Yep. The claim that man lived in the water for a long period of time.
That's not "the claim".
Note how diligently and persistently the people objecting to this hypothesis put up strawmen, weak versions, etc. That's not how it's supposed to be done, eh?
What about walking on two legs? That’s something all apes do a bit of – while wading in water, certainly, but also while reaching for fruit, performing aggressive displays or simply moving around in trees.
And lizards, mice, and elephants.
So?
None of that explains the radical alteration in form found in humans. The opposite - careful attention to such events reveals the high barrier that the hominid lineage overcame. Quadrupeds - including the apes - are seriously handicapped when bipedal, much clumsier and slower, much less efficient. (Except when wading, btw). The Darwinian pressure must have been something quite a bit more serious than reaching for fruit on occasion, or walking a tree limb now and then.
All the suggested anatomical and physiological adaptations [ascribed to the aquatic ape theory] can be explained by other hypotheses, which fit much better with
what we actually know about the ecology of ancient hominins.
1) We aren't talking about the ecology of ancient hominins. We're talking about the ecology of a tree dwelling quadrupedal ape.
2) That seems to be a false claim - except for, possibly, the hairlessness, which actually does have a couple of solid alternative explanations (and the big brain, which is wrong in theory and on the evidence both). Instead, we get things like this:
Sexual selection may also explain our body fat distribution, which differs between the sexes. Voluntary breath control is more likely to be related to speech than to diving.
crude errors of sequence of the kind best handled in introductory biology classes,
and this
If we evolved from ancestors who already stood up in trees, we don’t need an extraordinary explanation for why we ended up standing on the ground rather than
running around on all fours.
Uh, hello? Yes, we sure as hell do. Extraordinary occurrences require at least sufficient explanations.
How would standing up in trees - something every tree climbing organism above a certain size does on occasion, afaik - make a quadruped's choosing to handicap itself with a lifetime of clumsy, slow, inefficient, exhausting, short-legged, crippled-up, predator-attracting, ground locomotion any more likely? Bears stand on their hind legs a lot already on the ground - even in trees, when they are cubs - but not when they want to get somewhere. Likewise chimps and baboons and baby gorillas.
The original idea, and certainly Elaine Morgan’s elaboration of it, became an
umbrella hypothesis or a “Theory of Everything”; both far too extravagant and too simple an explanation. It attempts to provide a single rationale for a huge range of adaptations - which we know arose at different times in the course of human evolution. Traits such as
habitual bipedalism,
big brains and language didn’t all appear at once – instead, their emergence is spread over millions of years. It’s nonsense to lump them all together as if they require a single explanation.
This is actually a strawman. Choosing somebody's overreach or error to set up as the target of criticism, is invalid argument against the hypothesis itself.
Biologists who objected to the amphibious ape hypothesis itself, in good faith, would object to the strongest versions they could set up rather than the weakest they could find. And they would apply equivalent standards to other hypotheses competing for plausibility. Neither of those expected features of reasonable discussion appears to be common.
