Homoplasy in the evolution of modern human-like joint proportions in Australopithecus afarensis
Catherine K Miller, Thomas Cody Prang, Jeffrey Spear, Scott A Williams & Jeremy M DeSilva 2021 eLife
doi org/10.7554/eLife.65897

The evolution of BPism & reduced reliance on arboreality in hominins resulted in larger lower vs upper limb joints.
The pattern & timing of this transition, however, remains unresolved.
Here, we find:
- the limb joint proportions of Au.afarensis, H.erectus & H.naledi resemble Hs,
- those of Au.africanus, Au.sediba, Par.robustus, Par.boisei, H.habilis & H.floresiensis are more ape-like.
The homology of limb joint proportions in Au.afarensis & Hs can only be explained by a series of evol.reversals, irrespective of differing phylogenetic hypotheses:
the independent evolution of Hs-like limb joint proportions in Au.afarensis is a more parsimonious explanation.
Overall, these results support an emerging perspective in hominin paleo-biology: Au.afarensis was the most terrestrially adapted australopith, despite the importance of arboreality throughout much of early hominin evolution.
____

Not "terrestially", of course, but walking: this article once more confirms our view of parallel or convergent evolutions incl. reversals in E // S.African apiths (Hum.Evol.1990,1994,1996), but als in SE.Asian H.floresiensis.
Today, only Hs & hylobatids could be called "BP", but most Miocene Hominoidea were already "BP": frequent wading upright in swamp forests + climbing vertically in the branches above the water.
This explains in Hominoidea (vs Cercopithecoidea):
- broad breast-bone (Hominoidea=Latisternalia) & thorax (+ dorsal scapulas, facilitating lateral movements),
- broad pelvis (facilitating lateral leg movements?),
- lumbar spine: shorter (only c 5 vertebras) & more centrally-placed (upright),
- complete tail loss (hinder in wading? infection risk?).
Google "aquarboreal".