|MadSci Network: Anatomy|
First, why do we have them? Although the earliest land animals had various numbers of toes (and/or fingers) those that had five fingers and toes won out in the struggle for existence. These pentadactyl (five toed) creatures established the ancestral (primitive) pattern for all land dwelling vertebrates. So the real question is not why do we have five toes, but why would we have less than five toes? In the evolutionary process the basic body plan does not change unless two things happen. First, a genetic trait has to appear (through mutation or through a novel recombination of established traits) that allows for the change. Therefore, all vertebrates will have five toes unless they possess a "gene" for fewer toes. Second, that gene must somehow confer an advantage on those who have it. Cursorial animals (runners) actual walk on the tips of their toes. It is advantageous for them because it increases their running leverage, and allows them to run faster. In other creatures, toes are part of a grasping foot, and that's where more recent human ancestry comes in. Humans are primates, a group of animals that was initially adapted to living in trees. When you are a tree dweller it is advantageous to have a grasping ability on all your limbs. This ability is a defining characteristic of the primate group. When human ancestors left the trees they became more adapted to running on the ground. Part of this adaptation expressed itself through shorter toes. This adaptation was advantageous because running on the ground was more important to the early human lifestyle than was climbing in the trees (a lot of scientific debate now centers on how "tree adapted" or "ground adapted" early human ancestors actually were). Our body design is determined by our evolutionary ancestry. We have toes because our ancestors had toes. Although human toes have become shorter in our evolutionary history, there is no reason to think that they will disappear completely in the future. Remember, body design changes only if a new genetic pattern appears that is advantageous. New genetic patterns will not appear simply because we want them to appear. And, given modern culture, modern medicine, and _shoes_ there is no reason to expect that there would be any advantage to a gene for fewer toes even if it did appear. Finally, why do we need toes? Nearly every walking animal has toes. The toe, in humans the big toe or hallux, is the last lever used to push off the ground during walking. Without that toe, the mechanics of walking would be very difficult, and not very efficient. So, why do we have/need toes? We have them because our ancestors did. We need them to walk efficiently.
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