Ostrich Eggshells Tell Time

Ostrich eggshells may turn out to be one of the world's most valuable time pieces. Alison Brooks, a research associate at this Museum and professor of anthropology at George Washington University, discovered that fossilized ostrich eggshells can be used to date archaeological and fossil sites up to 10 million years old. Early humans in Africa used the shells for beads, cooking vessels and water carriers, and shell fragments are the only identifiable animal fossils left at many sites.

From the moment an ostrich egg is laid, its amino acids (the building blocks of proteins) begin changing from one form to another. Brooks measured the amount of this breakdown. With this information and the temperature history of a site, she can determine the age of the eggshells--and the surrounding objects.

So What?
Many ostrich eggshell fossils come from a time when modern humans were evolving--sometime between 40,000 and 200,000 years ago. There are few reliable dating methods for that period. So these fossils may provide one of the best means of dating human origins.

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