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Reading Throughout the world, people understand the symbol of a clenched fist: it signals readiness to fight, because it is the natural weapon of man. This is also reflected in the shape of the hand, now two US researchers. Concentrated on the fist, the wide palm, the relatively short fingers and the long thumb form an optimal shape to simultaneously provide strength and protection for the joints. In addition to its use as a fine motor tool, rabid use could have influenced the shaping of the hand in human evolution, say the scientists. The hands are one of the secrets of success of man. With their help, we create objects and perform complicated movements - from the production of a hand ax to the making of fine drawings to the playing of sophisticated piano pieces. In the developmental history of man, the shape of the hand has increasingly adapted to these fine motor tasks. The idea that use as a weapon might have played a role came from David Carrier and Michael Morgan of the University of Utah looking at the hands of chimpanzees. Our closest relatives in the animal kingdom have hands with comparatively long palms and a small thumb. They can not form the compact shape of the human fist. If dexterity had been the only driving force in the evolution of the human hand, the thumb could have been longer, Carrier and Morgan thought. Thus, the shaping of our hand could be a typical human adaptation.

The shape of the fist is effective and protects the hand when striking

To investigate this hypothesis, the researchers literally carried out relevant experiments. They asked subjects to take blows on a special punching bag equipped with sensors. In addition, the researchers systematically examined the effects of a punch on the individual parts of the hand.

The Carrier and Morgan scores showed that a fist is the most effective blow compared to other hand postures. At the same time it is well cushioned by the impact of the blow against the joints and limbs of the hand, so there is less risk of injury. In a typical fist, the fingertips rest on the upper part of the palm, and the thumb presses on the middle links of the finger bones to the ring finger. In the case of a blow, the pressure which acts on the finger bones is passed on to the palm of the hand, and the thumb additionally supports from the outside. A monkey's hand can not take this position, but the proportions of the human hand seem to have been created for this purpose, say Carrier and Morgan. display

From an evolutionary point of view, therefore, there is a plausible picture: human ancestors who could deal hard fists without risking the risk of a hand injury had advantages. They were able to prevail in the fight for resources or partners. "Man is a being whose natural behavior includes aggression and violence, " say the scientists. In addition to design features, this side of man is reflected in his hands, Carrier and Morgan are convinced.

David Carrier and Michael Morgan of the University of Utah: Journal of Experimental Biology, doi: 10.1242 / j eb.075713 © wissenschaft.de - Martin Vieweg

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