The influence of mass,volume and density on the frequency of recovery of fossil hominid hand and wrist bones

A study of the mass, volume and density of each of the wrist and hand bones of male and female human skeletons was undertaken. It was found that the mass and volume (i.e. size) of the bones are well correlated with the relative frequencies of preservation ofAustralopithecus and earlyHomo wrist and hand bones from fossil hominid sites in Africa. In general, the larger the bone, the greater its preservation frequency. In contrast to findings on bovid bones, the density of hand and wrist bones is not well correlated with the frequency of such bones recovered from these sites. These findings may be explained in terms of the agents of deposition of the bones, the physical nature of the deposit, and the methods of extraction of the fossils from the deposit.     

Mechanical advantages of the Neanderthal thumb in flexion: a test of an hypothesis

It has been proposed that the pollical phalangeal length proportions of the Neanderthals provided them with a greater mechanical advantage relative to recent humans for their pollical flexor muscles in power grips across the interphalangeal (IP) joint at the expense of the mechanical advantage of those pollical flexor muscles in precision grips at the finger tip. To test these related hypotheses, we compared the pollical load arm dimensions (phalanx lengths) to power arm dimensions (dorsopalmar articular heights) for the European and Near Eastern Neanderthals and for European and Amerindian samples of recent humans. It was found, initially, that the proximal articular height of the pollical distal phalanx is a poor predictor of the power arm at the IP articulation, even though the proximal articular height of the pollical proximal phalanx was an adequate indicator of the power arm size at the metacarpophalangeal (MCP) joint. In addition, differences in distal pollical ulnar deviation at the IP joint appeared to make little difference in the mechanical advantage comparisons. More importantly, the relative shortness of Neanderthal proximal pollical phalanges and the relative lengthening of their distal pollical phalanges was confirmed, and it was determined that, despite some minor differences in articular dimensions between Neanderthals and recent humans, these pollical phalangeal length contrasts translated into significant differences in mechanical advantages for the flexor muscles across the MCP and IP articulations.     

The differential frequency of preservation of early hominid wrist and hand bones

A survey of hominid hand and wrist bones of Plio-Pleistocene fossil hominid sites in Africa was undertaken. There are 101 specimens in total, from 7 sites. Carpals are most rarely preserved, but certain elements such as the capitate tend to be more frequently preserved than others. There is a preservation rate cline from proximal to distal in the hand, proximal elements (metacarpals) being numerically better preserved than the distal elements (proximal, middle and distal phalanges, in that order of preservation). The proportion of complete, or nearly complete hand and wrist bones is greater in the distal than in the proximal elements. There is no statistical difference in the frequency of preservation of left and right sides, or in the frequency of preservation of proximal and distal ends of individual bones, although there is a tendency for proximal ends to occur more frequently than distal ends. The incidence of hand and wrist bones in fossil deposits is low compared with that of other post-cranial skeletal elements (with the exception of foot bones, where the incidence is similar). This could be accounted for by depositional factors, but preparation techniques and differential collection of specimens may play a role.