Under the Microscope: A first-year medical student once solemnly told me: "I see the human body as the perfect machine." The idea that natural designs are superior to those formulated by human ingenuity is common. Aristotle declared: "If one way be better than another, that you may be sure is nature's way."
Charles Darwin took a less rosy view of the quality of much biological design and declared: "What a book a Devil's chaplain might write on the clumsy, wasteful, blundering, low and horridly cruel works of nature." In his book Cats' Paws And Catapults: Mechanical Worlds Of Nature And People, Steven Vogel compares the designs found in the biological world with the engineering designs that have flowed from human ingenuity.
Evolution, working unconsciously through natural selection, is the architect of the designs found in the biological world. The designs we find in our buildings, machinery and various technologies are products of human imagination and ingenuity. There are many important differences between evolution and engineering.
Evolution can produce new designs only by modifying existing designs, for example, and significant new designs are usually arrived at through a succession of graded intermediate designs. Obviously, engineers and architects need not restrict themselves to modifying existing designs but can strike out in new directions.
Because the processes of natural design and human design are so different there is no reason to expect that all human designs have been prefigured in nature or to expect that natural design is always superior to human design. For example, Vogel points out that such fundamentally important human designs as wheels with axles, metallic materials and long ropes made of short fibres are either absent from the library of natural designs or only very dimly prefigured there.
It is argued that wheels would not have been useful to early life because of the rough surfaces encountered by most terrestrial organisms. That argument doesn't hold up for aquatic and aerial environments, however, where rotary propellers would work at least as well as, and often better than, beating wings and fins.
In human technology wheels are used for much more than rolling vehicles around. They are used in gears, chains, belts, pulleys, cams, crankshafts, roller bearings, flywheels, turbines and much more. No counterparts of these devices are found in the biological world.
Metals are widely used to make rigid frameworks in human-engineered structures. Nature does not use metals for this purpose and builds rigid frameworks, such as bone and wood, from complex chemical composites. Metals have different mechanical properties to these composite materials.
If metal is lightly loaded it deforms elastically, returning to its former shape once unloaded. If it is loaded heavily it deforms plastically and retains this new shape once unloaded. It is therefore possible to press metal into useful shapes. This is not possible with composites, where material and shape must be fashioned simultaneously.
Civilisation discovered at an early stage how to make long, strong ropes from short fibres. The traditional short fibres generally used to make ropes occur naturally in hemp and sisal. A random array of fibres is laid out lengthwise and twisted. The harder the twisted array is pulled, the tighter the fibres bunch together and the higher the resistance to sliding becomes. Nature never incorporates short fibre into ropes in the way people have learned to do.
Modern civilisation would be unimaginable without engines. These engines mostly work by harnessing energy differences between hotter and colder regions. There are no significant differences in temperature between different parts of a biological organism, however, and so biological engines such as muscle cannot exploit temperature differences. Nature designed chemical engines that work in an isothermal environment.
One enormous difference between the biological world and the engineered world is that the former is in a state of constant turnover while the latter is static. Your bodily structure is constantly being broken down and replaced. There is scarcely an atom in your body today that was there a year ago - the former atoms were substituted with new atoms. A human-engineered device does not undergo dynamic turnover and repair, so it gradually wears out.
These are several reasons why the biological world is an equilibrium between build-up and breakdown. Turnover allows organisms to react quickly and flexibly to changing environmental conditions - if food is scarce, for example, you can slow the rate of breakdown. Also, the dynamics of turnover makes it easier for organisms to maintain their internal order.
The biological world has been unable to design many devices available to the human engineer, but nevertheless it has produced solutions of great sophistication and durability. The solutions produced by nature are not always superior to human-engineered solutions, but they are well worthy of study by engineers because nature has gone about things differently.
William Reville is associate professor of biochemistry and director of microscopy at University College Cork