For eight hours a day last summer, Juliet Brophy examined ancient teeth, jammed together with colleagues into a small room affectionately dubbed the “tooth booth” at the University of the Witwatersrand in South Africa.
Brophy, an assistant professor of anthropology at LSU, was just one of scores of researchers trying to understand the offerings of a rich fossil find the year before deep in a South African cave system.
What they found by sifting through the 1,550 fossil pieces was a major discovery announced earlier this month: a new ancient human ancestor called Homo naledi.
Researchers believe they identified at least 15 members of this new species, which had characteristics of both modern humans and more ancient ancestors in the human family tree. The new species is a member of the Homo genus, making it a distant ancestor, but an age has yet to be identified, which means experts can’t say exactly where this group lies in the evolution to Homo sapiens.
“If it comes out to be under a million (years old), the classic line is, ‘Our family tree is bushier than we thought,’ ” Brophy said.
For Brophy, being selected among hundreds of applicants to help analyze the find was an exciting chance to work with researchers from around the world to decipher such a huge collection of fossils. The sheer number of fossils that were discovered is rare.
“All we knew is there was a large collection of fossils to be analyzed,” she said.
Discovered by recreational cavers in 2013, the fossils were anything but easy to get to. After descending through a stretch of cave, there is a small opening that forces a person to crawl through a space less than 10 inches high. That opens into a larger cave, at the top of which is another narrow passageway that then drops into the chamber where the fossils were found.
Unlike other fossil areas, these weren’t buried or encased in hard rock. Bones were lying everywhere, making it difficult to know where to step, Brophy said.
Lee Berger, with the University of the Witwatersrand in South Africa and the lead researcher, put out a call for early-career scientists to help analyze the large find. Brophy applied and was accepted.
Brophy said the after-hours discussions among the large group of researchers raised more questions than answers as they tried to piece together what they had found. One of those mysteries is what all of these individuals were doing in this remote cave location.
Because of the concentration of fossils, and because it is very difficult to get to the part of the cave system where they were found, it’s thought that the individuals were brought to the place deliberately. Researchers are avoiding the term “burial” because that has cultural connotations that go beyond what is known. However, there are no marks to indicate the bodies were brought to the place by animals and no signs that water flushed the bodies into the caves during a flood.
Species often have to be identified by just a few fossils, but this time, not only were there hundreds of fossils found, but there were also many different examples of each fossil, which gave a much more complete picture.
For example, imagine the only bone found was a femur. There’s no way of knowing if that represents the species as a whole or if the individual was short, tall, malformed or typical.
With multiple examples of the same part, researchers could better determine if what they were seeing was normal and get a better picture of what the species as a whole looked like.
In this case, Brophy and her co-workers had 190 teeth to examine, which is unprecedented when talking about other species finds. At first, the teeth needed to be described and classified by shape and size. Next, the researchers looked for characteristics such as shape or placement of particular teeth in the mouth that would indicate if the teeth had more modern characteristics or more ancient ones.
For example, the teeth of this new species were relatively small, which is a modern trait. However, Homo naledi’s back teeth were the largest, which is more primitive.
Because of the tough enamel in teeth, they have a better chance of surviving the ages and are the most common fossil found, Brophy said.
Although the teeth, hands, wrists and feet looked very much like what would be found in humans, the pelvis, shoulders and femurs were more primitive, according to the article that was posted to eLife Sciences Publications.
The new species goes against the previously held belief that a small brain and large teeth go together since as brains got larger, teeth could get smaller because of improved use of technology like fire to cook food.
However, Homo naledi has a small brain and small teeth.
“We know a lot less than we thought we did,” Brophy said.
And there’s more to discover. The cave where these fossils were found contained so many that the excavation had to just focus on a small part so that analysis could start, Brophy said.
“The concentration is so dense that there’s more fossils than sediment in some areas,” she said. “It will be really interesting to see what else is down there.”
Follow Amy Wold on Twitter, @awold10.