Re: Homo erectus (sensu stricto) the most aquatically adapted hominin?
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.
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.
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.
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.
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.
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....
6 Ma: human-like foot morphology (loss of arborealism). -- Arborealism is definitely not aquatic.
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.
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.
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.
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.
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?
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.
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
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
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.
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).
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
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?)
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?
From: AAT@groups.io <AAT@groups.io>
On Behalf Of Gareth Morgan
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.
AAT@groups.io <AAT@groups.io> on behalf of algiskuliukas <algis@...>
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?"
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?
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
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