The Evolution of Complexity
October 31st, 2006 Placozoan
ONE INCOMPLETELY understood puzzle in evolutionary theory is what is the driving force for greater complexity in a living system. Intelligent design proponents are heavily invested in the idea of complexity but disagree on how to measure it, with most measurements coming down to basic biomass. This is a poor means of measuring complexity, but the reasons for this are outside the scope of this article (for a short summary of some concepts in biological complexity see this article, sadly only available to subscribers). However, when considering a biological pathway we can probably agree that a pathway with only a few proteins is less complex than a pathway that fulfills the same role but uses many more proteins. Consider the clotting cascade. In simple chordates such as Amphioxus possibly only two or three proteins are involved (we don’t know the full details), while in mammals there are more than a dozen components. Research has demonstrated that the clotting system is not irreducibly complex, but the reason for this increase in complexity has not been previously determined.
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