Op dinsdag 22 november 2022 om 17:38:01 UTC+1 schreef Daud Deden:

> The Origins of Bipedal Locomotion
> William EH Harcourt-Smith 2013
> Handbook of PA doi 10.1007/978-3-642-27800-6_48-3
> Abstract
> Bipedalism is a highly specialized and unusual form of primate locomotion that is found today only in modern humans. [DD: Sifaka, Hylobatidea, All known Homo spp.] The majority of extinct taxa within the Hominini [DD: Hominoidea] were [DD: arboreal] bipedal, but the degree to which they were bipedal remains the subject of considerable debate. The significant discoveries of fossil hominin remains in the last 40 years have resulted in this debate becoming increasingly focused on how bipedal certain fossil taxa were, rather than on the overall process. Although the early hominin fossil record remains poor, evidence points to at least two distinct adaptive shifts. First, there was a shift to habitual [DD: arboreal] bipedalism, as typified by certain members of Australopithecus, but possibly including earlier genera such as Ardipithecus and Orrorin. Such taxa were [DD: arboreal] bipedal, but also retained a number of significant adaptations to arboreal climbing. The second shift was to fully obligate bipedalism [DD: Sifaka, Hylobatidae, Homo are all obligate bipeds.] and coincides with the emergence of the genus Homo [DD: No, of course not.]. By the Early Pleistocene, certain members of Homo had acquired a postcranial skeleton indicating fully humanlike striding bipedalism [DD: No chin so they must have had a different striding gait & weight distribution than modern humans]. The final part of this chapter reviews why bipedalism was selected for. [DD: Bipedalism long preceded the advent of Homo sapiens.] There have been many theoretical explanations, and the most robust remain those linked to the emergence of more varied habitats. Such an environmental shift would have involved strong selection for new behavioral strategies most likely linked to the efficient procurement of food. [DD: Such as better access to arboreal fruits and nuts]

I mostly agree with DD, but IMO we should specify: early-hominoid BPism was less walking-climbing BPism than wading-climbing BPism: Miocene Hominoidea lived in swamp forests (most likely in coastal forests in S-Eurasia along the Tethys Ocean), where they frequently waded bipedally (upright) in the shallow water between the trees, and often climbed arms overhead in the branches above the water. This explains best in apes:
-complete tail loss,
-very broad sternum, thorax & pelvis + dorsal scapulas (also lateral movements of arms & legs),
-centrally placed lumbar spine, with 5 rather than 7 lumbar vertebras, etc.
This locomotion has been called (google) "aquarboreal" (aqua=water, arbor=tree).

Thank you for reviving this thread, Marc. I hope you are still monitoring it,
because I have a lot of comments to make on what Daud wrote, and on some that you added,
and I'm curious to see what you think about them.

You might not know that Daud announced here in s.b.p. about two
months ago that he was taking a vacation from here and also from sci.anthropology.paleo.
So don't expect any responses from him any time soon.

On Friday, March 17, 2023 at 3:31:05 PM UTC-4, marc verhaegen wrote:
> Op dinsdag 22 november 2022 om 17:38:01 UTC+1 schreef Daud Deden:
> > The Origins of Bipedal Locomotion
> > William EH Harcourt-Smith 2013
> > Handbook of PA doi 10.1007/978-3-642-27800-6_48-3
> > Abstract
> > Bipedalism is a highly specialized and unusual form of primate locomotion that is found today only in modern humans. [DD: Sifaka, Hylobatidea, All known Homo spp.]

This was a very valid correction by Daud. I don't know whether he includes Indris or Avahis
under "Sifaka", but they too are bipedal. There may be something about Madagascar, where
all three of these other primates originated, that encourages bipedal locomotion.

> > The majority of extinct taxa within the Hominini [DD: Hominoidea] were [DD: arboreal] bipedal,

Here, OTOH, Daud was introducing a separate theme and not necessarily disagreeing.

Do you see it that way too, Marc?

> > but the degree to which they were bipedal remains the subject of considerable debate. The significant discoveries of fossil hominin remains in the last 40 years have resulted in this debate becoming increasingly focused on how bipedal certain fossil taxa were, rather than on the overall process.. Although the early hominin fossil record remains poor, evidence points to at least two distinct adaptive shifts. First, there was a shift to habitual [DD: arboreal] bipedalism,

Here, too, Daud was not necessarily disagreeing; here, though, he was adding details
to the locomotion method rather than expanding the range of taxa.

> > as typified by certain members of Australopithecus, but possibly including earlier genera such as Ardipithecus and Orrorin. Such taxa were [DD: arboreal] bipedal, but also retained a number of significant adaptations to arboreal climbing. The second shift was to fully obligate bipedalism [DD: Sifaka, Hylobatidae, Homo are all obligate bipeds.] and coincides with the emergence of the genus Homo [DD: No, of course not.].

I'm not sure, but I think the author, William EH Harcourt-Smith, was only interested in the lineage
leading up to Homo, and may have thought that bipedalism was independently acquired by
Hylobatidae, as it seems to in the case of the lemurs mentioned above. Or he may have thought
that bipedalism was temporarily lost in our lineage, and then regained.

> > By the Early Pleistocene, certain members of Homo had acquired a postcranial skeleton indicating fully humanlike striding bipedalism [DD: No chin so they must have had a different striding gait & weight distribution than modern humans].

I do not see how the word "must" is justified by "No chin." Do you, Marc?

> > The final part of this chapter reviews why bipedalism was selected for.. [DD: Bipedalism long preceded the advent of Homo sapiens.]

See above about "lineage."

> > There have been many theoretical explanations, and the most robust remain those linked to the emergence of more varied habitats. Such an environmental shift would have involved strong selection for new behavioral strategies most likely linked to the efficient procurement of food. [DD: Such as better access to arboreal fruits and nuts]

Here is where you came in, Marc:

> I mostly agree with DD, but IMO we should specify: early-hominoid BPism was less walking-climbing BPism than wading-climbing BPism: Miocene Hominoidea lived in swamp forests (most likely in coastal forests in S-Eurasia along the Tethys Ocean),

I've known about your wading-climbing hypothesis for over a year now, Marc, but
I don't recall anything about the location. In fact, I just had Africa in the back of my
mind when I read what you and Daud and Mario had written about it.

It's an interesting amplification: is it possible that our lineage goes back to SE Asia before
moving to Africa? or should I say, back to Africa? [Recall Proconsul and Ekembo, 17 to 20mya,
predating Ramapithecus/Sivapithecus by about 5my.]

> where they frequently waded bipedally (upright) in the shallow water between the trees, and often climbed arms overhead in the branches above the water. This explains best in apes:
> -complete tail loss,
> -very broad sternum, thorax & pelvis + dorsal scapulas (also lateral movements of arms & legs),
> -centrally placed lumbar spine, with 5 rather than 7 lumbar vertebras, etc.

Could you explain the connections? none of these suggests "aquarboreal" to me.

> This locomotion has been called (google) "aquarboreal" (aqua=water, arbor=tree).

By you, yes, but here is what a search in google led to:

https://groups.io/g/AAT/message/70711

Jack, whoever he is, has trouble with the connections there. And your answers to him don't explain them.

Peter Nyikos
Professor, Dept. of Mathematics
Univ. of South Carolina -- standard disclaimer--
http://people.math.sc.edu/nyikos

Op dinsdag 21 maart 2023 om 22:12:52 UTC+1 schreef Peter Nyikos:
> Thank you for reviving this thread, Marc. I hope you are still monitoring it,
> because I have a lot of comments to make on what Daud wrote, and on some that you added,
> and I'm curious to see what you think about them.
> You might not know that Daud announced here in s.b.p. about two
> months ago that he was taking a vacation from here and also from sci.anthropology.paleo.
> So don't expect any responses from him any time soon.

OK, Peter.
DD (Daud Deden) often has a lot of interesting thoughts.

> > > The Origins of Bipedal Locomotion
> > > William EH Harcourt-Smith 2013
> > > Handbook of PA doi 10.1007/978-3-642-27800-6_48-3
> > > Bipedalism is a highly specialized and unusual form of primate locomotion that is found today only in modern humans. [DD: Sifaka, Hylobatidea, All known Homo spp.]

> This was a very valid correction by Daud. I don't know whether he includes Indris or Avahis
> under "Sifaka", but they too are bipedal. There may be something about Madagascar, where
> all 3 of these other primates originated, that encourages bipedal locomotion.

> > > The majority of extinct taxa within the Hominini [DD: Hominoidea] were [DD: arboreal] bipedal,

> Here, OTOH, Daud was introducing a separate theme and not necessarily disagreeing.
> Do you see it that way too, Marc?

The hominoid LCA was already "bipedal", but arboreality alone isn't enough to explain BPism.
Since Primates are generally arboreal, and early-Pleistocene H.erectus was (semi)aquatic (his pachy-osteo-sclerosis is exclusively seen in slow+shallow-diving tetrapods), there must have been (since evolution is gradual) an intermediate phase of trees+water = aquarboreal (aqua=water, arbor=tree). AFAIR, I proposed this in 1990 or so, and a few years later, the wading gorillas of Ndoki were discovered (& later also wading bonobos & orangutans :-)). Aquarboreality IMO best explains why apes (vs monkeys) are more vertical, have less lumbar vertebras, a more centrally-placed lumbar spine, a very broad sternum (Hominoidea=Latisternalia) & thorax, placing the scapulas more dorsally (allowing more lateral movements of the arms), lost the tail (very unexpected in fast-moving purely arboreal mammals), climbed arms overhead (in the branches above the water) etc.

> > > but the degree to which they were bipedal remains the subject of considerable debate. The significant discoveries of fossil hominin remains in the last 40 years have resulted in this debate becoming increasingly focused on how bipedal certain fossil taxa were, rather than on the overall process. Although the early hominin fossil record remains poor, evidence points to at least 2 distinct adaptive shifts. First, there was a shift to habitual [DD: arboreal] bipedalism,

> Here, too, Daud was not necessarily disagreeing; here, though, he was adding details
> to the locomotion method rather than expanding the range of taxa.

Miocene Hominoidea were very "bipedal"(aquarboreal) IMO: they spent a lot (even most?) time wading?

> > > as typified by certain members of Australopithecus, but possibly including earlier genera such as Ardipithecus and Orrorin. Such taxa were [DD: arboreal] bipedal, but also retained a number of significant adaptations to arboreal climbing. The second shift was to fully obligate bipedalism [DD: Sifaka, Hylobatidae, Homo are all obligate bipeds.] and coincides with the emergence of the genus Homo [DD: No, of course not.].

> I'm not sure, but I think the author, William EH Harcourt-Smith, was only interested in the lineage
> leading up to Homo, and may have thought that bipedalism was independently acquired by
> Hylobatidae, as it seems to in the case of the lemurs mentioned above. Or he may have thought
> that bipedalism was temporarily lost in our lineage, and then regained.

Sifakas = hopping BPism, cf. kangaroos = ex-arboreal?
But gibbons-humans = striding BPism = ex-aquarboreal?

> > > By the Early Pleistocene, certain members of Homo had acquired a postcranial skeleton indicating fully humanlike striding bipedalism [DD: No chin so they must have had a different striding gait & weight distribution than modern humans].

> I do not see how the word "must" is justified by "No chin." Do you, Marc?

No, I don't see what DD means here.
Ou chin IMO results from the (mid?late-Pleist.) transition diving->wading (cf. horizontal->vertical), cf. also less projecting mid-face, reduced nose-size, more anterior foramen magnum, higher forehead & brain-skull, loss of platycephaly, longer legs, less wide pelvis etc.

> > > The final part of this chapter reviews why bipedalism was selected for. [DD: Bipedalism long preceded the advent of Homo sapiens.]> See above about "lineage."
> > > There have been many theoretical explanations, and the most robust remain those linked to the emergence of more varied habitats. Such an environmental shift would have involved strong selection for new behavioral strategies most likely linked to the efficient procurement of food. [DD: Such as better access to arboreal fruits and nuts]

> Here is where you came in, Marc:

> > I mostly agree with DD, but IMO we should specify:
early-hominoid BPism was less walking-climbing BPism than wading-climbing BPism?
Miocene Hominoidea lived in swamp forests, esp. in coastal forests in S-Eurasia along the Tethys Ocean?

> I've known about your wading-climbing hypothesis for over a year now, Marc, but
> I don't recall anything about the location. In fact, I just had Africa in the back of my
> mind when I read what you and Daud and Mario had written about it.

My book "De evolutie van de mens" (Acad.Uitg. Eburon 2022 Utrecht NL) p.299-300:
plate tectonics & hominoid splittings: hypothesis in short, schematically:
-c 30-25 Ma India approaches S-Asia -> archipel fm = islands + coastal forests++ in Tethys Ocean:
some Catarrhini reaching these coastal forests evolved -> aquarboreal Hominoidea,
-c 20 Ma Ma India underneath Eurasia split lesser hylobatids(East) & great apes (West -> Tethys Sea),
-c 15 Ma Mesopotamian Seaway closure split pongids-sivapiths East & hominids-dryopiths West,
most died out late-Miocene, except in (incipient then) Red Sea: hominids s.s. (today Gorilla-Homo-Pan),
-c 8 Ma northern Rift fm -> Afar: Gorilla -> Praeanthropus afarensis late-Miocene -> boisei early-Pleist. etc.
-c 5 Ma Red Sea opened into Gulf (Francesca Mansfield: caused by Zanclean mega-flood 5.33 Ma):
Pan -> right -> E.Afr.coast -> southern Rift -> Transvaal: Au.africanus late-Mio-> robustus early-Pleist. (// Gorilla),
Homo -> left -> S.Asian coast -> Java -> + shellfish-diving ?early-Pleist.H..erectus = "aq.ape" s.s.: shellfish?

IOW, schematically:
Mio-Pliocene aquarboreal Hominoidea
-> early-Pleist. predom.diving H.erectus
-> mid-Pleist. diving+wading (e.g. H.neand. seasonally along rivers following salmon??)
-> late-Pleist. wading-walking H.sapiens?

> It's an interesting amplification: is it possible that our lineage goes back to SE Asia before
> moving to Africa? or should I say, back to Africa? [Recall Proconsul and Ekembo, 17 to 20 mya,
> predating Ramapithecus/Sivapithecus by about 5my.]

Yes, Out-of-Africa = empty slogan IMO: we come from S-Asia...

> > where they frequently waded bipedally (upright) in the shallow water between the trees, and often climbed arms overhead in the branches above the water. This explains best in apes:
> > -complete tail loss,
> > -very broad sternum, thorax & pelvis + dorsal scapulas (also lateral movements of arms & legs),
> > -centrally placed lumbar spine, with 5 rather than 7 lumbar vertebras, etc.

> Could you explain the connections? none of these suggests "aquarboreal" to me.

No?? Swamp?coastal forest: quadrupal->BP = upright:
-- head above the water,
-- climbing arms overhead in the branches above the water!

> > This locomotion has been called (google) "aquarboreal" (aqua=water, arbor=tree).

> By you, yes, but here is what a search in google led to:
> https://groups.io/g/AAT/message/70711
> Jack, whoever he is, has trouble with the connections there. And your answers to him don't explain them.
> Peter Nyikos Professor, Dept. of Mathematics
> Univ. of South Carolina -- standard disclaimer--
> http://people.math.sc.edu/nyikos

That's Gareth's opinion, but imagine a wading hominoid (e.g. collecting mangrove oysters??):
his tail has no function AFAICS, only drag & infection-risk?

Google "GondwanaTalks Verhaegen English" (or better: read my book...).
My hypothesis "plate tectonics = hominoid splittings" is recent, just in time for my book: appendix 16:
"Bijlage 16: "Platentektoniek en Hominoïde Opdelingen?" :-)
These are in fact different hypotheses,
- I'm pretty sure of Gorilla (Lucy in the N-Rift) // Pan (Taung in the S-Rift) and Pliocene Homo along the S-Asian coast,
- but a bit less sure about hominid/pongid = Mesopot.Seaway closure,
- and even less about India approaching S-Euasia = OWM/ape & lesser/gr.ape splits?