MadSci Network: Anatomy

Re: Why do we have/need toes?

Date: Tue Mar 17 09:15:08 1998
Area of science: Anatomy
ID: 887720764.An

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 

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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