoindians either traveled south along the coastal route or east along rivers and through mountain passes.  All along this journey to the new world, the paleoindians encountered multitudes of animal species, including many species of megafauna (animals over 100 lbs.).  These exotic animals all became extinct shortly after the arrival of the paleoindians.  Did these early humans hunt these animals to extinction?

Human migration

For a visual journey of the human migration route - The Bradshaw Foundation and Stephen Oppenheimer's Journey of Mankind

Clovis first?

The "Clovis first" theory holds that people spread throughout the Americas only after the Last Glacial Maximum, as it would have been humanly impossible to journey across the ice sheets prior to the large corridor opening up.  As this corridor opened up, passage from what is now Alaska through Canada to the rest of the Americas became possible.  However, radiocarbon-dated evidence of earlier human habitation has been found, notably with artifacts from the Monte Verde site in Chile predating any Clovis artifacts by at least 1,000 years.  There is strong evidence of a coastal migratory route that predated the opening of the ice corridor about 12,000-13,000 years ago.  After all, if people populated the southern tip of South America by 11,000 years ago, they most likely began their journey long before this opening occurred.  Evidence suggests that after crossing Beringia (what is now the Bering Strait) the earliest humans headed south down the west coast of the Americas.  This migratory route is believed to have moved faster than that of the Clovis people traversing North America.  The Clovis first theory remains a hotly debated issue.

Who were the Clovis people?

Although a highly contentious issue among anthropologists, the reigning opinion is that the "Clovis" people were the first inhabitants of North America, arriving after the Last Glacial Maximum (which was 18,000 years ago).  They are called the Clovis people because the first discovery of the bone and ivory projectile points they are known for was made at an archeological site in Clovis, New Mexico.  These points have subsequently been discovered in many sites in the U.S., and the oldest artifacts have been reliably dated to be 11,500 radiocarbon years old (translating to roughly 13,500-13,000 calendar years ago).  The Clovis were big-game hunters of megafauna who would attach these fluted points to the end of wooden spears to bring down their game.  They appear to have been constantly on the move, as they never built any permanent structures or dwellings, making their way steadily across the continent.  They left little evidence other than a few (known) campfire hearths and butchering sites, scattered across the Americas.