Sunrise on the Serengeti, and life on the savanna is in full swing. Zebras and wildebeests graze the dewy grass; elephants and giraffes munch on acacia leaves; and lions and hyenas survey the scene, looking for their next meal. To visit this place is, in some ways, to see the world as it looked to our ancestors millions of years ago, long before humans began to wreak havoc on the planet—or so the conventional wisdom goes. Indeed, much of eastern Africa is often thought of as a pristine ecosystem, largely unchanged by our kind in the more than two million years since our genus, Homo, arose.
But new research paints a rather different picture of this supposedly unaltered place. In my studies of the fossil record of African carnivores, I have found that lions, hyenas and other large-bodied carnivores that roam eastern Africa today represent only a small fraction of the diversity this group once had. Intriguingly, the decline of these carnivores began around the same time that early Homo started eating more meat, thus entering into competition with the carnivores. The timing of events hints that early humans are to blame for the extinction of these beasts—starting more than two million years ago, long before Homo sapiens came on the scene.