[Evolution of the hand]

The skeleton of the human hand has its evolutionary origin in the anterior fin of primitive fishes following a reduction process. Starting with 20 to 30 elements, the number of bones reduces to eight. This does not follow a continuous pattern but is influenced by environmental factors. This becomes particularly evident when considering the development of the opposition of the thumb. The muscles of the hand evolve from dorsal and palmar compact plates which are divided into two layers. The differentiation process follows the development of the fingers. The development of the individual hand is controlled by a group of homeobox genes. Comparable genes are found in many different species. The more recent evolution of the hand can be understood as the expression of the development of the brain. Therefore, the hand is a direct tool of our consciousness. It is a main source of differentiated tactile sensations as well as a precise working organ. Gestures, finally, are direct expressions of our personality.