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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'Aquatic Ape' Theory: Multiphase model

Hardy asked the question: "Was man more aquatic in the past?" The answer is almost certainly 'Yes'. But when? Where? and How?

What most anthropologists reject is the idea that an ape entered the water, and a human emerged. Nobody is really suggesting that anymore. Instead, the most parsimonious explanation is that there were multiple phases and different stages of a semi-aquatic lifestyle for our ancestors, and one possible hypothesis is offered below.

Phase 1: (16 - 9 mya) Aquarboreal Miocene Apes 

There were up to a hundred of species of Miocene apes living in mosaic environments during the Miocene, in Eurasia and in Africa - for example mangrove forests, coastal forests, river deltas, savannah marshes and wetlands. They would have spent much of their time below branch, arm over arm, wading through the water, or on the shoreline feasting on crabs & shellfish as many monkeys and apes still do today. Already orthograde, the transition from a quadrupedal form of locomotion in the trees, to a bipedal form of locomotion in the water and hence on land, would have been a subtle yet obvious shift. With more coastline than anywhere else, the southern coasts of the Mediterranean would have been an obvious place for apes to have transitioned to an even more aquatic niche during the mid-Miocene.

"The features that typically distinguish apes from monkeys (i.e. large size, tail loss and arm hanging) could have been adaptations for what we call an ‘aquarboreal’ locomotion in an environment that included both trees and water. A vertical posture and an ability to climb with the arms raised above the head could have helped a wading primate to enter or leave the water by grasping overhanging branches or waterside vegetation, and to grasp fruits above the water. Body enlargement and tail reduction would hinder agile arborealism, whereas a larger body is more easily supported in water and helps reduce heat loss (explaining why aquatic mammals are larger than related terrestrial forms). Tails would be of little use for a wading and/or swimming primate and would cause both drag and heat loss."

(From "Aqua-arboreal Ancestors" [Paper] by Marc Verhaegen, Pierre-François Puech, Stephen Monro [pdf]

Phase 2: (9 - 5 mya) Swimming Late Miocene Hominids.

As global climatic changes occured towards the end of the Miocene, especially during the Messinian when the Mediterranean dried up (MSC) and coastal forests began to disappear, these European aquarboreal apes would have had to adapt to a more coastal niche. With more attention now focused on a Eurasian origin for the LCA of chimpanzee and humans, we could hypothesise that a number of species that did survive around the Mediterranean into the late Miocene (such as Graecopithecus) would have had to survive on aquatic foods that they may have had to swim and dive for, as the Mediterranean coast shrank and its many islands became connected to the mainland. Evidence of a fully bipedal hominid, speculated to be the LCA of Pan/Homo, has been found on the island of Crete, their footprints very similar to ours, left in the rocks by the sea at a time when the sea was beginning to disappear.

Phase 3: (5 - 3 mya) The Pliocene Missing Link

Possibly due to looking in the wrong place, no evidence has yet been found of a transitional fossil between African or Eurasian hominid apes and the appearance of fully human Homo erectus. Paleontologists, searching in Africa have found a number of species that they attribute to our direct line of ancestry (eg: Austrolopithecus, Ardipithecus, Paranthropus, etc.) but despite clear signs of bipedality in many species, there are too many differences to assign them to Homo, and too many similarities with Gorilla or Chimpanzee, (such as brain size, tooth morphology, etc.) Indeed, viral data suggests that our ancestors could not have been in Africa at all during the Pliocene. Instead, I propose that those late Miocene Hominids from Phase 2, may have made their way around the drying coasts of the Mediterranean, via Anatolia or across landbridges, not into Africa - yet - but down the Arabian peninsula, following the coasts into southern Asia. Most of our many aquatic adaptations probably come from this period. Over the course of a couple of million years, the definitions of what makes us human first appeared. From hominids they adapted to a more littoral existence, losing their fur, developing a subcutaneous fat layer, increasing their brain capacity, changing their sweating and kidney  functions to adapt to a marine diet, and emerging in the Pleistocene as our direct ancestor, Homo erectus. H. erectus was possibly the most aquatic of all our relatives, becoming at one time so dependent on aquatic resources that it became a proficient diver and could remain underwater for longer periods than we can today. 

(Could Homo floriensiensis have come directly from this intermediate ancestor? Making its way across to Flores while the island may have been connected to the mainland some 5mya, or swimming there? Evidence suggests that they may not have been direct descendants of erectus, but instead perhaps their LCA was this pliocene Middle-eastern/Asian hominid?)

Phase 4: (3 mya - 0.35 mya) Pleistocene Littoral Homo

From the southern coasts of Asia, Homo erectus spread east towards China and west towards Africa, north into Eurasia and south to Indonesia. By far the most successful of all Homo species to date, due to the duration of its existence and wide distribution of its fossils, erectus was undoubtedly a fully littoral/coastal species which can be seen in its biology. With heavy dense bones, a flat skull, a wide and deep thorax for large lungs, a large brain from a diet rich in marine foods, the abundance of clam-opening hand-axes and shell-middens, etc. it's clear that Homo erectus regularly dived for its food and was fully dependant on a coastal niche. During the Pleistocene, sea levels dropped by 100 metres during glacials, leaving vast regions available on the continental shelves during glacials. These areas would likely have had scarce trees and may have been rich in shell and crayfish.

By at least 2 mya Homo erectus was in South and East Africa, most probably having crossed into Africa from the Arabian peninsula some time earlier. There is some speculation as to whether erectus even built rafts or boats and sailed to distant shores. Fossils of African Homo might be the same species or closely related, ie: Homo ergaster, Homo habilis, Homo rhodensiensis. We also see many different divisions within the homo line in Europe: Homo georgicus from circa 1.7 mya may have followed the coasts and rivers from South Asia, and then subsisted on a large inland lake; H. antecessor known from 1.2 mya fossils in Spain, H. heidelbergensis in Germany at circa 640 kya may have been the LCA of Denisovans and Neanderthals. All these species were gradually more cold adapted than erectus, especially Neanderthals with their large lung capacity, and ear exostoses suggesting frequent cold water diving during the last ice-age.

Phase 5: (350 kya - 50 kya) Holocene Wading Sapiens

But somewhere in Africa, possibly around the Afar region of Ethiopia around 300 or more kya, a group diverged from African H. erectus/ergaster/habilis, becaming more terrestrially adapted possibly due to climatic changes at that time. They developed a much more gracile skeleton: taller with longer, thinner legs - often seen in wading animals - and a much less stocky frame than erectus or neanderthal. This species had less heavy bones and a reduced lung capacity, suggesting a redirection to a more terrestrial environment with more walking or running than diving. They had a flatter face, smaller nose and higher forehead, rounder brain cases - no flat skulls - with eyes positioned under the frontal brain, with extreme basi-cranial flexion - an improvement for looking down into the water - and other adaptations which suggest they transitioned from swimming/diving littoral homo to wading/fishing/hunting Homo sapiens.

Homo sapiens ventured into Europe probably several times, at least as long ago as 210,000 years ago, but initially failed to thrive there, whereas Neanderthals were already well-established. Most humans today are descended from a group of Homo sapiens that finally radiated out of Africa probably around 70-50,000 years ago, and inter-breeding at different times with Denisovans and Neanderthals, as is reflected in our genome. Not long afterwards, Neanderthals and all remaining Homo species became extinct, leaving Sapiens free to dominate the globe.

What about the African Hominids? 

Much attention has been paid to African fossils from 7 - 2 mya, with most paleontologists still believing that Homo originated in Africa. Everyone has heard of "Lucy" a species of Austrolopithecus afarensis that was clearly bipedal and lived in South Africa about 3.8-2.9 mya. Who doesn't want to find a human ancestor fossil? And if it was bidpedal, it must have been a human ancestor, right?

Wrong. Evidence is starting to accumulate suggesting that most of these fossils are closer to chimpanzees and gorilla than to humans. I believe that what may have happened is that the ancestors of gorilla may have split from European dryopiths, perhaps Oreopithecus, 10-7 mya (phase 1) and crossed land bridges to northern Africa where they followed the Libyan river systems down to lake Chad. They remained more 'aquarboreal' and some returned to the forests. Thus: Sahelanthropus -> Ardipithecus > East African robust apiths, etc. > Gorilla.

The ancestors of chimpanzees, may have diverged from our swimming miocene ape ancestors (phase 2) either in Europe (crossing from Sicily to north east Africa land bridge), or from the Arabian peninsula. Pan went right. Homo's ancestors went left. As Pan descended from already "bipedal" swimming apes, they continued to demonstrate "bipedal" morphology over the next few million years in Africa, as they continued to live in river deltas or lakeside habitats, partially aquatic and living off clams (Oldowan tools probably made by apiths: chimpanzee ancestors). Eventually, they returned to a more terrestrial/arboreal environment, but instead of walking on two legs, they became knuckle-walkers, something our own ancestors never did. Thus: South African gracile apiths > Chimpanzee/Bonobo. Gorilla and chimpanzees today lack underfur, suggesting that they may have at one time lost their fur. The unborn chimpanzee fetus develops plantigrade flat feet in utero, before reverting to a more handlike foot before birth (C.S. Coon), suggesting that their ancestors once had flat feet, as did many pliocene African hominid fossils.

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