The sophisticated manipulative skills that characterize modern humans (Homo sapiens) have been related to our derived hand morphology (for example, long thumb relative to fingers, robust joints and hypertrophic pollical muscles) which allows for combined power and uniquely among hominids pad-to-pad precision grasping.
Commonly, these modern human-like (MHL) grips and linked MHL manual anatomy are interpreted as specific adaptations for the efficient manufacture and use of stone tools, another purported hallmark of ‘humanness’. However, as the hominid fossil record expands, a complex pattern of hand evolution is now apparent: the hand bones of some Pliocene Australopithecus are actually more MHL than are those of other, more recent Pleistocene hominins, suggesting that systematic manufacture and use of stone tools could well have emerged in hominins that already possessed skillful hands.
The earliest tools, associated functionally with butchered ungulate bones, are dated to 2.6-million-year-old and, even older, 3.3-Ma lithic artifacts have also been recently announced. Thus, although the fossil record indicates that Pliocene hominins possessed overall MHL hand proportions and probably advanced manipulatory skills, most available post-cranial evidence of this period (including hand bones) also reflects adaptations consistent with habitual engagement in arboreal locomotion.
Indeed, it is only <2 Ma that key regions of the hominid post-cranial skeleton exhibit fully MHL morphologies which may indicate an adaptive commitment to a terrestrial MHL lifestyle. The new Olduvai Hominin (OH) 86 manual proximal phalanx, described here and dated to >1.8 Ma, enriches our understanding of this critical period of transition to a more MHL body form in our ancestors.
Domínguez-Rodrigo, M. et al 2015