by Nathan Brouwer

Created on: June 06, 2008

First and foremost, organism do not necessarily always move towards more complex forms. It is fairly common for whole groups of organisms, or organs within organisms, to become less complex. The appendix once served a function in humans, but we've evolved to no longer require this organ. In this respect, our digestive system is less complex than it was previously. Aquatic mammals have given up the complex anatomy necessary for locomotion on land and "lost" their legs.

This all begs the question, however, of what we mean by "complexity." Complexity can exist at numerous levels. Organisms vary widely in the amount of genetic information in their genome, but larger, more complex genomes are not necessarily correlated with the complexity of other aspects of the organism. Individual plants can often duplicate their entire genomes, resulting in a phenomenally large amount of information. This complexity can often be deleterious, and relatively few plant species actually have these large genomes.

There can also be biochemical complexity in the various proteins, enzymes, and other molecular structures an organism utilizes. Many plants produce very complex, sophisticated chemicals - often defense chemicals to protect them from animals, though in the case of peppers these chemicals make them hot and tasty to humans. Organism can also show cognitive and social complexity. In terms of genetic and biochemical complexity, most primates are very similar. They vary tremendously in their social complexity, however, from monkeys, to chimps, to humans. Given these examples, it is very important that biologically be well defined.

It is also important to remember the fundamental similarity of all organisms. All living things use same basic system for storing and replicating genetic information. Regardless of whether a plant creates sophisticated alleochemicals to defend itself, dolphins communicate underwater, or bacteria live in the deep ocean off of geothermal energy, all of this "complexity" is coded with four DNA bases. All of the complex cellular or physical structures used to expresses this complexity are built with a repertoire of 20 amino acids. So, underlying all complexity is similarity and elegant biochemical simplicity. It can be argued that this genetic and biochemical system is the real miracle of life, and all the "complex" forms are just interesting iterations on this elegant system. The neutral theory of ecology, promoted by Steve Hubbel, actually argues that all organisms are equivalent ecologically regardless of their complexity or the niche they fill.

Finally, from a theoretical perspective, it is more likely for apparent "complexity" to evolve than a regression towards simplicity. For example, a "simple" organism like a bacteria can only shed a limited amount of things to become more simple There is, however, a whole possible realm of more complex forms it could evolve into. The random walk of evolution is limited against certain limitation on its lower bound. An organism can't shed certain fundamental functions. The sky is the limit, however, in evolving into apparently more complex biochemical, structural, and behavioral forms.

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