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Savannah Apes from Rainforest Apes



This article covers an important stage in the origins of mankind and examines many of the factors which determined our characteristic form. It outlines the early transition stage from Rainforest Ape to creatures which I have named Savannah Apes, taking their name from the habitat they adapted to initially.


I will continue the discussion of the evolution of these intermediate forms into modern humans in a subsequent article.


Most, if not all, of our evolution was of the type which involved incremental improvement, by selection, of traits advantageous to survival in a given environment. This environment was the African Savannah/scrub-land.


In the article Mechanisms of Evolution I described how a change of habitat of an animal species can eventually bring about a profound change in that type of animal. The change from a tropical rainforest (semi-arboreal) habitat to a more open savannah is an example of a profound change of habitat.


It was the Savannah scrub-land of East Africa which provided the constraints which determined to a great extent our ‘format’ or characteristics as humans. But these characteristics are minor adaptations to the previous configuration which was appropriate for life in the African rainforest.


It can be assumed that some seven million years ago, a group of rainforest apes, living at the edge of the Central African Rainforest, decided to venture out into the areas of scrub-land on its eastern periphery. There are many reasons why they should want to do this - the most common one would be the stress associated with overpopulation.


It is difficult to speculate where this exact location would have been in Africa - but let us say it was somewhere in what is now the western border of Tanzania. The Google map of Central Africa indicates the rainforest area in dark green and the acacia scrub-land  and savannah in lighter green.


Another reason why it was likely this area is because there are two large lakes - Lake Victoria and Lake Tanganyika. These water resources may have played a part in attracting the first apes out of the rainforests. I have coloured these lakes on the map in turquoise. Once one departs from the thick canopy cover of the rainforest, the harshness of the equatorial sun is soon evident. Problems associated with dehydration could have been mitigated by regularly drinking from these resources.


Each new habitat makes its own set of demands on a pioneering species. The scrub-lands are dominated by trees and bushes of the various Acacia species, many of which are endowed with sharp thorns. Acacia tortilis (the umbrella tree) are amongst the few species of trees which these apes would be able to climb up into but they are sparsely distributed. The huge baobabs (Adamsonia) are quite common in this area but, because of their huge girth and smooth bark, these apes would have found them difficult to climb.


Assuming these pioneering apes still took refuge and nested in trees, to get from one tree to another would necessitate a lot of time on the ground and they would have been vulnerable to attack by predators such as lions and leopards - not to mention large sabre toothed cats which existed at the time. Gorillas are noted for wandering from area to area, never nesting in the same tree twice, so it is likely these pioneer apes would have moved around in a similar fashion.



I denote these pioneering apes as rainforest apes originally - as a general label for what could have been chimpanzees or gorillas. Similarly, as these pioneer apes get established in the new habitat I will name them savannah apes, a general term that covers many intermediate stages between rainforest apes and humans and avoids the pedantics of arbitrary hominid classification.


I would speculate that they were likely to have been more like gorillas than chimpanzee because gorillas are so much bigger, more aggressive and therefore more capable than chimpanzees of defending themselves from predators. Gorillas do spend less time in trees than chimpanzees and therefore must be more accustomed to challenges from ground based predators.


Predators such as lions seem to assess prey vulnerability by their height. They target the neck for attack in order to asphyxiate their prey with the grip of their powerful jaws. The taller the animal - the more difficult this may appear to them. If you look at the nearby photo of the male gorilla you will see that his height is increased by the hump on the top of his neck and head. A large male gorilla standing upright, mouth open to display his large canines, and defiantly staring - is likely to present enough intimidation to make the fiercest of predators turn away.


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Savannah with baobab
Thorn bush