During the end of the last great Ice Age, the climate at Rancho La Brea transformed from being humid and cool to the one that exists today. Year-around streams and ponds that once existed, slowly began to dry out.

One of the mysteries that surround the animals at Rancho La Brea is the extinction event that made many of these animals disappear forever. This extinction event was not like those that have been labeled as "mass extinctions." Unlike the dinosaurs that were wiped out by a large and destructive worldwide event, the causes of the extinctions at Rancho La Brea were much more subtle.

The main theory for this extinction process is a combination of the slow changing events that took place in North America during the short window of time about 12,000 years ago. Climate and weather changes resulted in a drastic shift in the types of plants that grew in prehistoric of Rancho La Brea. The change in plant life had an impact on the herbivores' food supply, which in turn had a direct effect on the carnivores that preyed on them.

This "domino effect" within the food chain was probably the major cause of the extinctions, but was most likely accelerated by the humans that were beginning to live in North America during the end of the Pleistocene. There is strong evidence to suggest that even if a small human population in North America hunted mammoths and other large herbivores on a limited basis, it would have greatly sped up the extinction process that was already occurring.

A Clovis Point is a fluted point of stone made by some of the first inhabitants of North America some 11,000 years ago. Its exact use is unknown, but some researches believe that the Clovis people may have used them for hunting.

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