On Thursday, September 22, 2022 at 8:53:43 AM UTC-4,
littor...@gmail.com wrote:
Human ancestor had small thumbs
Fossil analysis reveals that a Hs ancestor(sic - but Lucy was apparently a fossil relative of Gorilla) would have made a terrible hitch-hiker.
Past reconstructions of the hands of the hominin Au.afarensis assigned scattered bones to individuals & single fingers.
Campbell Rolian (Univ.Calgary Canada) & Adam Gordon (SU NY Albany) re-analysed an assembly of Au.afarensis bones to better account for uncertainties in the fossil record.
Their results suggest:
the hominin(sic) had shorter thumbs than was thought, with proportions more closely resembling gorillas.
Although Au.afarensis may have been able to bring the tips of its fingers & thumbs together, its thumbs were not long enough for the precision grip that later hominins used to craft stone tools.
Reassessing manual proportions in Australopithecus afarensis
Campbell Rolian & Adam D Gordon 2013
Am J Phys Anthropol 152:393–406, 2013
doi org/10.1002/ajpa.22365
Previous analyses of afarensis hand morphology have concluded:
it had Hs-like manual proportions: rel.long thumbs & short fingers.
These conclusions (based on the A.L.333 composite fossil assemblage from Hadar) are premised on the ability to assign phalanges to a single individual, and to the correct side & digit.
Neither assignment is secure, however, given the taphonomy & sample composition at A.L.333.
Our re-sampling approach (incl. the entire assemblage of complete hand elements at Hadar) takes into account uncertainties in identifying phalanges by individual, side & digit nr.
This provides the most conservative estimates of afarensis manual proportions.
We re-sampled hand long bone lengths in Au.afarensis & extant hominoids,
we obtained confidence limits for distributions of manual proportions in the latter.
Results confirm:
afarensis intrinsic manual proportions are dissimilar to Pan & Pongo,
but often fall at the upper end of the distribution in Gorilla (very lower end in Homo): disproportionately short thumbs & long medial digits in Homo.
This suggests:
afarensis manual proportions (particularly metacarpal proportions)
- were not as derived towards Homo (as previously described),
- rather are intermediate between gorillas & humans.
These results suggest:
Au.afarensis could not produce precision grips with the same efficiency as Hs,
this may in part account for the absence of lithic technology in this fossil taxon.
____
Lucy was obviously a fossil relative of Gorilla.
Only anthropocentrically biased PAs believe Lucy was our ancestor.
Google "aquarboreal ancestors".
Why would you expect otherwise? Humans have increased thumb length vs early Homo. Slow brachiation did not strongly select for change in thumb length, but fast brachiation strongly selects for very short thumbs and long hooklike fingers.
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