As the debate over the origin of the human species rages on campus, a team of researchers that includes USF staff members has reported in the journal Nature they have found and identified the fossils of a 3.3 million-year-old human ancestor.
Jonathan Wynn and Diana Roman, both assistant professors of geology at USF, were on the team and were largely responsible for dating the specimen.
“What we found is a really remarkable specimen of the species Australopithecus afarensis, which is the same species that ‘Lucy’ belongs to.
“What is really interesting about this fossil is that it was found in a sandstone loch. It was sort of encased in sandstone, which means that it was preserved in really exquisite detail. What we typically have are maybe isolated fragments of bone that didn’t really survive very well. (This fossil) was buried as a corpse rather than being scattered across the landscape by carnivores.”
“Lucy” is another A. afarensis female that is geologically younger than this fossil, which has been called “Lucy’s Baby.” Wynn, however, prefers another name.
“It’s been called ‘Lucy’s Baby,’ but that is sort of a misnomer, because this fossil actually a few hundred thousand years older than Lucy. The name which I think is sticking better is Selam. In a lot of Ethiopian languages, selam means peace.”
The remains of Selam, who was 3 years old when she died, were found in the Dikika valley of Ethiopia in 2000.
According to Bernard Wood in his article “A Precious Little Bundle,” published in the same issue of Nature, “The fragile bones of infants rarely survive long enough to make it into the hominin fossil record. But if they do, they provide precious information about the growth and development of the individual and its species.”
The specimen was remarkably preserved, Wynn said.
“There’s a lot of detail in this particular fossil,” he said. “Parts of the brain case have fallen away, and they can be replaced back onto the brain case. What that does is exposes a lot of the details of the morphology of the brain. You can see what the shape of the brain is.”
Roman, a volcanologist, helped to date the fossil using a process called stratigraphy.
“Basically, every time you have a volcanic eruption,” she said, “each eruption has unique chemical signatures, so the chemistry of the ash is unique. Because of that, we can look at the ash and figure out how they correspond to a catalog of eruptions for which we know the age. So I have been looking at the chemistry of different layers buried around the hominid. We can use these ash layers to basically bracket the age of the fossil.”
The Dikika valley is close to a large amount of Placticine volcanic activity, and both researchers look forward to going back into the field in November.