The Missing Two-Thirds of Evolutionary Theory

In this Element we give an exposition of what we believe to be 'biology's first law'. We believe that through this law we can throw light on hitherto-puzzling aspects of the evolutionary process, including the tendency of organisms to diversity and the somewhat vague, but unmistakable, progressive nature of the evolutionary process.

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In this Element, we extend our earlier treatment of biology's first law. The law says that in any evolutionary system in which there is variation and heredity, there is a tendency for diversity and complexity to increase. The law plays the same role in biology that Newton's first law plays in physics, explaining what biological systems are expected to do when no forces act, in other words, what happens when nothing happens. Here we offer a deeper explanation of certain features of the law, develop a quantitative version of it, and explore its consequences for our understanding of diversity and complexity.