Painted shapes

David Anastasio Explores the Possibility of an Alternate Route of Human Migration

David Anastasio’s examination of ancient lake sediments clarifies ages of human migrations out of northern Africa.

Story by

Carina Sitkus

Photography by

Illustration by Luke Best

David Anastasio’s collaborative research project has potentially significant implications for our understanding of how early humans migrated from Africa and the subsequent peopling of Europe—and it began with the discovery of an old tooth in a farmer’s nightstand in southern Spain. 

Anastasio, a professor of earth and environmental sciences, was conducting research on mountain formation and landscape changes in southern Spain when he and a fellow geologist, Josep Parés from the Spanish National Lab of Human Evolution, took a detour to collect rocks from the Guadix-Baza Basin, the site of the largest ancient lake in Europe. Near the small Spanish village of Orce, they revisited the site of a tooth found in the basin, which the farmer’s son rediscovered after his father’s passing. 

“The question became ‘how old is this tooth?’ And I said, ‘I think I have an angle that could let us figure it out,’” Anastasio says. 

The resulting project includes collaborators from the Lab of Human Evolution and the University of Granada, among others. 

Painting of person with tractor

Human artifacts found in northern and southern Spain, Anastasio explains, provide important clues about the path and timeline of human migration. A common theory claims the earliest Europeans traveled an eastern route around the Mediterranean Sea, through Israel and Jordan, but an alternative route out of northern Africa, through Gibraltar and into southern Spain, gives the tooth and stone tools found in the basin great significance. 

Using rock magnetic cyclostratigraphy, magnetic polarity stratigraphy, and electron spin resonance dating, the team of researchers is dating the archeological remains found around the basin. These combined approaches are necessary to date early human remains that are likely more than one million years old, says Anastasio.

This combination of dating methods will date the human artifacts and surrounding lake sediments to within 20,000 years. Anastasio's use of cyclostratigraphy, the study of astronomically driven cyclic variations within the sedimentary record, was both serendipitous and novel.

“I have been using the record of the magnetism in rocks as a way of figuring out their concentration of dust,” Anastasio explains, joking that in the mid-2000s he noticed his house was dusty and then he happened to attend the talk of a scientist who was tracking Siberian dust in ice to measure melting glaciers on Greenland. It occurred to Anastasio that atmospheric dust varies with climatic conditions and accumulates in sediments and rocks. He taught himself to take the necessary measurements using a colleague’s lab equipment and found that there was a cyclic pattern of this environmental variability. 

“So one of the things I've been doing for the last 15 years is using this kind of cyclic behavior to determine how fast sediments are accumulating to study tectonic processes,” says Anastasio.

Now he is applying the same techniques to date archeological sites. Looking at the rocks that surround the human artifacts, Anastasio can analyze how much time is gathered in the layers of sediment and their relationship to the layer where an ancient tooth was found to determine its age. 

Monica Powers ’20 helped collect and analyze the data. There is still some disagreement between the various methods, Anastasio explains. The goal of the next stage of research is to collect more data to reconcile these differences. 

“By establishing the ages of these human remains, then you can start asking anthropological questions about why you think humans migrated this way,” says Anastasio. “[And] in frontier science, you're trying to sort out the methods while you're trying to sort out the answers.” 

David Anastasio’s research focuses on structural geology and tectonics. He received his Ph.D. from Johns Hopkins University. 

Story by

Carina Sitkus

Photography by

Illustration by Luke Best

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