Op maandag 8 augustus 2022 om 07:41:47 UTC+2 schreef Primum Sapienti:
> DD'eDeN aka note/nickname/alas_my_loves wrote:
> > On Tuesday, August 2, 2022 at 1:23:16 AM UTC-4, I Envy JTEM wrote:
> >> DD'eDeN aka note/nickname/alas_my_loves wrote:
> >>> They were moving on two legs [on horizontal tree branches]. Bipedalism is the most
> >>> ancient human [hominoid] adaptation. It's what happened first.
The earliest hominoids already became vertical:
wading bipedally + climbing arms overhead in the branches above the swamp (coastal?) forest.
This is obvious: Miocene apes:
- became larger (secondarily reduced in hylobatids),
- lost the tail: very drastic & unexpected for arboreal tetrapods, but not for aquarboreal tetrapods,
- got very wide bodies: pelvis, thorax & sternum (Hominoidea=Latisternalia): lateral arm & leg movements for aquarborealism (& possibly + surface-swimming),
- reduced the lumbar spine, but got "sacralisation" = vertical stabilisation,
- evolved much longer arms: they had to climb in the branches above their heads.
But *why* did they become aquarboreal?
The simplest hypothesis is this:
when the Indian continent approached Eurasia (plate tectonics), island arcs were formed initially,
these islands had plenty of (*only* initially) coastal forests:
the first Catarrhini that reached these islands, had to become aquarboreal (aqua=water, arbor=tree) =
hominoid/cercopith split (or ape/OWM split) c 30 Ma.
But after many mill.yrs, when India went further underneath Eurasia, this automatically split eastern & western aquarboreals
= lesser/great ape split c 20 Ma:
- the hylobatids followed the SE.Asian coastal forests,
- the others colonized the western Tethys coastal forests.
But c 15 Ma, the Western Tethys Ocean split: this Mesopotamian Seaway Closure divided
- the sivapiths-pongids (East): forced the hylobatids higher into the trees,
- the dryopiths-hominids (West): colonized the Tethys=Med.Sea coastal forests,
both branches had inland side-branches along rivers/bais/swamps...
Some hominids colonized the Red Sea Rift, the others died out (climate? MSC?).
When the E.Afr.Rift formed c 8 Ma, these hominids split into
- Gorilla-Praeanthropus: Lucy afarensis->boisei etc.
- Homo-Pan initially remained in the Red Sea (still largely a Rift then?),
but when the Zanclean flood c 5.3 Ma re-filled the Med, it probably also filled the Red Sea, which opened into the Ind.Ocean:
- Homo went left (S.Asian Indian Ocean coasts) -> our Pleistocene littoral ancestors,
- Pan-Australopith.s.s. went right (E.Afr.Ind.Ocean coasts):
Taung africanus->robustus evolved in parallel (allopatrically) with // afarensis->boisei knuckle-walking etc.
Very simple & (bio)logical...
In any case, only incredible imbeciles believe their ancestors ran after antelopes over Afr.savannas.