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confident in both the age of the fossils and Brown's and Feibel's understanding of the history of the lake basin.

A major question in paleoanthro-pology today is how the anatomical mosaic of the early hominids evolved. By comparing the nearly contemporaneous Allia Bay and Kanapoi collections of anamensis, we can piece together a fairly accurate picture of certain aspects of the species, even though we have not yet uncovered a complete skull.

The jaws of anamensis are primitive—the sides sit close together and parallel to each other (as in modern apes), rather than widening at the back of the mouth (as in later hominids, including humans). In its lower jaw, anamensis is also chimplike in terms of the shape of the region where the left and right sides of the jaw meet (technically known as the mandibular symphysis).

Teeth from anamensis, however, appear more advanced. The enamel is relatively thick, as it is in all other species of Australopithecus; in contrast, the tooth enamel of African great apes is much thinner. The thickened enamel suggests anamensis had already adapted

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