November 8, 2011
Luck plays a big role in fossil hunting. Some of the most significant fossils for the study of human evolution were found by accident. In 1924, rock quarrying in South Africa uncovered the first Australopithecus. In the Republic of Georgia, archaeologists found some of the oldest evidence of hominids outside of Africa, dating to 1.8 million years ago, while excavating a medieval fortress in Dmanisi in the 1980s.
Once a rich fossil site is unearthed, researchers tend to revisit it over and over again, because looking for new fossil sources can be time-consuming and expensive, requiring researchers and their assistants to carefully walk across large expanses while keeping an eye out for fragments of fossils or artifacts sticking out of the ground. But with the rise of satellite technology and geographic information systems—or GIS, computer systems that allow researchers to integrate, analyze and model various types of geographic and spatial data—paleoanthropologists are beginning to look for new field sites while sitting at their computer desks.
For example, last year, paleoanthropologists Jackson Njau and Leslea Hlusko, both of the University of California at Berkeley, explained in the Journal of Human Evolution how they used high-resolution satellite imagery and Google Earth to locate 28 previously unknown archaeological and/or hominid fossil sites in Tanzania. Tanzania’s most famous fossil sites—including Laetoli and Olduvai Gorge—occur in large outcrops of sedimentary rock. Njau and Hlusko thought fossils were probably also hiding in smaller, more difficult to find outcrops scattered throughout the country.
The researchers combed satellite imagery, looking for particular patterns of erosion that would help expose fossils and reflectance patterns characteristic of sedimentary rock. Different types of landscapes reflect different wavelengths of electromagnetic radiation, which satellites record. On satellite maps, sedimentary rock appears to be bright white. After identifying these features, Njau and Hlusko considered how much vegetation was growing in the vicinity and how accessible the area was, in order to narrow down possible locations to visit. Sifting through the satellite images before hitting the ground allowed the pair to more efficiently find fossil sites—some of which may not have been found had the researchers not considered previously neglected areas.
Another example shows how GIS can allow researchers to search for old hominid migration routes as a way to figure out where fossils might be. In this case, a group of researchers—Charles Egeland of the University of North Carolina at Greensboro, Christopher Nicholson of the University of Wyoming and Boris Gasparian of the National Academy of Sciences of the Republic of Armenia—was interested in finding more evidence of the earliest hominid dispersals out of Africa. They wanted to search in Armenia, just over the border from Dmanisi, Georgia, where some of the oldest evidence of this early exodus is recorded.
But where to look in Armenia? The team reconstructed a possible route from Africa to Dmanisi. Assuming hominids left the continent through the Sinai Peninsula, Egeland and his colleagues used Israel as a starting point and modeled a “least cost path,” the easiest way to travel to Dmanisi based on challenges posed by modern terrain. (Information on ancient environments is not yet detailed enough to plug into such models.) Their path cuts across Syria and southeastern Turkey before following the western border of Armenia and finally crossing northwestern Armenia into Georgia. Based on this route, they narrowed their search to northwestern Armenia and zeroed in on the Debed River Valley, based on its proximity to ancient lake deposits (hominids liked living near water, as people do today) and volcanic deposits (useful in radiometric dating). Next, they created a “suitability” map for this region of Armenia, using a variety of landscape characteristics. Suitability was determined from the features of previously discovered hominid sites in the country; for example, such sites are most often near rivers, with open vegetation and flat terrain.
The final step was to explore promising areas and dig. In 2009, the team found 25 new archaeological sites of varying ages in the Debed River Valley. Two of the sites contained Oldowan tools, the earliest known tools and the type likely made by the first hominids that left Africa. They reported their finds last year in the Journal of Ecological Anthropology (PDF).
These are just two examples of successful high-tech fossil hunting. Many more are likely to follow. But no matter how useful computers become, they won’t replace human fossil hunters anytime soon.
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