Thank you for commenting.

The 3 arguments you have put forward are
1) Oreopithecus bambolii’s relationship to humans and bipedalism
2) Kidney physiology of marine mammals
3) A video of chimps wading bipedally in water narrated by David Attenborough

In response:

1) As I state in the article, Oreopithecus would be nice as supporting evidence but doesn’t tell us much on its own. It is unsurprising that some similarities can be found between it and some of its distant hominin relatives – can you, however, provide a quantitative analysis of these differences? Also, as far as we know, Oreopithecus evolved in isolation on an island in Italy, not as part of the human lineage.

In a PNAS paper by Köhler and Moya-Sola, the authors conclude:

“The morphology of Oreopithecus is not ape-like, because it is functionally designed for habitual and not facultative terrestrial bipedal activities, but neither is it hominid-like, as the special environmental conditions of islands engraved their peculiar traits. Nevertheless, the striking convergences with and differences from hominids clearly make Oreopithecus a key species for understanding human bipedality. ”
http://www.pnas.org/content/94/21/11747.full
Köhler & Moyà-Solà PNAS October 14, 1997 vol. 94 no. 21 11747-11750

2) This argument only makes sense if the hominin lineage went through a fully marine, rather than freshwater or wading, phase. The modern version of the Aquatic Ape Hypothesis generally rests on freshwater wading.

3) The video you give of freshwater wading is nice but merely presents a plausible hypothesis. “Chimpanzees can wade bipedally in water” is not direct evidence for “hominin ancestors had to wade bipedally in water for much of their life”.

The two references you gave are from non-peer reviewed journals. To quote Wikipedia http://en.wikipedia.org/wiki/Medical_Hypotheses:
“Medical Hypotheses is a medical journal published by Elsevier that is intended to provide a forum for unconventional ideas without the traditional filter of scientific peer review. According to the journal’s website, it publishes “radical ideas, so long as they are coherent and clearly expressed”"

I agree that your ideas are radical and clearly expressed, but unlike the PNAS paper I linked above they are not peer-reviewed.

I’m genuinely sorry that I can’t agree with your viewpoint, because I find the Aquatic Ape Hypothesis has a certain romance about. I would delighted and amazed if it were true, but the balance of evidence continues to weigh against it.

If we ever discover fossils of aquatic hominins, rest assured that anthropologists will reconsider their views. Until then, the Aquatic Ape Hypothesis remains little more than speculation.

http://newpapyrusmagazine.blogspot.com/2009/02/david-attenborough-on-aquatic-ape.html

Between 9 to 7 million years ago,Oreopithecus inhabited the swamp forest of the ancient island of Tuscany-Sardinia apparently specializing in feeding on aquatic plants. Oreopithecus was also a biped with strange feet that possessed a highly divergent hallux (big toe). Of course, now we know that another hominin, Ardipithecus, was also a biped that possessed a similar divergent big toe.

But was Oreopithecus a hominin? The discoverer of the most complete skeleton of Oreopithecus, Johannes Hurzeler, argued until his death that it was. But is there any evidence?

If you compare the cranio-dental morphology of Oreopithecus with humans, australopithecines, gorillas, chimpanzees, orangutans, and gibbons you discover that humans and australopithecines have the most cranio-dental similarities to Oreopithecus while gorillas, chimps, orangs, and gibbons have very few similarities with the swamp ape. And you find a similar pattern with the postcranial evidence.

But human ancestors probably went through two semiaquatic phases in their evolution. The first was a freshwater semiaquatic phase and the second was a marine semiaquatic phase. How do I know this?

Well, I know enough about marine mammals to know that there’s always a dramatic modification of the kidneys of marine mammals in order to deal with the ingestion of hypertonic fluids from the salt water environment. Being able to rapidly excrete excess salts from the body is essential for the survival of a marine mammal in order to avoid dehydration. Marine mammals have dealt with the problem of excess salt in their diets by developing kidneys with multiple medullary pyramids. This increase the surface area between the medulla and the surrounding cortex of the kidney, allowing for rapid processing and excretion of ingested hypertonic fluids. Most terrestrial mammals have unipyramidal kidneys except those that have semiaquatic marine ancestors. All catarrhine primates, including apes, have unipyramidal kidneys– except for humans. Humans have a radically different kidney morphology. Humans have kidneys that are unusually large relative to those of apes with typically 8 to 18 medullary pyramids. Clear morphological evidence of a marine phase in human evolution, IMO.

M.F. Williams Bioscience Hypotheses(2008)1,127-137 Cranio-dental evidence of a hominin-like hyper-masticatory apparatus in Oreopithecusbambolii. Was the swamp ape a human ancestor?

M.F. Williams, Morphological evidence of marine adaptations in human kidneys, Med Hypotheses 66 (2006), pp. 247–257.