As australopithecines remained more or less unchanged for two million years, this shows that they were very well adapted to their environment. So what forced their evolution into Homo?

Australopithecines were successful only because of their association with cats. The lost of the use of cats would force australopithecines as a species to change or die. Cats also remained unchanged during this period which shows that they too were well adapted. I believe that cats were so successful due to their association with australopithecines that their population increased beyond the environment's carrying capability. The end of the Pliocene is marked by the Malthusian collapse of the cat population.

This may have been due to disease caused by overcrowding, but there is evidence that it was due to overhunting. Henry Wesselman has done research that shows that the micro-mammal fauna, rodents and other small mammals, under went a sudden population collapse and shift in species types. Cats ate themselves out of business.

No longer able to obtain food, shelter or protection from cats, most australopithecines died out. Only the bigger and the smartest managed to survive. Some entire species of cat using australopithecines were unable to adapt and so Australopithecus africanus quickly went extinct. The plant eating robust australopithicenes were not as dependent on cats as the graciles, as so were able to hold on longer, but in the end, A. robustus and A. boisei met their doom. Only a small group of gracile australopithecines in East Africa were able to adapt and change. The chaotic morphologies of Homo rudolfensis, H. habilis, H. microcranous, H. ergaster and other hominines of this period so odd that they can not be assigned to a species show a creature under severe evolutionary pressure.

Eventfully, out of this transitional period, Homo erectus emerged, a species fully adapted to life without cats. With its larger size, stone weapons and most of all fire, H. erectus could have provided for their own food and defense; and would have no need to sleep in trees. Indeed, its large size would no doubt have prevented erectus from taking advantage of static cling. H. erectus had no need for cats.

Copyright © Lorenzo L. Love
August 8, 1998