Figure 4
From: The implications of thumb movements for Neanderthal and modern human manipulation
Illustration of potential TMc joint motion in the recent modern human (first column) and for the Neanderthal sample. The modern human specimen lies at the negative extreme end of the first PLS axis (Fig. 3A). This modern human specimen shows the other bones articulation with the trapezium (Trpzi) and the first metacarpal (Mc1), the scaphoid (Scp), trapezoid (Trpzo) and second metacarpal (Mc2). Each column corresponds to the suggested direction of trapezial-Mc1 joint motion (following50) for one specimen. The bones are shown in neutral position (turquoise) and in motion (grey). Directions of motion are internal (Int +) and external (Ext −) rotation (red), in adduction (Add +) and abduction (Abd −) (yellow), as well as flexion (Flex +) and extension (Ext −) (orange). For each motion direction of force transmission from the Mc1 to the trapezium is suggested based on the covarying morphology (white arrow). The trapezial-Mc1 joint is surrounded by a strong complex of ligaments and tendons6,33, which is not considered in this illustration, as we don’t have these soft tissues for fossils. Rotational movements are not shown here. The illustration is not scaled.
