There is only one species of hominid on the planet today: modern humans, or Homo sapiens. But for most of the last seven million years, a variety of hominid species typically inhabited Earth at the same time. Different species sometimes lived in the same region and shared the same resources. Human evolution, long thought to be a linear progression in which each new species replaced an older one, now appears to have taken a more complicated path.

The African Savannah Illustration by Jay H. Matternes

Around two million years ago, at least four different kinds of hominids lived around Lake Turkana, in what is now northern Kenya. The lakeshore was then lined with brackish lagoons, and the surrounding forests gave way to more open country on the drier soils.

The three species shown to the right all date from between 1.6 and 1.9 million years ago. Although similar in age, these three species are quite diverse. The oldest specimen, from the species Kenyanthropus rudolfensis (top), is notable for its relatively large brain compared to earlier hominids. The slightly younger specimen of the species Paranthropus bosei (middle) had a massive battery of chewing teeth. And the 1.6-million-year-old Turkana Boy, belonging to Homo ergaster (bottom), had a body essentially like that of modern humans—tall stature, long legs and short arms. These three species, as well as the early toolmaker known as Homo habilis, all foraged around the shores of Lake Turkana in what is now Kenya.