Aquatic Ape Theory - What is it?

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... Anatomical Evidence
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... Descended larynx
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... Furlessness
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... Human ailments
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... Menopause
... Nose
... Olfactory sense
... Pachyostosis
... Paranasal Sinuses
... Platycephaly
... Reverse osmosis
... Sexual features
... Sleep (USWS)
... Surfer's ear
... Sweating
... Tears
... Underwater vision
... Viruses
... Waterside environments

. Homo Ancestors
... Trachillos bipedal hominids
... Homo erectus
... Homo neanderthalensis
... Sea Gypsies/ the Moken
... Homo sapiens - water afinity
... Coastal Migration
... Pan and Gorilla ancestry
... Semi-Aquatic Animals

. Testable Hypotheses
. Fossil evidence
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. Paleoecological evidence
. Retroviral marker in apes
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Paranasal sinuses (PNS)

The following paper was sent to Evolutionary Anthropology, which published the Rae-Koppe paper on paranasal sinuses, but they refused to publish it claiming that they do not publish replies. This is yet another example of how there persists an unscientific boycott of any paper supporting any part of the aquatic hypothesis. The authors have given me permission to quote their reply in full.

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Rae & Koppe (2015) use comparative data on paranasal sinuses (PNSs) to test the so-called Aquatic Ape Theory (AAT). Their data on PNSs are in full agreement to the littoral theory. We, very briefly, first give a summary of the coastal dispersal hypothesis of early-Pleistocene Homo, then provide some comparative data on PNSs, and finally discuss whether PNS anatomy confirms or disproves these views.

Sinuses and flotation: Does the Aquatic Ape Theory hold water?

• Marc Verhaegen, Study Center for Anthropology, Mechelbaan 338, 2580 Putte, Belgium
• Peter Rhys Evans, Consultant ENT/Head & neck Surgeon, The Royal Marsden Hospital, London

Rae & Koppe [1] in a recent paper in Evolutionary Anthropology on paranasal sinuses (PNSs) use comparative data to test the so-called Aquatic Ape Theory (AAT), concluding that it is not compatible. However, their (excellent) data on PNSs – as opposed to their interpretations of those data – are in full agreement to the coastal dispersal view of human evolution.[2][3][4]

We, very briefly, first give a summary of the Pleistocene coastal dispersal or littoral hypothesis, then provide some comparative data on PNSs, and finally discuss whether PNS anatomy confirms or disproves these views.

Pleistocene Homo dispersal along coasts and rivers

Up-to-date scientific discussions (pro and con) on our ancestors semi-aquatic past should be based on recent publications, especially the e-book on human semi-aquatic past, Was Man More Aquatic in the Past? [5]; the proceedings of the symposium last year on the same subject in two special editions of Human Evolution [6]; and some other recent papers in anthropological journals such as HOMO.[7][8]

Whereas most conventional approaches to hominid evolution usually consider only arboreal and terrestrial settings, we suggest that semi-aquatic habitats may also have been very important. This implies that the term ‘aquatic ape’ might be misleading to ill-informed or out-dated readers. [4]
The available comparative, embryological, fossil and palaeo-environmental evidence suggests that ‘AAT’ is not about apes or australopithecines or pre-australopiths and not about Miocene or Pliocene adaptations as proposed in most [9][10][11], but not all [2] early works on the subject, but in the first place about Pleistocene Homo dispersing intercontinentally; and not about having been fully aquatic, but about having spent a lot of time in shallow waters: ‘littoral’ is a more appropriate biological term here than ‘aquatic’. Our comparisons of extant and fossil hominoids with other animals in different biological subdisciplines refute the traditional open plain ideas (e.g. endurance-running, Savannahstan, ‘born to run’, Man the Hunter, ‘le singe coureur’), but instead confirm Carl Sauer’s conclusion, now more than half a century old, that “The seashore offered the best route of dispersal from continent to continent.” [2]

More in detail, the littoral hypothesis argues

1. that early-Pleistocene ‘archaic’ Homo erectus-like populations spread around the globe following the coasts as far as Indonesia, Angola and England (as exemplified by the coastal sites of Mojokerto, Dungo V and Happisburgh respectively) where they used stone tools to open hard-shelled foods and beach-combed, waded bipedally and dived for sessile littoral foods (e.g. parttime diving best explains archaic Homo’s pachy-osteo-sclerotic skeletons, i.e. the very heavy, thick and dense cranial and postcranial bones that provide hydrostatic ballast and are typical of slow and shallow diving tetrapods [5][7][12]);
2. that from the coasts, possibly thanks to improved tool manufacturing abilities, archaic Homo populations such as H. heidelbergensis and H. neanderthalensis followed the rivers inland (explaining their reduced pachyosteosclerosis compared to most H. erectus) where they collected shallow aquatic and waterside animal and plant foods, including cattails Typha and underground storage organs of waterlilies and grasses, traces of which have been found on Neanderthal tools or in their dental calculus; [13][14][15][16]
3. and that eventually early H. sapiens, thanks to more complex (composite and distance) tools, could abandon diving (explaining our loss of pachyosteosclerosis) and became long-legged waders and walkers, who, according to the isotopic (at least in Europe [17]), physiological and other evidence, exploited inland waterside and freshwater plant and animal resources, including shellfish, fish and/or (water)fowl.

PNSs help bring/keep the nostrils above the water surface

It should be obvious to well-informed students that the term ‘aquatic ape’ is meant as a catchy slogan, used by Elaine Morgan in the title of two of her books, and that nobody ever claimed that PNSs are an argument that human ancestors were ever fast and/or deep divers. On the contrary, para-nasal sinuses, like the word says, is air around the nasal passage (Figure 1) which hydrostatically helps bring or keep the nostrils and possibly the eyes (rather than the whole head) out of the water [18][19][20]. This obvious buoyancy result of having PNSs might well be compatible with other possible functions of PNSs (e.g. nitrogen monoxide NO production) which we have reviewed elsewhere. [19][20]

PNSs can appear and disappear during the course of evolution [1][19], for instance, bovids, small as well as large species, can have relatively large or small PNSs [21] (presumably according to whether they live in wetlands or else in arid regions, or have to cross rivers seasonally). Figure 1 in Rae & Koppe’s paper [1] on the presence of PNSs in diverse mammals is a helpful comparative summary, although it lacks subtlety, black-white dividing species only into those that do and those that do not have PNSs: when discussing buoyancy effects of PNSs, it would have been more informative if they had discerned at least between, for instance, absence of PNSs, presence of maxillary PNSs, presence of both maxillary and fronto-ethmoidal PNSs, and extensive PNSs.

Fully aquatic mammals lack PNSs, [1][19][20] arguably because PNSs are hydrostatically useless in established aquatics, might hinder diving, and, in deep divers, might be dangerous due to the high water pressure, with the risk of sinus collapse and hemorrhage. Since sea-water has a density of about 1.024 (as compared to 1.000 of pure water), PNSs are likely to be smaller or absent in marine and littoral tetrapods. For instance, freshwater crocodiles have much larger PNSs than marine crocodiles, and whereas hippopotamuses usually stand or walk on the river bottom and have small PNSs, very large PNSs, surrounding the nasal passage, are typically seen in wetland dwellers, most conspicuously in the long-nosed elephants, tapirs and swine. [19][20]

PNS size variation in Homo

Although exact data on PNS size and localisation comparing enough hominid specimens are still lacking, PNSs seem to have been larger generally in mid-late-Pleistocene pre-sapiens Homo (e.g. heidelbergensis, neanderthalensis, Steinheim, Petralona) than in most sapiens (who display considerable inter- and intra-population variation, suggesting PNSs might have lost some functions) and than in most early-Pleistocene Homo erectus. [19][20][23][24]. This is in agreement to our proposed scenario (which is based on other arguments [3–8]) that early-Pleistocene Homo spread along the coasts, that later archaic Homo ventured more and more inland along rivers (fresh water), and that early sapiens reduced diving and developed better wading and walking abilities [4–9]. It is of no surprise to us that Neanderthals, who had relatively large noses and mid-facial prognathism, also had well-developed PNSs, as well as dental calculus with traces of waterlily roots [15][16].

Recall that the littoral hypothesis (‘AAT’ sensu stricto) is not about African apes or australopithecines, but in the first place about Pleistocene Homo trekking intercontinentally along coasts and rivers rather than running or hunting on open plains. We have discussed australopithecine and African ape PNS size and basicranial pneumatisation as well as the possible relation with wetland-dwelling and surface-feeding elsewhere [20].

In conclusion, when the PNS data are considered in a non-emotional manner (i.e. not pro or contra so-called ‘aquatic apes’) they support rather than contradict the littoral hypothesis (coastal dispersal of early-Pleistocene Homo).

Figure 1. Computed tomography scan of the human nasal passage. Our nasal entrance is at all sides surrounded by PNSs: the right and left maxillary and (not visible in this transection) the frontal sinuses. https://www.flickr.com/photos/bionerd/2000890508/

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