Biomechanics of the human thumb and the evolution of dexterity
F.A.Karakostis cs 2021 Curr.Biol.31:1317-1325 https://www.cell.com/current-biology/fulltext/S0960-9822(20)31893-5 katerina.harvati@ifu.uni-tuebingen.de
* Increased thumb opposition efficiency was present c 2 Ma.
* This evol.advantage was less pronounced in Australopithecus.
* This dexterity is shared with all recent hominins, incl.Homo naledi. Systematic tool production & use is one of humanity’s defining characteristics, possibly originating >3 Ma.
Heightened manual dexterity is considered to be intrinsically intertwined with tool use & manufacture, critical for human evolution,
but its role in the emergence of early culture remains unclear.
Most previous research exclusively relied on direct morphol.comparisons between early hominin & modern human skeletal elements,
it assumed that the degree of a species’ dexterity depends on its similarity with the modern human form.
Here, we develop a new approach to investigate the efficiency of thumb-opposition, a fundamental component of manual dexterity, in several spp of fossil hominins.
Our work for the first time takes into account soft tissue & anatomy, integrating virtual modeling of musc.opponens pollicis & its interaction with 3D bone-shape.
Results:
a fundamental aspect of efficient thumb opposition appeared c 2 Ma, possibly ass.x our own genus Homo,
it did not characterize Australopithecus, the earliest proposed stone tool maker.
This was true also of the late Australopithecus species Au.sediba, previously found to exhibit human-like thumb proportions.
In contrast, later Homo spp (incl. the small-brained H.naledi) show high levels of thumb opposition dexterity, highlighting the increasing importance of cultural processes & manual dexterity in later human evolution.
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"cultural processes"??
Homo's "manual dexterity" = shellfish opening, cf. sea-otter?

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