Mmm i think (but i'm not sure about this) that several million years ago, the jungles of Central Africa cleared due to climatic changes. The apes in that area were therefore unexpectantly dumped into the savannah, a totally new environment that they weren't evolved to fit in.
The evolutionary pressure from the environment was huge since apes can't run very fast (and indeed human beings are among the slowest large animals on the ground.)
Other animals probably took a different route. The earliest human beings had features that were, by luck, already in the 'direction' of the evolution of intelligence. For example:
- Apes, in the jungle, were already capable of limited upright movement. This freed up the forelimbs and thus hands.
- The fingers of primates are very well developed for grasping branches. On the savannahs, there were no branches to grasp. Thus human beings learnt to manipulate other objects with their agile fingers.
(Animals which were already on the savannah, on the other hand, had hooves/paws on their forelimbs because they had long ago evolved to move on the savannahs. It was the most efficient way to run, but it wasn't conducive to using tools.)
Tool manipulation is obviously very intelligence-intensive, and the lives of the earliest humans depended on these tools, because every part of their body was evolved for the jungle, not the savannah. Thus the pressure to evolve intelligence.
Now i'm not totally sure about this but this is my understanding.
The evolutionary pressure from the environment was huge since apes can't run very fast (and indeed human beings are among the slowest large animals on the ground.)
Other animals probably took a different route. The earliest human beings had features that were, by luck, already in the 'direction' of the evolution of intelligence. For example:
- Apes, in the jungle, were already capable of limited upright movement. This freed up the forelimbs and thus hands.
- The fingers of primates are very well developed for grasping branches. On the savannahs, there were no branches to grasp. Thus human beings learnt to manipulate other objects with their agile fingers.
(Animals which were already on the savannah, on the other hand, had hooves/paws on their forelimbs because they had long ago evolved to move on the savannahs. It was the most efficient way to run, but it wasn't conducive to using tools.)
Tool manipulation is obviously very intelligence-intensive, and the lives of the earliest humans depended on these tools, because every part of their body was evolved for the jungle, not the savannah. Thus the pressure to evolve intelligence.
Now i'm not totally sure about this but this is my understanding.
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