Mathematics Awareness Week 1995

The Production Line of Life

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Why does nature make such persistent use of symmetry? Symmetry is a very effective way to exploit successes, because it repeats the same structures over and over again. Because of symmetry, a structure that 'works' in its own right can be produced in bulk and used as a reliable building block.

Symmetry is also a way to trace the development of organic forms from an inorganic world. Early in evolution, the only structures available were those that could arise spontaneously through purely physical (or chemical) processes. Because the laws of physics and chemistry are symmetric -- they are the same at all positions in space and at all instants of time -- so are many of the structures that arise from those laws.

Evolution then is built upon these structures to produce ever more complex life forms. Any symmetries that led to useful organs or functions were preserved, such as the multiple legs of a centipede or the multiple vertebrae of the human backbone.

Virtually all living creatures have visible symmetries of form and function. Every structure that is repeated -- such as our two arms, but also our five toes on each foot and the many thousands of hairs on our heads -- is an example of symmetry, or of a symmetry that has been built on and slowly changed by evolution.

Pigs, polecats, and people are bilaterally symmetric -- their left and right sides are (almost) mirror-images of each other. Starfish have fivefold symmetry -- or tenfold, or nineteenfold, depending on the species. Snail shells have spiral symmetry, and delphiniums have five equally spaced petals.

Life is a production line, molded by genetics but driven by dynamics. It is the result of a partnership between genetics and dynamics -- biology and mathematics. Mathematics Awareness Week, the last week of April, is a time to remember that we are not just a collection of genes. All multi-celled creatures have a hidden symmetry at the very core of their being.

Back to Math Awareness Week 1995

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