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The Manipulative Complexity of Lower Paleolithic Stone Toolmaking

Figure 3

Probability distribution (or relative frequency or proportion of total time) of joint angles for 18 joint angles of the left hand during Oldowan (blue dots) and Acheulean (red dots) toolmaking.

Solid lines are Gaussian distributions with mean and standard deviation matched to the empirical joint angle histograms. Plots have a logarithmic vertical axis, such that the data and the matching Gaussian distributions appear as parabolas. The configuration of the hand was determined by the following joints (from left to right, top to bottom): the carpo-metacarpal (ThumbTMJ), metacarpal-phalangeal (ThumbMPJ) and interphalangeal (ThumbIJ) joint angles for the thumb and the abduction angle (ThumbAbduct) between the thumb and the palm of the hand, the metacarpal-phalangeal (MPJ) and proximal interphalangeal (PIJ) joint angles for the four fingers, the three relative abduction angles between the four fingers (MiddleIndexAbduct, RingMiddleAbduct, PinkieRingAbduct), as well as the arching and bending (during flexion/extension, ulnar/radial deviation) of the palm surface with respect to the wrist (PalmArch, WristPitch,WristYaw). Note, the joint angle zero is relative to the joint angle on our calibration splints.

Figure 3