ASU part of international team to study links between climate, geology, human evolution

Arizona State University researchers will help lead a $1.2 million, multi-institution project that will use a new theoretical framework and state-of-the-art technology to tackle a long-standing question: How did ecological factors millions of years ago affect the evolution of our ancestors?

The possible answers so intrigued the W.M. Keck Foundation that it awarded the international team one of its largest grants to explore this question.

The funds will support a systematic, integrated investigation into why two adjacent, world-renowned fossil study areas in the Afar region of Ethiopia — Hadar and Woranso-Mille — have revealed strikingly different records of our human genus’s early predecessors.

ASU’s Institute of Human Origins has a more than 40-year history of exploration and discovery in Hadar, starting with the 1974 discovery of “Lucy,” the 3.2-million-year-old Australopithecus afarensis fossil, by the institute's Founding Director Donald Johanson. Since then, scientists have found hundreds more fossils of Lucy’s species at Hadar, but no other hominin species that might have lived at the same time.

Only 30 miles north of Hadar, a research project at Woranso-Mille that began in 2005, led by the institute's new director, Yohannes Haile-Selassie, has yielded ample fossils from not only Lucy’s species, but at least two others — including one whose foot appears to be adapted to tree climbing. Some of these different species existed at the same time.

Haile-Selassie and Kaye Reed, a research associate with the Institute of Human Origins and President’s Professor with the School of Human Evolution and Social Change; Beverly Saylor of Case Western Reserve University; and Naomi Levin of the University of Michigan are co-principal investigators on the W. M. Keck Foundation awarded project. Case Western Reserve University is the lead institution for the award.

Other participating institutions include Addis Ababa University, Aix Marseille University, University of Barcelona, Berkeley Geochronology Center, Ohio University and the University of Southern California. 

Haile-Selassie and Reed will lead efforts to compare and analyze the fossil record from Hadar and Woranso-Mille to assess links between rift setting, landscape-scale heterogeneity and mammal diversity, including among hominins.

“This multidisciplinary integration of physical, chemical and biological evidence will enable us to assess differences in the ecology of closely related early human ancestors and provide insights into the origins of our own genus,” said Haile-Selassie, who is a professor with the ASU School of Human Evolution and Social Change.

The transformative aspect of this project is that it is attempting, for the first time, to directly compare Hadar and Woranso-Mille to examine the environmental selective pressures that might have driven human evolution.

Seizing this opportunity involves engaging some 30 scientists whose expertise ranges from geology and paleoanthropology to geochronology and paleoclimate, including Christopher Campisano, Institute of Human Origins research associate and associate professor in the School of Human Evolution and Social Change; David Feary, research professor in the School of Earth and Space Exploration; and Denise Su, who will join the Institute of Human Origins and the School of Human Evolution and Social Change as a research associate and associate professor in August.

Over the next three years, the team will gather samples and data from both areas to gain a more detailed understanding of the two sites as they existed more than 3 million years ago.

Reed will refine the reconstructions of habitats using fauna, isotopes and depositional data for specific areas within the Hadar stratigraphy and work with Su to compare the differences in mammals and habitats between the two sites.

“This is the first time we have the opportunity to compare the paleoecology of unique fauna and hominins from adjacent areas in the same time period,” Reed said. “It will give us a level of detail that we haven’t had and enable us to explore why there were different species living close together but not overlapping spatially. It’s very exciting.”

Campisano will lead the geologic efforts at Hadar, guiding and working with a team of geoscientists that are new to Hadar to collect high-resolution samples and data at particular time intervals to compare to Woranso-Mille.

“Better integrating Hadar’s geology and paleoenvironments with adjacent project sites has been a goal of mine for more than a decade,” Campisano said. “The chance to do this, and with a suite of new-to-Hadar analytical techniques, is an intriguing opportunity.”

Su will primarily be responsible for the reconstruction of the paleoenvironment at Woranso-Mille using the faunal evidence and integrating the geologic, isotopic and paleobotanic data.

“Woranso-Mille is the only Pliocene site that documents at least two contemporaneous hominin species. Reconstructing its paleoenvironment will be crucial to understanding how the hominins shared the landscape,” Su said.

Rounding out the ASU team is Feary, who will be developing a high-resolution 3D model of the Hadar focus area using recently developed aerial photogrammetric techniques as a base for the geological and habitat reconstructions.

“The W.M. Keck Foundation award provides an amazing opportunity to use new research tools to address fundamental paleoenvironmental and human evolution questions,” Feary said.

If successful, this project will reveal the spatial context of hominin diversity records — one of the great challenges to understanding human evolution and a fundamental question of biodiversity. 

“This project builds on decades of field studies, laboratory analyses and museum work, that together with the differences in hominin species in neighboring but distinct geological landscapes provide an unprecedented opportunity to understand the ecological characteristics that influence human diversity and evolution,” said Saylor, who is the lead investigator on the project.

Haile-Selassie added, “This project takes human origins research to another level. Understanding how tectonics and rifting may have played a role in the diversity or lack of diversity in early human ancestors, and how these forces may have shaped the landscapes and associated climates in which our earlier ancestors diversified or went extinct would be a major breakthrough in paleoanthropology.” 

Ethiopia’s Authority for Research and Conservation of Cultural Heritage and the Afar Regional Government will be facilitating local permits for this research.

Julie Russ
jruss@asu.edu