Thursday, June 13, 2019
The period between 2.5 million and 3 million years ago was critical in the evolution of our ancestors. Three million years ago, there were multiple species of Australopithecus — a group of extinct primates — across eastern and southern Africa. By 2.5 million years ago, that group had mostly died out, and in its place had evolved two separate lineages: Paranthropus and our own genus, Homo.
Paranthropus lasted over 1 million years and was represented by three species with dental and facial adaptations for potentially eating tough or hard foods. Human beings’ lineage, Homo, is characterized by a pattern of increased brain size and dependence on material culture that has persisted over the past several million years.
While this period is considered critical in understanding the evolution of early humans and human ancestors, it is poorly represented in the fossil record and few fossil specimens have been found that can shed light on the causes and patterns of the origins of these lineages.
The National Science Foundation awarded a $390,000 collaborative grant to a team of researchers, including Amy Rector, Ph.D., an assistant professor in the Department of Anthropology in the School of World Studies in the College of Humanities and Sciences. The team is conducting research at the Ledi-Geraru site in the Afar region of Ethiopia that aims to shed new light on the extinction of Australopithecus and the emergence of Homo and Paranthropus.
“This grant will support our efforts to explore an important time period in human evolution: when our genus, along with a closely related ancestral ‘cousin,’ first evolved and began using Oldowan [simple stone] tools,” Rector said. “What's so exciting is that this time period between 3 and 2.5 million years ago is rarely preserved in the fossil record so right now paleoanthropologists know very little about why and how these lineages evolved, but we have materials from this age at Ledi-Geraru. And already the fossils and tools are showing us how important this time period is.”
The oldest fossil from the genus Homo — a 2.8-million-year-old mandible — was discovered at the Ledi-Geraru site, and a recently published paper announced that the oldest Oldowan stone tools had been found in the team’s research area.
Along with Rector, collaborators on the Ledi-Geraru Research Project include Brian Villmoare, Ph.D., at University of Nevada, Las Vegas; J. Ramón Arrowsmith, Ph.D., Chris Campisano, Ph.D., and Kaye Reed, Ph.D., at Arizona State University; Erin DiMaggio, Ph.D., at Pennsylvania State University; and David Braun, Ph.D., at George Washington University.
“Our team, along with our team in Ethiopia, will be searching for fossils and stone tools that date to between about 3 and 2.5 million years ago,” Rector said. “We’ll also be analyzing our finds for information like environmental reconstructions, isotope evidence of climatic conditions, and how stone tools were made and used. Our geologists have created extensive and precise maps of the region, so they will also be working to better understand how the landscape has changed over time and influenced the evolution of our ancestors and their behaviors.”
Rector said she hopes the team’s work will help illuminate humanity’s early origins.
“This time period between 3 and 2.5 million years ago is critical — we know the genus Homo evolved, we know stone tools changed, and we know our cousin lineage, Paranthropus, evolved. But in almost every site in Africa, sediments from this time period are missing because of geological processes like erosion,” she said.
“Because Ledi-Geraru preserves this time period, we have the potential to learn more about what triggered the evolution of our own genus, and how climate and ecology may have influenced the evolution of ourselves and other ancestors on our family tree,” she said. “Because of the time period we’re sampling, each discovery could be something brand new.”