Monday, March 5, 2018
Virginia Commonwealth University anthropology professor Amy Rector Verrelli, Ph.D., just returned from a research trip to Ethiopia where she served as part of the Ledi-Geraru Research Project that in 2013 discovered a fossil of the earliest member of the genus Homo, pushing back the origin of humans’ genus to 2.8 million years ago.
Rector Verrelli, an assistant professor of anthropology in the School of World Studies in the College of Humanities and Sciences, was one of a team of researchers from Arizona State University, Pennsylvania State University, George Washington University and the University of Nevada, Las Vegas hunting for fossils in the Afar region of Ethiopia, between the Ledi and Geraru rivers.
“It has deposits that are between about 1 million and 3 million years ago, so the goal is to look for fossils of our ancestors from that time period,” Rector Verrelli said. “In that area, that usually means Australopithecus afarensis (famous for the Lucy skeleton), but in 2013 project scientists discovered the earliest member of our genus, the genus Homo.”
Researchers in 2013 found a partial hominin mandible with teeth from the Ledi-Geraru research area, thereby establishing the presence of Homo between 2.8 million and 2.75 million years ago. The find extended the record of recognizable Homo by at least a half-million years, shedding new light on human evolution.
As part of the fieldwork for this trip — the first since 2015 — paleontologists searched for fossils while geologists mapped the sediments and looked for layers they could date to know how old the fossils were.
“My specialties include monkey and antelope fossils, so my job was to survey with other project members — basically going to the areas where we know the age of the fossils, and looking for things that we can identify,” Rector Verrelli said. “Once we find them, we take GPS information, give each fossil a bar code, and collect it to take back to the museum in the capital of Ethiopia, Addis Ababa.”
The most exciting days, she said, were those when they discovered hominins, or fossils from species of human ancestors.
“I was super lucky and found two hominin teeth this year — my first hominins ever, and I've been working in Africa looking for hominin fossils for 19 years!” she said. “On those days, as we're driving the Land Cruisers back into camp, we all sing and honk the horn and everyone still in camp comes out to sing and celebrate with us.”
The team received visits from scientists from universities and museums in the United States, Sweden, Germany, South Africa and Ethiopia. It also was supported by local team members from the Afar region who are particularly good fossil hunters.
Baro’o, a survey worker from the Afar region who worked closely with Rector Verrelli, found a tooth from a canid, a species in the dog family, that was one of the biggest ever found in Africa. “We’re not sure what species it was from yet,” Rector Verrelli said.
All of the team’s finds were fascinating, Rector Verrelli said, but especially fossils of antelopes, which can reveal much about paleoenvironments, or what the environment looked like at the time of early humans. “So it was always exciting to find an identifiable tooth or part of a horn,” she said.
Rector Verrelli joined the Ledi-Geraru Research Project in 2004. While she has worked in museums on fossils from Ledi-Geraru since 2014, this is the first time she has been back in the field since 2004.
Next year she will be one of the permit holders for the area — making her one of only a handful of women permit holders in Ethiopia — and will be one of the principal investigators for grants they will write for funding to return.
“The goal will be to go back every year, survey in areas with time periods of interest, and build a picture of what life was like for early Homo and Australopithecus afarensis as they evolved in the area,” she said.
Rector Verrelli’s work with the project fits within her larger body of research into reconstructing paleoenvironments of our ancestors, and asking questions about why they evolved the adaptations they did when they did.
“I get at these questions from a few directions,” she said. “I look at communities of animals that lived together during a certain time period, and I also have some projects reconstructing behaviors of fossil monkeys and interpreting how those behaviors fit into the overall paleoecological context. I have been working on the monkey community from the Ledi-Geraru and nearby deposits for years, and have reconstructed paleoenvironmental variation for Australopithecus afarensis and hominin species in a different genus, Paranthropus, for several projects as well.”
The goal will be to go back every year, survey in areas with time periods of interest, and build a picture of what life was like.
Rector Verrelli is interested in large-scale paleoenvironmental and biogeographic patterns, and working in the Ledi-Geraru area contributes data points for both of those questions, she said.
The project’s work, she added, is providing new and valuable insights into early human evolution.
“Our lineage has been unique since an ape species started walking on two legs some 6 million or 7 million years ago, and the evolution of all the species in this lineage has shown us that our family tree is more of a bush, with species living together and dividing up resources at the same time during different time periods,” she said.
For Rector Verrelli, understanding what the environment must have looked like for humans’ ancestors is not only fascinating, it can reveal what evolutionary pressures led to more efficient walking on two legs, the use of stone tools, and symbolic thought.
“For a long time, paleoanthropologists assumed that the genus Homo was something special and different, and meant big brains and complex communication. But what we find is that the earliest members of our genus, like the individual found in Ledi-Geraru, aren't so different from our apelike ancestors Australopithecus,” she said. “So what were the key adaptations that eventually led to what we think of as being human? And what was the environment like when those key adaptations evolved?”