In 1972, archaeologists working in Kenya unearthed a mystery: a partial skull with a long, flat face and a large cranium. For the first half of the 20th Century, scientists thought the evolutionary tree for modern humans (Homo sapiens) was pretty simple. We had evolved from Homo erectus on a fairly straight and branchless path, with evidence of only one other Homo species (dubbed Homo habilis) that predated and overlapped with Homo erectus. But the skull, known as 1470, suggested that there might have been another Homo species–a distant cousin of modern humans–living in Africa alongside our direct ancestor Homo erectus about 2 million years ago. With only one specimen to go on, scientists disagreed about whether 1470 truly represented a separate species or simply showed the range of variation in the previously known Homo species.
This week, scientists announced that they had found portions of three additional skulls, which appear to confirm that 1470 was not a complete anomaly and suggest that there were two additional Homo species living alongside Homo erectus. Our image of the week shows one of the new fossils, a lower jaw bone, fit together with 1470 (with the help of computer imaging).
Even with the new evidence, the debate continues about how many distinct Homo species were living in Africa between one and two million years ago. What is certain is that scientists have a new reason to closely examine the shape and complexity of our family tree.
Read more about the discovery in the New York Times, Science News, or the press release from the Turkana Basin Institute and National Geographic.
Written by Christine Hoekenga
Christine is a freelance writer, editor, and content strategist, specializing in science and nature. She holds an Bachelor's degree in Environmental Science and Media Studies and a Master's of Science Writing. She has been working in science communication and education for nearly a decade as a journalist, an organizer for conservation groups, and a museum educator. Before joining the Visionlearning team, she served as the New Media and Online Community Manager for the Webby award-winning Smithsonian Ocean Portal. Christine is assisting Visionlearning with developing new modules and glossary terms, managing the blog, and outreach through social media.