Aquatic Ape Theories: Human Evolution on the African Savannah or Coast

The Great Apes seem to be our closest relatives and it is thought that our ancestors separated from their line several million years ago. A number of now extinct apes developed bipedalism (walking upright on two legs), as did our own ancestors. It was obviously to their advantage – obvious because they survived for a long time – but the question is: "What was the initial advantage of leaving the trees and walking on two legs?" There are two main theories.

Aquatic Ape Theories

One suggestion is that there was a good living to be made on the sea shore for any ape that left the forests to exploit it. Gradually adopting an upright stance would have been useful since it would free the hands to poke around and find food, while maybe also allowing the ape to wade into deeper water. Some suggest that a semi-aquatic past can also explain many modern human peculiarities (reduced body hair, subcutaneous fat, and our descended larynx for example).

When the African climate began to change (several million years ago), savannah grassland started to replace much of the ancient equatorial forest. As this new habitat developed it provided a place where an ape could prosper if it "came down from the trees". Why it might have been an advantage for such an ape to walk on its hind legs is unclear, and theories include those which suggest that presenting the smallest surface possible (the head) to the midday sun was crucial, and others which stress the ability to see further and thus become aware of the approach of predators much more quickly.

Evidence

It is never going to be possible to be certain why some species of ape adopted bipedalism, but it ought to be possible to find out when and where it first happened. Fossil bones can be studied and dated, and associated fossil remains can establish what the environment was like. The conditions that favour the fossilizations of the remains of a dead animal are very good along the sea shore, and relatively poor on open grassland. To date there is no fossil evidence from coastal deposits, and the only information we have comes from the savannah.

Recent Aquatic Ape Theories

Once apes had developed their ability to walk upright out on the savannahs of Africa (for whatever reasons) it is possible that our ancestors might have found life beside the sea provided rich pickings. Theories suggesting that adapting to a life on the coast was the original reason for our bipedalism date this event to around 6 million years ago, while those which have two legged apes adapting first to the grasslands and then later adopting an aquatic habit use a date of around 2.5 million years.

Modern Aquatic Apes

Whatever happened in the past it is true that there now is an ape that enters and exploits the sea. In the past it took many generations for animals to move into new environments because they had to wait for genes, and with them anatomy and behaviour, to change. Now, by exploiting modern technology, modern humans are truly becoming "Aquatic Apes".

Dec 9, 2008 1:25 PM

Guest :

Hi, i` m laura, i can understand your reasoning and agree with you about Aquatic Ape theories, i do much reasearch about Primates and there surrondings and i find it quite intersting, so thank you!!!

Jan 28, 2009 12:19 AM

Guest :

'no evidence from coastal deposits'. I don't think that this is correct. In The Aquatic Ape Hypothesis by Elaine Morgan she mentions turtle eggs that were found along with the hominid remains known as Lucy. There is a bias against taking note of marine fossils, because fossils are best preserved in a watery environment! It is a conundrum.

I've just found this in Elaine Morgan's latest book, the Naked Darwinist. Of course she explains it better:

Almost all the hominid fossils are of specimens that died by the water’s edge, and their
bones sank into the silt and were thereby fossilised. In many cases they were accompanied by the
remains of fish and crabs and turtles and crocodiles and the odd hippopotamus - but also by occasional
land animals. The conclusion drawn from this was that one of our plains-dwelling ancestors had come to
the lake or river to drink, and happened to die there. What could be more probable? They had to die
somewhere, and the remains of the vast majority assumed to have died on the arid plains would have
been eaten by predators or scavengers, and left no trace. It is known as “taphonomic bias.” It was and is
perfectly true: the fact that their bones sank into the silt can never prove that they lived by the water. But
just as certainly, it can never prove that they did not. So that settles nothing.

Feb 17, 2009 3:14 PM

Guest :

"Why it might have been an advantage for such an ape to walk on its hind legs is unclear"

Personally, I can't help but think that the reason for bipedalism on open terrain is painfully obvious: It's efficient. Bipedal locomotion is much slower than quadrupedal, but requires much less energy. For animals that might have to roam in large open distances, requiring less food in the long term, and being able to run much longer distances without tiring in the short term, are clearly major advantages.