The adaptive and classificatory significance of certain quantitative features of the forelimb in primates



Quantitative osteological features of the primate brachium and antebrachium can be defined in relation to functionally significant contrasts in the principal muscle blocks. Such features, as shown by univariate and multivariate statistical study of a total of 525 sets of arm bones from 39 primate genera, demonstrate a broad correlation with the extent to which the forelimb is subject to tensile forces during locomotion. Man, in different features, resembles contrasting groups of non-human Primates; in sum total of such characteristics, he is unique.

Other dimensional characters, defining more general features of the arm bones differentiate individually, but more especially in multivariate combination, between major taxonomic groups within both Prosimii and Anthropoidea.

In combination, the two groups of dimensions give a separation that is primarily taxonomic but which has a locomotor underlay.

When, in sum total, the dimensional characters of the arm are combined with those of the shoulder (where, as established in earlier work, the separation produced is almost exclusively locomotor), the initial division is in accordance with locomotor function of the forelimb—and especially the extent to which the limb is subjected to tensile forces. But there is a strong taxonomic underlay.

A method is thus provided for enquiry into both the taxonomic and functional significance of arm bones of fossil Primates.

The work, in addition to endorsing the classical concept of Man's retention of primitive mobility in the distal segments of his forelimb, also re-emphasizes his uniqueness through arm mobility being associated with shoulder action principally caudal and ventral to the joint.