The hand, this evolutionary prodigy

The human hand is a notable instrument. And inside the hand, that we have the thumb oponible it is really prodigious. Big Isaac Newton said:“ Only the thumb already would convince me in the God's existence”. Nevertheless, and although to have a finger oponible is a wise move, other primates also have it. Now then, his paws as the man cannot use the hand. For two causes. The first: the hand has two preys that can act of simultaneous form. We can take a ball with the palm and, simultaneously, support a pen with the first two fingers. And second: the union neural direct between the brain, more specifically the previous brain, and the hand by means of what it is called the pyramidal route. In the chimpanzee, for example, the hand is not provided so well from a nervous point of view, what does that his capacities turn out to be drastically wretched. The clearest example is that of the pianist: it can beat 10 times per second only with the index. Obviously, the hand of the chimpanzee is capable of taking fruit, of rising for the trunk of a tree, of drinking, of dressing up, of throwing stones and of poking an anthill with a stick. But the human workmanship meets the hand out of his scope.

And this that the hand humanizes, from a biological point of view, is not a big thing. To have a bone in the arm, the humerus, two in the forearm, the ulna and I remove, eight in the doll arranged in two tiers, five metacarpals in the palm and five fingers with three huesecillos - except the thumb that only has two - it is quite primitively. The amphibians also possess five fingers and other mammals have modified this ancient system. This way, the horses have ended with the only finger that allows them to run.

Nevertheless, she turns out to be advanced enough in some subtle aspects. During 50 million years our ancestors adapted themselves to an existence arborícola, with what they were developing a more agile previous member. Both the shoulder blade and the clavicle survived to provide a notable mobility to the arm. The elbow and the doll developed to allow the widest scale of movements. How many animals can each and everyone of the parts scratch of his body only with his previous members?

One of the most curious discoveries is that certain illnesses can "turn" in the hand. For example, the Down syndrome generally remains reflected in anomalous traces in the palms. In fact, there present less maelstrom, arches and radial handles in the tops of the fingers that who we do not suffer this genetic defect. The Mongolian ones present a major tendency to have these handles in the fleshy part of his ring finger while the normal people usually have them in the index. Also they have major tendency to present in the palm the called line simiesca, the horizontal and only line that crosses from side to side the area nearest to the fingers. Close to 80 % of the syndromes of Down it has it while only 7 % of the normal population possesses it, and normally in one of the palms.

Torrent Melrose Place (2009) S01E14 Stoner Canyon free