Humans and other hominids have a reputation for bringing about mass extinctions. Homo erectus has been blamed for the disappearance of many African carnivores, our ancestors likely caused the Pleistocene extinctions, and modern humans are currently embroiled in the midst of the sixth great extinction event.
New evidence indicates that hominids have been causing significant extinctions far earlier than ever thought. Australopithecus afarensis, of Lucy fame, has been implicated in the disappearance of 23 species of carnivores that prowled Africa around 2 million years ago. Omnivores and small to mid-sized carnivores all bowed out at the same time tool-using A. afarensis showed up, leaving only hyper-specialized carnivores such as lions and hyenas.
Lars Werdelin, of the Swedish Museum of Natural History, theorizes that Australopithecines were such efficient scavengers that they knocked out any species that relied on part-time carcass theft. Groups of A. afarensis with stone tools likely were enough to scare away civets or large, predatory otters that competed for meat. This finding is all the more the remarkable becuase Australopithecines' brains and bodies were only slighter larger than those of modern chimpanzees. Human-style social living and tool use, it seems, have made us top competitors from the beginning.