Aquatic Ape Theory - What is it?

A Brief Summary of AAT - key arguments

A Brief History and Key Proponents of AAT

When / Where / How?

Ape to Human Evolution Timeline

Alternative theories of human evolution

Wikipedia and the scientific community

... Anatomical Evidence
... Bipedalism
... Birth and babies
... Brain
... Breath control
... Descended larynx
... Diet
... Diseases
... Fat
... Fingers, toes and feet
... Furlessness
... Hair and baldness
... Human ailments
... Kidneys
... Language & Song
... 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
. Genetic evidence
. Paleoecological evidence
. Retroviral marker in apes
. Acheulean handaxes

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Homo habilis

The endocranial capacities of Homo habilis reveal a mean value of 640 cm³ [60]. This mean value exceeds the latest
available mean value for Australopithecus africanus (451 cm³) by 189 cm³. That is, when we compare the values for
samples reasonably attributed to these two taxa, we find that the H. habilis value for mean absolute endocranial
capacity exceeds that for A. africanus by 42%. When the absolute capacity values are related to estimates of body
size, values may be obtained for relative brain size. These, too, show that H. habilis was significantly more
encephalized than A. africanus. When these Encephalization Quotient values are expressed as percentages of the
modern H. sapiens relative size, the value for A. africanus falls at 46% and that of H. habilis at 53%. That is, of all
fossil hominin series for which these values are determinable, H. habilis is the earliest hominin species whose mean
index of encephalization is over half the mean index in modern H. sapiens. All of the determinable australopithecine
species have values definitely below 50%.
It is a striking fact that this increase in inferred brain size first becomes evident with the appearance of H. habilis. The
earliest examples of the latter species occur in the fossil record after major African tectonic changes of 2.6-2.5 Ma, which led to drying and cooling of large parts of the continent. These, in turn, would undoubtedly have affected the water
resources available to the early hominins. The drying-up of many streams might be expected to have set water supplies at
a premium. Moreover, the tectonic elevation would have increased run-off and induced reversals of the direction of flow
of some rivers. All of these direct and indirect sequelae of tectonic upliftment, added to the general climatic desiccation,
would have made water a more precious commodity to those living in the affected areas.
Under these more straitened conditions, we may reasonably infer that an even closer relationship between Man and
water than before would have been of intense survival value. I envisage that such close relationship would have
involved not only water for drinking and keeping cool, but also increased dependence upon aquatic food resources.
At a time when selective pressures for larger brains must have been strong, the ‘brain foods’ required were
accessible by greater, probably culturally influenced foraging on aquatic plants and animals. By such a route, it is
not difficult to envisage a causal link, or set of links, between the more exacting challenges for survival and the
selectively determined and palaeontologically testified increase in absolute and relative brain size. Water and aquatic
living things provided the crucial catalyst when early Homo confronted this evolutionary bottleneck. While many
species did not survive the crisis of 2.6-2.5 Ma, the hominins, some of whom were armed with genetic mutations for
larger brains, a penchant for water foods, and stone culture, won through to become the diverse larger-brained
species of Pleistocene mankind.

[Philip Tobias. Was Man More Aquatic in the Past? p.11-12]

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