Figure 4.

Comparison of proportional toe depths of chimpanzee, human and Laetoli G1 footprints. Proportional toe depth was calculated as maximum depth in the toe region divided by maximum depth in the heel region, following an earlier published study [14]. To aid in visualization of the box plots, three extreme outlying human data points are not included (those proportional toe depths are equal to 10.34, 10.79 and 25.03). Post hoc pairwise t-tests (with Bonferroni correction) show that footprints produced by two chimpanzees (n₁ = 24 and n₂ = 21) and the Laetoli G1 hominin (n = 5) have significantly shallower proportional toe depths than do the footprints of 41 modern humans (n = 245). The chimpanzee and Laetoli G1 samples do not significantly differ from each other. This result demonstrates that, contrary to previous hypotheses [14,15], the Laetoli G1 footprints are compatible with a more flexed limb posture than is typical of modern humans.