Even in deepest darkest Africa, it seems that there’s only room for a small range of large carnivorous omnivores, once one of these species starts getting hyper-efficient. Evidence is building that competition even with pre-Homo hominins accounted for the extinction of many of these species. Ann Gibbons takes up the story:

After comparing fossils of 78 species of carnivores that lived during five different periods of time between 3.5 million years ago (when large carnivores were at their peak) and 1.5 million years ago, Werdelin found that all but six of 29 species of large carnivores (animals that weighed more than 21.5 kilos) had gone extinct in that time. Moreover, the mass extinction began just before H. erectus appeared in the fossil record 1.9 million years ago. He also found that the community of carnivores alive 2.5 million to 2 million years ago ate a much broader range of food—with species within a community filling a wider range of dietary niches. By 1.5 million years ago, just hypercarnivores that ate only meat, such as lions and leopards, had survived while omnivores that scavenged and ate a wider range of foods, like civets, had disappeared. “Even I was surprised by the dramatic drop,” Werdelin says.

Full report: http://news.sciencemag.org/sciencenow/2012/04/wheres-the-beef-early-humans-took.html?ref=em