Brief communication: Early hominin variability in first molar dental trait frequencies.

This report documents greater variability in early hominin first molar dental trait frequencies than previous research indicated. Specifically, frequencies of several M1 dental traits that previously appeared to uniquely characterize Paranthropus are shown here to resemble those of the A. afarensis sample from Hadar. Like Paranthropus, A. afarensis from Hadar has a high frequency of cusp 6 and a low frequency of the protostylid. Paranthropus and A. afarensis are also not statistically significantly different in their frequencies of LM1 cusp 7, although this cusp is actually absent in the latter. Both groups differ significantly from A. africanus in their frequencies of these traits. Based on the developmental biology of molar cusp patterns, we suggest that the morphological similarities between Paranthropus and the Hadar sample may be homoplasies.