The Adaptation Of The Opposable Thumb

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The opposable thumb is an adaptation that is present in humans, non-human primates such as chimpanzees, gorillas, orangutans, old world monkeys. Opossums and giant pandas.
Most primates have opposable thumbs
By definition an opposable thumb is ’A thumb that can be placed opposite the fingers of the same hand. Opposable thumbs allow the digits to grasp and handle objects’
An opposable thumb is one which can oppose the rest of the digits on the same hand and can allow pad to pad touching.
The thumb is the only digit that can face the other fingers and enables its grip to hold objects which it would be unable to do otherwise (Wikipedia)
• Opposable thumb can simultaneously flex, abduct and medially rotate (pollex)
• Bring tip into opposition with other digits
• This is done by a sellar (saddle-shaped_ joint between the wrist bone that supports the thumb and the first metacarpal
• This allows approx 45* range of rotation along thumbs own axis
• Other primates also have this pollical opposability

It is often said that the evolution of an opposable thumb has led to development of tools.
It has been proposed that chimpanzee like apes began to through rocks and swing clubs at adversaries and that this behaviour yielded reproductive advantages. (CITE)
The improved precision and power of the hand muscles and its morphology leads to the prediction that the hand in humans has evolved and been adapted for
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