In a new study, a research team led by Yale University found that even the oldest known human ancestors may have had precision grip capabilities comparable to modern humans. This includes Australopithecus afarensis, which appears in the fossil record a million years before the first evidence of stone tools.
Manual dexterity is traditionally viewed as a key adaptation that separated the earliest primates from other early mammals. It is thought that such abilities evolved in response to no longer needing hands for locomotion, as well as the mechanical demands of using tools.
Yet there remains debate about the gripping capabilities of early fossil hominins, especially regarding the use of tools. The new study may shed light on some of those issues. For instance, the study suggests that the early human species Australopithecus afarensis may have had greater dexterity than what was required for cutting with a stone, including manipulative and tool-related behaviors that may not have been preserved in the archaeological record.
See also: Human origins: The war of trivial explanations (including for bipedalism)
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Here’s the abstract:
Primates, and particularly humans, are characterized by superior manual dexterity compared with other mammals. However, drawing the biomechanical link between hand morphology/behaviour and functional capabilities in non-human primates and fossil taxa has been challenging. We present a kinematic model of thumb–index precision grip and manipulative movement based on bony hand morphology in a broad sample of extant primates and fossil hominins. The model reveals that both joint mobility and digit proportions (scaled to hand size) are critical for determining precision grip and manipulation potential, but that having either a long thumb or great joint mobility alone does not necessarily yield high precision manipulation. The results suggest even the oldest available fossil hominins may have shared comparable precision grip manipulation with modern humans. In particular, the predicted human-like precision manipulation of Australopithecus afarensis, approximately one million years before the first stone tools, supports controversial archaeological evidence of tool-use in this taxon. – T. Feix, T. L. Kivell, E. Pouydebat, A. M. Dollar. Estimating thumb-index finger precision grip and manipulation potential in extant and fossil primates. Journal of The Royal Society Interface, 2015; 12 (106): 20150176 DOI: 10.1098/rsif.2015.0176 (paywall)