Kids&Science Life Evolution Why Are There No Three-Legged Creatures?	Index

Why Are There No Three-Legged Creatures?

There are many different ways of locomotion in nature.

Crawling, (without legs) like snakes and worms do, or on two legs as we humans explore the world. Most mammals move along on four legs, insects generally have 6 legs and spiders have 8. There are even species of millipedes with hundreds of pairs of legs.

Well, if we take living beings as our starting-point, we have already found our one-legged creature. The tree outside has only one leg, hasn’t it? It doesn’t need two. It does not have to move. Imagine trees wandering along on two legs. Most plants you know have only one "leg" for standing.

However, nobody has found a three-legged living being so far.

Take the daisy for an example. It would be very unfortunate for the daisy if it had to move. It would be far too energy-intensive for the delicate little plant to hop everywhere. It would probably require less energy to simply grow a second stem in order to consume less energy by moving on two stems in the future.

Let’s apply this to a three-legged living being. Since a body happens to have a certain shape and likes to move along on legs, it will produce as many legs as it needs for safely supporting the trunk. This guarantees a better chance of survival. The living being can hunt better, hide faster, climb better and many things more.

Even if a three-legged living being had occurred in the course of history, it wouldn’t have survived for long. The other living beings with a straight number of legs would have been superior.

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Last Update: 2004-Feb-29