It looks like mankind's earliest ancestors go back a lot further than first thought. After 13 years digging in the Rift Valley region of Ethiopia, team of researchers have found a 2.8-million-year-old jawbone from our genus.
Creatures of the genus Homo were thought to have evolved around two million years ago, producing various evolutionary offshoots before modern humans, Homo sapiens, came along. The new find kicks the birth of Homo back 400,000 years.
"It's an excellent case of a transitional fossil in a critical time period in human evolution," said William Kimbel, director of Arizona State University's Institute of Human Origins.
"One of the persistent questions that people have, and not just specialists, but everyone wonders about where did we come from? And paleoanthropologists such as myself are dedicated to the mission of filling in the story of our origins through the finding of fossil evidence in remote places like Africa. That's where we go every year to do our research and we are rewarded this time with a very important specimen that answers one aspect of this pressing question."
The find is small – a tiny piece of jawbone from the left side of the face with five teeth embedded in it – but it tells us a huge amount about our time on the planet. The molars are small, typical of Homo species, and the bone contains a mix of ancient and more recent evolutionary features.
"The importance of the specimen is that it adds a data point to a period of time in our ancestry in which we have very little information," said Kimbel. "This is a little piece of the puzzle that opens the door to new types of questions and field investigations that we can go after to try to find additional evidence to fill in this poorly known time period."
The fossil is also a crucial missing link to the Australopithecus ancestors of humans. The partial skeleton of "Lucy," the most famous sample we have of that grouping, was found not far from this new find.
Rather pleasingly, the new fossil was found by Chalachew Seyoum, an ASU graduate student originally from Ethiopia. He found the jawbone while excavating on a ridge line and said he knew what the fossil was the moment he saw it.
"Honestly, it was an exciting moment," said Seyoum. "I had good experience in field surveying and knew where potential sediments are. I climbed up a little plateau and found this specimen right on the edge of the hill." ®