Craig Feibel

PROFILE

For more than 25 years Craig Feibel has conducted research in East Africa in order to establish a geologic framework and an environmental backdrop to the evolutionary and archaeological record for which that region is so famous.

Using the tools of geology – stratigraphy, sedimentology, and paleontology – Feibel works to characterize both the environment at a given moment and how it changed through time.

“You can look at a point in time and you know basically what the landscape was like as a setting for an assemblage of stone tools or the bones of those who made them,” Feibel said. “We try to answer questions about what kind of world they were they living in, or how it changed through time, and how those changes might have influenced things like community dynamics, ecology, and the evolutionary process.”

His work begins with the stratigraphy, identifying the layers that constitute the record of geological history. This is fieldwork – walking, examining exposed deposits, describing them and collecting samples for laboratory analysis of their makeup and the fossils they might contain.

Recently, Feibel has been studying snails and tiny crustaceans known as ostracods embedded in the strata. This may seem far removed from human evolution, but these creatures offer a treasure trove of information about context.

“We can get a very interesting picture of changes in the chemistry of the water and, in this case, it often tells us about shifts in the monsoon system,” Feibel said. “You can detect patterns of regional rainfall, which affect the growth of plants and trees that are ultimately the basis of the whole ecological system.”

Feibel and his colleagues do a lot of work on dating and geochemistry, trying to assign ages to local sequences and thereby enabling other scientists to know the age of their sites. The prehistory of East Africa is one of successive volcanic eruptions. There are about 150 different layers of volcanic ash identified chemically in the Lake Turkana area where Feibel works, but perhaps only 30 have been dated. The problems the scientists face are far from simple and will require a lot more work to resolve.

Context – its spatial aspect, sequence, age models, and environment – is as important, or even more important than the fossil finds themselves, Feibel argued.

“A huge amount of the true value of hominid fossils and artifacts, particularly in understanding what they mean, comes from putting them into this context,” he said. “To develop this frame of reference for evolutionary events is important to understand what we are as organisms – to know what it was like out there when we developed.”