Re: Bipedalism in humans


alandarwinvanarsdale
 

Extant great apes can adapt well to bipedalism. If bipedalism begins before adulthood primates osteology in general is rather plastic and can adapt to different modes of locomotion. Many mistakes were made in OoA paleoanthropology about great ape locomotion, despite Leakey had the anthropology department include specialists in great apes taking them out of the zoology department. Great apes can learn to swim on their own if given access to water (only a few years ago all the greats were saying they could not because they can be contained by moats in zoos), great apes can stand on one leg with an unbent knee (again they were wrong only a few years ago). They ignored how Olliver moved, Olliver was the first great ape documented to move well bipedally, now there are many, including a few films of orangutans and Pan troglodytes moving well bipedally in the wild. ______________________________________________________________________________________________________________________________________________Bonobos became known only in my life time, and again the professionals failed to adapt to and understand how they move. Any bonobo researcher can tell you about 40% of bonobo time on the ground is as bipeds. Hylobatids rarely walk as bipeds, they run, and quite fast and up to about one mile. Pliopithecoids (basal monkeys closer to Old World monkeys but also with some New World monkey traits not seen in Old World monkeys), are the oldest known terrestrial bipedal primates. They seldom are found with Hominids, as they are from wetter environments than Hominids. They are also now known from Africa. _______________________________________________________________________________________________________________________________________________It has been proposed in the literature pliopithecoids, not hylobatids, are ancestral to Hominids. This appears quite unlikely. However, HGT from pliopithecoids into Hominids, or some sort of gene flow between pliopithecoids and some other monkey group (such as with affinities to Proconsul, though Proconsul itself was not ancestral to Hominids as was once thought), to generate Hominids as hybrids of two monkey groups. _____________________--------------------------OoA solved most of the great mysteries of human evolution, a linear progression in known fossils from Africa, killer apes, bipedalism being the first hominins as great apes driven away from the trees, gentle ape killer hominin, problem is, they were wrong about most things. In reality there is still a very lot unknown about human evolution, including the details of Hominid aquatic adaptations. Again today Hominin means closer to us than any living great ape, and Hominid is us and great apres together (in the 1960's the meanings were different). _______________________________________________________________________________________________________________________________________________Hylobatids are certainly the closest relatives to the Hominids. Hominids can even be understood as one small branch of hylobatids (which does bust OoA for the origin of Hominids until the find hylobatids in Africa). Hylobatids and Hominids are grades of some group of monkeys or combination of different groups of monkeys. Anyone who doubts Hominids can have monkey genes coming in after Hominids and hylobatids diverged from other monkeys should study baboon HGT genes in chimps from about 2 million years ago (when baboons were only in Sub-Sahara). Hylobatid bipedalism has been severely over-looked and under-studied by very ignorant OoA models for Hominin bipedalism. I doubt Hominin bipedalism is so simple as being directly derived from hylobatid bipedalism. More likely before Hominids diverged from hylobatids both groups already had well developed terrestrial bipedalism. And why not, since it is now well established terrestrial bipedalism beginning with the first Hominins is pure OoA fantasy, and we do not actually know when or where it first appeared in Hominids. 


On Thu, Apr 21, 2022 at 8:36 AM Jack D.Barnes <needininfo@...> wrote:
Bernard,
Bipdelism is the natural state of the stem great apes, (all great apes were bipedal, only homo retained it).

 Bipedalism was and is the natural result of the swinging motion of the Hylobates, which have never been in Africa.   How do they swing?  Feet raised forward, motionless, as the shoulder swing side to side. The lumbar section needed to twist, the tail is actually a disadvantage and hence was lost.  This required a new and still unique feature of the mammalian 5 section backbone, the lower lumbar twisting section.  It allows the Hylobates to travel 50kmh in the trees.

On the ground, running or walking Hylobates do the opposite…Holding arms and shoulders still while the hips swing side to side.  The biomechanics of their bodyplan allows them to do nothing else. Bipedal on the ground, legs motionless in the air. 

Humans also have the twisting lumbar section and it affects everything we do. freestyle in swimming, the golf swing, baseball pitching, all have shoulders turning independently of the hips.  

On the other hand Kicking a soccer ball, bipedal running and dancing all require the opposite, turning hips while maintaining the shoulders.   We are highly improved versions of the hylobate body plan.   

Gorilla, Orang and Chimp are quadrupeds and MUST not have a twisting section. So they have fused it in 3 creative ways.  

The only explanation is homo separated from Chimp, Gorilla and Orang while it still had the bipedal design, at least 20mya.  We share ZERO of the chimps lumbar adaptations.  We share none of the African virus load in the Miocene. 

Not a single human ancestor was in Africa between 24mya and 1.8mya.  Not one.   The great apes radiated from SE Asia as bipedal, hylobate-like creatures with a twisting lumbar section.   

-Jack


On Apr 21, 2022, at 1:52 AM, Gareth Morgan <garethmorgan@...> wrote:





From: AAT@groups.io <AAT@groups.io> on behalf of fceska_gr via groups.io <f-ceska=odysseysailing.gr@groups.io>
Sent: Wednesday, April 20, 2022 6:26 PM
To: AAT@groups.io <AAT@groups.io>
Subject: Re: [AAT] Homo erectus (sensu stricto) the most aquatically adapted hominin?
 

G: How do you determine tree climbing skills? In any case Australopiths were less aquatic than us and apparently are not considered ancestral to us anyway. This is all also predicated on the view that bipedalism is an aquatic adaptation. I don't think that was why it evolved originally.

 

F: “Many of the same features seen in australopithecines in Africa that are often cited as an indication of a species belonging to the human lineage, such as an anteriorly situated foramen magnum, short but broad ilia, relatively small canines, etc., are also found in many of the fossil apes from Europe (Wood & Harrison, 2011). Furthermore, if a taxon displays features both for bipedalism and arboreal climbing, it is traditionally understood to imply that the species is somehow transitional between a more arboreal earlier form and a later more terrestrial form, when it could just as easily have been going the other way. Evidence shows that some late australopithecines, such as Australopithecus sediba from 1.98 Ma, were more arboreal than earlier australopithecines, such as Australopithecus afarensis (Rein, et al., 2017*). The same could be said regarding brain sizes as we quite often see that the later australopithecines had smaller cranial capacities than earlier fossils. For example, from East Africa, the younger Paranthropus aethiopicus (2.7-2.3 Ma) had a cranium (c. 410 cc) falling within the range of the much older A. afarensis (c. 375-550 cc) at 3.9-2.9 Ma; while in South Africa, at 1. 98 Ma, A. sediba’s cranium was 420-450 cc and therefore smaller than A. prometheus’s cranium (500-520 cc) was already at 3.67 Ma. Although we are not claiming a direct line through any of these species, there is no clear trend showing that australopithecines were becoming more Homo-like over time.”

“Researchers compared A. prometheus’s shoulder to apes, hominins and humans and found that Little Foot was adapted to living partially in the trees and partially on the ground. As well as relatively long legs and limited bipedal foot morphology, it had a long, curved clavicle and dorsally positioned scapula with a high ridge to attach heavy muscles, ideal for supporting its weight below branch, more similar to that seen in arboreal apes, such as chimpanzees. They concluded that “the arm of our ancestors at 3.67 Ma was still (my emphasis) being used to bear substantial weight during arboreal movements in trees, for climbing or hanging beneath branches.” [i] The assumption here is that this is a retained feature from a more primitive ancestor, rather than the expression of an earlier adaptation as a result of returning to the trees.”

“In a recent paper, scientists revealed the results of a study in which they compared the heel bones (calcanei) of humans, extant apes and various hominin fossils. They found that earlier Australopithecus species, such as Lucy’s, had a heelbone more similar to humans than apes, better to support their weight on two legs, while later apiths had more ape-like heelbones, suggesting a reversal over time from bipedalism to arborealism.[ii] Other researchers studying hominin foot evolution have suggested that the similarities between A.afarensis’ feet and human feet might imply that they both “descend from a common ancestor with a similarly derived foot” and that “the large calcaneal tuber (heel bone) is obtained in developmentally different ways in A. afarensis and in modern humans.”[iii] In other words, homoplasy.

 

*Adaptation to suspensory locomotion in Australopithecus sediba

https://www.sciencedirect.com/science/article/abs/pii/S0047248416302743

 

(I’m not claiming bipedalism is strictly aquatic, although I do think it emerged out of orthograde apes wading in wetlands in the first instance. And I don’t believe australopithecines are ancestral to us, but ancestral to the African apes, which is the point I’m making here).

 

There is evidence that Pan’s feet were once like ours

 

G: I have been looking long and hard and found nothing. This is quite important. I won't take it on trust. All the evidence (in utero, for instance) that I can find says the opposite.

 

F: Marc has always referenced C. S. Coon for this, but I haven’t been able to find the direct source. However, in another paper I found this (with no reference).

 

“The marked abductability of the chimpanzee hallux is probably a derived condition within the human/African ape clade. Indeed, embryos of chimpanzees have an adducted hallux suggesting that relative adduction could be the LCA primitive condition…”
Meldrum, Jeff & Sarmiento, Esteban. (2018). Comments on possible Miocene hominin footprints. Proceedings of the Geologists' Association. 129. 10.1016/j.pgeola.2018.05.006.

 

Also, Schultz, 1925 noted – although he doesn’t say at what stage this happens in chimpanzees…


“In all primates the great toe is found to branch from the sole, just at the base of the second toe, in very early growth stages. This embryonic position is retained throughout life in man, whereas in all other primates the place of attachment of the great toe shifts proximally, similar to the ontogenetic shifting in the attachment of the thumb to the palm from the base of the index finger to a place nearer the wrist. In the gorilla this shifting of the hallux is least pronounced of any of the apes, whereas it is most extreme in the orang, a greater difference existing in this respect between the latter and gorilla than between gorilla and man (fig. 16). Other propor tions on the foot lead to similar conclusions…”

https://www.jstor.org/stable/pdf/24527371.pdf

 

G: If there have been no reversals, then in what possible sense can we be less aquatic than we used to be?

 

F: There are many ways. Read the paragraph I wrote further down about ‘reduction’ of features (smaller lungs, etc.), and this is only from fossil evidence, which is very limited, and based on comparative anatomy with other species, so we can’t really know what other features we may have fully lost. Maybe we did have webbing between our fingers & toes… (!!)

 

I’m talking about Pan (chimps) not Homo.

 

G: The premise I thought we were discussing was the one about whether early Homo was more or less aquatic than us. Whether chimps reverted or not really doesn't have any bearing.

 

F: Yes, we were, but earlier we were also talking about climate and how it instigated evolutionary changes. I included a small two-line reference to Panins to suggest why the australopithecines may have become more arboreal as the African wetlands dried up.

 

Thick brow ridges are great if you dive, browse and forage underwater... to push water away from the eyes

G: This is simply not true. I've mentioned katabatic flow to you before. When any fluid flows over a ridge it drives forcibly down the other side. Into your eyes in other words if it is a brow ridge.

 

F: I’m not convinced by this but clearly more research is needed. I suppose it is testable. The example you give is based on air, not water, and presumes a straight directional flow over the ridge. I believe the brows on a hominin, face down in water, would divert the flow of water away to the sides of the face. Maybe it’s not so much to do with swimming but even surfacing regularly to breathe. With a flat face and no brows the water would just pour straight down into your gasping mouth. In general, our brows are thought to be useful in diverting sweat from flowing into our eyes, so the same principle is true, but just with more water, more regularly.

 

And how do you get “more aquatic” Asian people? Some are, of course, if you’re thinking of Moken, etc. or Japanese pearl divers, but can we say Asians are more aquatic. We are all still H.sapiens.

 

Neanderthals were more aquatic than Homo sapiens. 

 

G: A bigger brain, I happily concede. However all the known big headed humanoids became extinct -- proto-Innuit, Boskop man, "coneheads", Neanderthals.... The fact that fewer and fewer females appeared over time suggests that heads became too big to pass through the birth canal, killing the mothers in childbirth. We are about on the sustainable limit, partly thanks to Caesarian sections. A reality that anthropologists manage to ignore, preferring to focus on how jolly intelligent they think they are.

 

F: Is that a fact? Do you have a reference? We don’t know why Neanderthals went extinct. Many reasons are proposed.

 

G: Homo erectus had a tiny brain anyway. Are we to conclude then that he was less aquatic than us? Makes sense. We just can't have it both ways.

 

F: Homo erectus’ brain capacity, with an average of 950cc, [iv] ranged from 550cc in some early samples, to 1251 cc,[v] which is close to that found in modern humans. (I personally believe that brain size increase is a result of marine-chain based nutrients + cold water, which explains the size increase as the climate got cooler. Neanderthals with the largest brains, swam in the cold waters of the Atlantic. Only a more aquatic species would do that regularly, don’t you think?).

 

G: Big, heavy bones are really a huge handicap in the water if you think about it. Bad for swimming and floating. Good, on the way down, for diving. Coming up...  good for drowning. Manageable in sea water. Big problem in fresh. Neanderthal was robust because, like Australopithecus robustus, he was designed to live mostly on land and struggled to make a living in the water, not yet having our perfect neutral buoyancy and other modern refinements. Frequently fractured his skull diving in, apparently.

 

F: “In the animal kingdom, good runners tend to be gracile, or lightly built, (e.g., cheetahs, antelopes, horses, greyhounds), and even floating semi-aquatic animals such as ducks have light bones. Conversely, dense, heavy bones tend to be brittle and not suitable for fast or sustained terrestrial locomotion. As noted by Alexandra Houssaye, et al, in their study of amniote bone microanatomy regarding thick cortical bones: “These rather well-known specializations are considered incompatible with a terrestrial locomotion and generally do not occur (or incipiently so) in terrestrial taxa… or even in most semi-aquatic taxa.” In contrast, bone mass increase is found “in almost all highly or exclusively aquatic amniotes foraging below the water surface.[vi]

 

Seems quite clear to me that both erectus and Neanderthals, with their heavier, more robust bones, were better suited to shallow diving and totally incompatible with running. And possibly why women have more fat then men (males may have been deeper divers) and why women gain fat & lose bone density after menopause when they have to be floating around at the surface with the grandkids.

 

G: As you know I consider the most aquatic hominin ever was Strandlooper (Boskop man) -- extinct for only a few hundred years or so. If you look at all the (aquatic) features that distinguish us from earlier ancestors, Strandlooper had them all, but very much more so. We know they were fully dependent on marine resources, because to find even a blade of grass they would have had to cross both the Kalahari and the Namib deserts, the latter having existed for over 50 million years, and you can see their shell middens from many miles away.. 

 

They were more gracile than us. "paper thin ribs" Their brains were a full 30% bigger than ours (forebrains + 50%). No brow ridge at all. Tiny teeth. Very prominent, sharp chin. Different in every way from the rugged Neanderthals. More aquatic....

 

F: I can’t comment on Strandloopers – I haven’t researched them yet. It sounds as though there are a mix of features. If they had gracile bones, they may have been surface swimmers rather than divers.

 

 just because we evolved a certain feature, it doesn’t mean we will lose it once we stop needing it. 

 

G: Precisely, then we obviously have more aquatic adaptations than any previous hominin who hadn't yet developed them. i.e we are the most aquatic (surviving) hominin.

 

F: Not losing a feature doesn’t mean it still serves its original function, especially if it is reduced. I repeat: we have smaller lungs, longer legs, lighter bones & shorter femora (better adapted to terrestrial locomotion than our ancestors), more globular crania, lower eyes, flatter faces (better when standing erect), smaller brains (less swimming in cold water, less seafood consumption, self-domestication-agriculture), we are probably less fat than Neanderthals (although they weren’t direct ancestors, we seem to have inherited our fat genes from them). Also, we cannot say that modern Homo sapiens – as a whole – is predominantly aquatic anymore. We retain some reduced aquatic features and tendencies. The whole point of the “Scars of Evolution” (E. Morgan) is that our scars are the remnants of a more aquatic past. Hardy and Morgan had it right. We were more aquatic in the past, but we can agree to disagree as everyone does here! 😊

 

QED.

 

 

From: AAT@groups.io <AAT@groups.io> On Behalf Of Gareth Morgan
Sent: Tuesday, April 19, 2022 10:54 PM
To: AAT@groups.io
Subject: Re: [AAT] Homo erectus (sensu stricto) the most aquatically adapted hominin?

 

The climate I refer to from Miocene onwards is all supported by scientific research.

 

Yes. It's only the older stuff I decline to offer any opinions on.

 

 

There are quite a few scientists who now support that knuckle-walking developed in Pan and Gorilla in parallel  

 

I have no problem with that.

 

 

 

 Australopithecus sediba, a very late surviving hominin, was clearly smaller and more arboreal than Lucy was 3.4 Ma.

 

Smaller, maybe. How do you determine tree climbing skills? In any case Australopiths were less aquatic than us and apparently are not considered ancestral to us anyway. This is all also predicated on the view that bipedalism is an aquatic adaptation. I don't think that was why it evolved originally.

 

There is evidence that Pan’s feet were once like ours

 

I have been looking long and hard and found nothing. This is quite important. I won't take it on trust. All the evidence (in utero, for instance) that I can find says the opposite.

 

 

 

I think you misunderstood me… there was only one reversal

 

Great. If there have been no reversals, then in what possible sense can we be less aquatic than we used to be?

 

 

I’m talking about Pan (chimps) not Homo.

 

The premise I thought we were discussing was the one about whether early Homo was more or less aquatic than us. Whether chimps reverted or not really doesn't have any bearing.

 

 

 

Thick brow ridges are great if you dive, browse and forage underwater... to push water away from the eyes

 

This is simply not true. I've mentioned katabatic flow to you before. When any fluid flows over a ridge it drives forcibly down the other side. Into your eyes in other words if it is a brow ridge. Here's a diagram of a "Chinook wind" to illustrate what happens.

 

image001.png

 

"A 40- to 50-mph wind over the ridges and passes may reach speeds of 80 to 100 mph by the time the air reaches the foothills (on the other side)".



It therefore follows that losing the brow ridge makes for better underwater vision. The more aquatic Asian people have less of a brow ridge than westerners and modern Man has a more "streamlined" face than any previous ancestor. i.e. more aquatic.







Neanderthals were more aquatic than Homo sapiens. 

 

A bigger brain, I happily concede. However all the known big headed humanoids became extinct -- proto-Innuit, Boskop man, "coneheads", Neanderthals.... The fact that fewer and fewer females appeared over time suggests that heads became too big to pass through the birth canal, killing the mothers in childbirth. We are about on the sustainable limit, partly thanks to Caesarian sections. A reality that anthropologists manage to ignore, preferring to focus on how jolly intelligent they think they are.

 

Homo erectus had a tiny brain anyway. Are we to conclude then that he was less aquatic than us? Makes sense. We just can't have it both ways.

 

Big, heavy bones are really a huge handicap in the water if you think about it. Bad for swimming and floating. Good, on the way down, for diving. Coming up...  good for drowning. Manageable in sea water. Big problem in fresh. Neanderthal was robust because, like Australopithecus robustus, he was designed to live mostly on land and struggled to make a living in the water, not yet having our perfect neutral buoyancy and other modern refinements. Frequently fractured his skull diving in, apparently.

 

 

As you know I consider the most aquatic hominin ever was Strandlooper (Boskop man) -- extinct for only a few hundred years or so. If you look at all the (aquatic) features that distinguish us from earlier ancestors, Strandlooper had them all, but very much more so. We know they were fully dependent on marine resources, because to find even a blade of grass they would have had to cross both the Kalahari and the Namib deserts, the latter having existed for over 50 million years, and you can see their shell middens from many miles away.. 

 

They were more gracile than us. "paper thin ribs" Their brains were a full 30% bigger than ours (forebrains + 50%). No brow ridge at all. Tiny teeth. Very prominent, sharp chin. Different in every way from the rugged Neanderthals. More aquatic....

 

 

 just because we evolved a certain feature, it doesn’t mean we will lose it once we stop needing it. 

 

 

Precisely, then we obviously have more aquatic adaptations than any previous hominin who hadn't yet developed them. i.e we are the most aquatic (surviving) hominin.

 

QED.

 

G.

 


From: AAT@groups.io <AAT@groups.io> on behalf of fceska_gr via groups.io <f-ceska@...>
Sent: Tuesday, April 19, 2022 7:02 PM
To: AAT@groups.io <AAT@groups.io>
Subject: Re: [AAT] Homo erectus (sensu stricto) the most aquatically adapted hominin?

 

Thanks, Gareth

Thanks, Francesca.

 

Would it be possible to reveal the source of this text

 

That would be me.  Email, subject "Second draft" about where when and how we became aquatic.

Ok, thanks. I’ll have another look for it.

 

 many of our “aquatic” adaptations stretch back at least as far as the early Miocene and most of the changes seem to be instigated by climatic changes.  

 

Agreed. But they didn't spring up, fully formed overnight. They gradually improved, gradually increased in number and range of functions.

Agreed, that’s what I’ve been writing about.

 

I'm not making any guesses about what happened before the Miocene --  what the climate was like in some particular region, tectonic events, sea levels, vegetation, predators or the particular 'cause' of any specific change in physiology. For one thing I'm sure that none of these conditions remained unchanged for millions of years at any point, so too much of it is guesswork based on insufficient evidence. Almost anything could have happened somewhere at some point.

The climate I refer to from Miocene onwards is all supported by scientific research.

 

reversal from upright bipedalism towards arborealism

 

Not aware of any evidence for this "reversal". Not to say it couldn't or didn't happen, but if I ever knew of any evidence, I've forgotten.

There are quite a few scientists who now support that knuckle-walking developed in Pan and Gorilla in parallel, from an already upright common ancestor, after splitting from a common ancestor. First they walked on 4 legs, then they walked on 2, then they walked on their knuckles.

Many of the australopithecines seem to become more arboreal over time, not less. Eg. Australopithecus sediba, a very late surviving hominin, was clearly smaller and more arboreal than Lucy was 3.4 Ma.

 

My only comments would be that, once we learned to throw, we were never able to brachiate again because of the change in orientation of our pectoral muscle.. Once we became bipedal, the loss of the divergent hallux meant we could never grasp a branch with our feet again. Not sure what kind of arborealism this would leave us. 

Humans didn’t become arboreal again, only Pan did. The point I’m trying to make is that the LCA was probably already a biped. After we split, the Pan line remained bipedal (wading, wetland foraging) for a while, but later, they returned to the forests, started climbing trees and walking on their knuckles when on the ground. There is evidence that Pan’s feet were once like ours (adducted halluces) but later their big toe moved round to the side and they could grasp branches again. (Pan foetus in utero).

 

 I don’t believe sapiens are the most aquatic. I think early Homo was more aquatic than we are now.

 

We need to look at the other features that you consider reversals to see if any of them are aquatic features that we have lost since early Homo....

I think you misunderstood me… there was only one reversal I mentioned and that was in chimps…

 

You mention...

 

6 Ma: human-like foot morphology (loss of arborealism). -- Arborealism is definitely not aquatic.

That’s my point. We lost arboreal features because we became more aquatic. Or, because we became more aquatic, we lost arboreal climbing abilities.

 

5-2 Ma: Gradual reversal from upright bipedalism. -- Don't think I believe this (Open to persuasion. See above.) but anyway bipedalism is either not essentially aquatic, in which case it's irrelevant or it is, in which case we have become more aquatic (more upright), not less, since early Homo.

Yes, again, I think you’ve misunderstood me. Here I’m talking about Pan (chimps) not Homo. Reverse adaptations in evolution are more common even than first time adaptations. It happens all the time. It’s a result of gene expression. Once the gene exists, it can be switched on or off, according to need. That’s why snakes evolved legs, then lost them again. So did whales, etc. Chimp and human ancestors lost their fur, then chimps grew theirs again, but we didn’t. Early elephants lost their fur but woolly mammoths grew it back as they moved north. Some people are sometimes born with a tail, or webbing between their toes, because those genes still exist, even if silenced at the moment.

 

I think Homo is closer to the LCA in morphology than chimps. We haven’t changed as much as they have over the past 5-6 million years, and this is seen in their Y-chromosome. And most of those changes in chimps probably happened in the last million years or so, after they diverged from bonobos. Bonobos are more like us than chimps are (see picture attached).

 

2.0 Ma: Homo appears:  taller, larger with longer legs, increased thoracic capacity, heavier leg bones, heavier crania, larger brain (significant development of cortex associated with vision and manual dexterity), improved dexterity, platycephaly, hooded nose, thick brow ridges, improved shoulder rotation, no evidence of sexual dimorphism, more sophisticated stone tool use, shellfish consumption. -- Other than the thick brow ridges (survival benefit not obvious to me) these all seem to be increases in aquatic adaptation.

Thick brow ridges are great if you dive, browse and forage underwater. Like a hooded nose, they act together to push water away from the eyes and nostrils as you move forward.
And yes, this is meant to demonstrate increases in aquatic adaptation. My point is, early Homo at 2 Ma was far more aquatic morphologically than H. sapiens is now.

 

300 ka to present: Ear exostoses, larger brains, heavy bones, multiple crania fractures, larger eyes (cold-water diving?) -- Again these seem to be evidence of a more aquatic lifestyle, not less.

Yes, Neanderthals were more aquatic than Homo sapiens. Again, that’s my point.

 

Which aquatic features do you think we have lost, then? What makes you think we are less well adapted to warm, cold, shallow, deep, clean, muddy, fresh or salt water than any of the less derived hominins? Your entire timeline seems perfectly to support my observation that aquatic adaptations have been a gradual, punctuated, cumulative process that has continued till today.

We haven’t fully lost any of those earlier adaptations (that we know of) but each is less pronounced. We have smaller thoraxes and reduced lung capacity compared to early Homo, as we don’t dive as much. We have lighter bones because we walk/run more, swim and dive less. We can’t see well underwater unless this skill is practised from childhood. We have less pronounced brow ridges for the same reason. We have rounder crania as we spend more time standing upright, whereas the more elongated crania of early Homo is better supported in a swimming, floating or diving position. We can swim and dive pretty well, for an ape, but not as well as erectus probably did. They may have been able to swim vast distances and dive to much deeper levels. They could probably hold their breath much longer than we can, or close to what professional / record holding divers can do now.

 

As your mum once wrote, just because we evolved a certain feature, it doesn’t mean we will lose it once we stop needing it. We would only lose it if keeping it was detrimental to our survival. We haven’t regrown our fur because we discovered clothes and central heating as an alternative means of keeping warm (and still get to go to the beach!) If we hadn’t, only the most hairy of us would survive in a colder climate to pass on our genes, so over time, our children would get hairier and hairier. We didn’t revert to quadrupedalism because by the time we became fully terrestrial again, our legs were much longer in relation to our arms and so the proportions were all wrong. Plus, we didn’t need to. By then we were quite comfortable moving around on 2 legs and using our forelimbs for other purposes. It’s served us quite well.

 

F.

G.

 

 


From: AAT@groups.io <AAT@groups.io> on behalf of fceska_gr via groups.io <f-ceska@...>
Sent: Tuesday, April 19, 2022 12:19 PM
To: AAT@groups.io <AAT@groups.io>
Subject: Re: [AAT] Homo erectus (sensu stricto) the most aquatically adapted hominin?

 

Hi Gareth,

 

Would it be possible to reveal the source of this text, please? I’d like to read it.

 

I agree that climate has influenced anthropoid evolution at many stages and in different ways, although I don’t believe sapiens are the most aquatic. I think early Homo was more aquatic than we are now.

 

If we look at the evidence, many of our “aquatic” adaptations stretch back at least as far as the early Miocene and most of the changes seem to be instigated by climatic changes.  

 

[1st aquatic stage: Hominoidea]

30-25 Ma Climate: very hot, humid, subtropical forests; tectonic upheaval and rifting causing vast areas of East Africa to become flooded, creating forested islands in vast East African lakes.

25-20 Ma: orthograde body plan and modifications towards bipedal posture, suspensory adaptations of the wrist, hand, shoulders and arms, larger, wider thorax, loss of tail, etc.
20 – 14 Ma: gradual increase in size from small-bodied primates to large chimp sized apes

Some time between 25 Ma and 16 Ma: partial loss of pelage (great apes relative to macaques)

Overall increase in eccrine gland distribution (between OWMs and apes)

Probable reduction in olfactory ability

PNS

c. 18- 16 Ma Hylobatidae diverge

 

16-14 Ma: Climate: temperature decrease, reduced humidity & loss of biodiversity in Africa; increasing biodiversity, humid sub-tropical forests & vast bodies of water in Eurasia, land bridges between the two continents. Disappearance of most apes from Africa. Appearance of many ape species in Eurasia.

15 Ma: loss of uricase mutation and the ability to store sugars as fat

 

[Hominidae]

15-13 Ma: the ability to fashion stone tools

c. 15-14 Ma: Pongo diverges

14 Ma: plantigrade locomotion (quadrupedal)

12-11 Ma: loss of prognathism, robust jaws, postural bipedalism (wading)

11-9 Ma: Vallesian crisis causes the extinction of many apes (loss of forests, loss of edible fruits, spreading grasslands, seasonal food availability).

10-7 Ma: bipedal hominids roam the river valleys & great lakes of southern Europe & the Tethys-Med coasts.
Smaller, more thickly enamelled dentition – change of diet.

 

[Homininae]

10-6 Ma: terrestrial bipedalism develops

c. 10-8 Ma: gorilla divergence

7 Ma: human-like P4 dental root morphology

6 Ma: human-like foot morphology (loss of arborealism)

 

6-5 Ma: Pan / Homo diverge

5.9 – 5.3 Ma: Mediterranean Salinity Crisis: great unidirectional migrations of fauna away from the southern Med, towards Africa.

5.3 Ma: Zanclean Megaflood cuts off land bridge between Eurasia and Africa.

Pliocene: 5.3 – 2.6 Ma. Sea-levels rise by up to 30 m. Hyper aridity in the Arabian Peninsula prevents migration of fauna eastwards.

During much of this period, the Arabian Peninsula is effectively cut off from the rest of the world.

 

4-3 Ma (PTERV1 virus throughout Africa, affects all African apes, but not Homo or Orangutans)

 

[Panini / Australopithecines]

Climate: Loss of forests and wetlands, increase of savannah and mosaic environments

5-2 Ma: Gradual reversal from upright bipedalism towards arborealism, and eventually, knucklewalking (also in Gorilla – homoplasy).

 

[Early Homo]

2.6 – 2.0 Ma: Pleistocene cooling, sea-level decrease, vast intercontinental shelves appear, land bridges, intertidal zones, migration routes

2.0 Ma: Homo appears: taller, larger with longer legs, increased thoracic capacity, heavier leg bones, heavier crania, larger brain (significant development of cortex associated with vision and manual dexterity), improved dexterity, platycephaly, hooded nose, thick brow ridges, improved shoulder rotation, no evidence of sexual dimorphism
More sophisticated stone tool use, shellfish consumption.

 

[Later Homo]

2.6 Ma – 2.0 Ka: Pleistocene cooling, sea-level decrease, fluctuating temperatures (between glacials).

Ear exostoses, larger brains, heavy bones, multiple crania fractures, larger eyes (cold-water diving?)

 

[Homo sapiens]

300 Ka – present: Holocene (relatively stable climate, less overall humidity)

More gracile forms (taller, thinner – like waders), rounder crania, shorter femoral necks (adaptation for running). Loss of platycephaly, heavy brow-ridges, elongated crania. Brain capacity reduction, flatter faces, smaller teeth, smaller noses, lighter bones, smaller thoracic capacity,

Suggests H. sapiens was more terrestrial than earlier Homo.

 

Present – future? Anthropocene: Global warming, global climate fluctuations, sea-level rise, mass extinction events…where next?

 

Francesca

 

From: AAT@groups.io <AAT@groups.io> On Behalf Of Gareth Morgan
Sent: Monday, April 18, 2022 10:57 AM
To: AAT@groups.io
Subject: Re: [AAT] Homo erectus (sensu stricto) the most aquatically adapted hominin?

 

Homo sapiens is, if anything, more aquatic than Homo erectus.

 

 

"As far back as 17 March 1960, Professor Sir Alister Hardy noted in The New Scientist that modern humans have many features that suggest an aquatic phase in our evolution at some time in the distant past.  

The assumption was that a group of primates became isolated on an island or some other inaccessible waterside environment and survived by becoming adapted to a semi-aquatic lifestyle in the course of that single evolutionary event. Subsequent discoveries have provided data that both support and contradict that hypothesis. 

The present investigation proposes an alternative model whereby, over millions of years, a series of emergencies, in the shape of climate fluctuations, from fertile to desert conditions and coinciding with glacial and interglacial epochs, repeatedly imposed very stringent survival pressures on every group of hominids. From the late Miocene onward, scores of such events dictated the selection criteria for gradual adaptation to an opportunistic aquatic diet in a punctuated series of evolutionary steps. 

These adaptations were cumulative, and the fossil record includes progressively more numerous examples of each new version of pre-human and human with the passage of time, progressively larger deposits of bivalve shells and other edible aquatic food species in shell middens, and more widely distributed locations for the stone tools needed to process them efficiently. 

This interpretation of the available evidence satisfies all the significant objections to Hardy’s theory and leads to the conclusion that, physiologically, we are more aquatic now than we have ever been, and the astonishing current world records for breath holding and free diving would seem to support that view."

 

The idea of a single, brief isolation event producing all (or any) of our aquatic adaptations was never really credible.

G.   

 


From: AAT@groups.io <AAT@groups.io> on behalf of algiskuliukas <algis@...>
Sent: Monday, April 18, 2022 10:07 AM
To: AAT@groups.io <AAT@groups.io>
Subject: [AAT] Homo erectus (sensu stricto) the most aquatically adapted hominin?

 

For those of us who are open minded enough to answer Hardy's question "Was Man More Aquatic in the Past?" with a cautious affirmative, a second question follows "If, so when was that and how much?"

Having thought about this for twenty-five years and studied human evolution (MSc from UCL with distinction and PhD in human bipedal origins from UWA) I have come to the conclusion that the answer to the second question should be "very early modern Homo sapiens ca 200,000 years ago or so"... and... "not much".

Some proponents (e.g. Marc Verhaegen and Stephen Munro) would argue that a better answer would be "Homo erectus (sensu stricto) - i.e. the Asian, rather than African forms" and "that they were predominantly bottom divers."

That's quite a difference.

So, I'd like to discuss this openly to see if I have missed something. 

Let me start the ball rolling...

Marc always cites pacheostosis (heavy bones) of H. erectus as leaving "no other possibility" than bottom diving for this hominin but were their bones really that heavy? If you look at the Nariokotome boy femur, for example, it is remarkably gracile. Where are the papers in the literature that backs up this claim?

Marc also cites their pelvic shape as being platypelloid, with long femoral necks as further evidence but, again, that's not what I see in the literature. Nariokotome boy's pelvis is remarkably narrow actually, android rather than platypelloid. In any case what his platypelloidy got to do with bottom diving? Dugongs/manatees do not share this convergence. Their pelves, appear to be on their way to becoming vestigial like cetacea.

Whether they had heavy bones or not, there is undeniable evidence of significant weight bearing in the bones of Homo erectus. The tibial plate, the oval shaped distal femoral condyles, the robust femoral head, the large acetabulae with superiorly orientated lunate surface. The robust sacral body and large lumbar vertebrae all speak of an upright, walking, terrestrial striding biped - just like us. They seem to have been predominantly striding bipeds, not divers.

Please don't misunderstand me. I am not suggesting that Homo erectus did not swim or dive - just that they didn't do so very much, and specifically, not as much as we modern human did, or still do.

When Homo erectus reached the islands of Java and Flores some 1.8 million years ago, they could have done so without getting their feet wet as the current archipelago of Indonesia has been connected via land bridges from time to time. Of course, I have no doubt they often went swimming and diving in coastal shallows but, if they were as adept as Marc suggests (a predominantly bottom diver, remember) then it is remarkable that the narrow strait of water between Bali and Lombok across the Wallace line, just 20km wide, was never crossed by these diving hominins in 1.8 million years. If they did cross, they would have certainly populated the whole of the Australasian continent as that too was all joined by land at various times since. And yet we so no evidence of any human like species in Australia until 60,000 ago or so.

I must remind that modern humans regularly swim across such stretches of open water. The Perth - Rottnest swim is run every year and has thousands of participants. (https://en.wikipedia.org/wiki/Rottnest_Channel_Swim#:~:text=The%20distance%20is%2019.7%20km,teams%20of%20two%20or%20four.) It is about the same distance as Bali - Lombok via Penida. And of course far greater distances have been crossed than that, such as the Channel between England and France.

Of course, absence of evidence is not evidence of absence but, it seems to me that if we are to remain true to scientific principles we must base our ideas on evidence and here, the evidence is that Homo sapiens is, if anything, more aquatic than Homo erectus.

Algis Kuliukas
Perth
April 2022



[i] Carlson, K., et al.: The pectoral girdle of StW 573 ("Little Foot") and its implications for shoulder evolution in the Hominina. cs 2021 JHE in press. https://doi.org/10.1016/j.jhevol.2021.102983

[ii] Christine M. Harper, Christopher B. Ruff, Adam D. Sylvester, Calcaneal shape variation in humans, nonhuman primates, and early hominins, Journal of Human Evolution, Volume 159, 2021, 103050,

ISSN 0047-2484, https://doi.org/10.1016/j.jhevol.2021.103050. (https://www.sciencedirect.com/science/article/pii/S0047248421001020)

[iii] DeSilva, J, McNutt, E, Benoit, J, Zipfel, B. One small step: A review of Plio-Pleistocene hominin foot evolution. Am J Phys Anthropol. 2019; 168:S67: 63– 140. https://doi.org/10.1002/ajpa.23750

[iv] Rightmire GP. Homo erectus and Middle Pleistocene hominins: brain size, skull form, and species recognition. J Hum Evol. 2013 Sep;65(3):223-52. doi: 10.1016/j.jhevol.2013.04.008. Epub 2013 Jul 10. PMID: 23850294.

[v] Antón, S. C.; Taboada, H. G.; et al. (2016). "Morphological variation in Homo erectus and the origins of developmental plasticity". Philosophical Transactions of the Royal Society B. 371 (1698): 20150236. doi:10.1098/rstb.2015.0236. PMC 4920293. PMID 27298467.

[vi] Alexandra Houssaye, P. Martin Sander, Nicole Klein, Adaptive Patterns in Aquatic Amniote Bone Microanatomy—More Complex than Previously Thought, Integrative and Comparative Biology, Volume 56, Issue 6, December 2016, Pages 1349–1369, https://doi.org/10.1093/icb/icw120


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