Following up on their 2010 book Biology's First Law, in this Element the authors give an exposition of what they believe to be "biology's first law." They have labelled this law the "Zero Force Evolutionary Law" (ZFEL). It states: "In any evolutionary system in which there is variation and heredity, there is a tendency for diversity and complexity to increase, one that is always present but that may be opposed or augmented by natural selection, other forces, or constraints acting on diversity or complexity." This law is something with the status in evolutionary biology of Newton's first law of motion in mechanics – a background condition of stability. Brandon & McShea believe that through this law they 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.
1. The Zero-Force Evolutionary Law
2. What the ZFEL Is Not
3. The ZFEL Quantified
4. What the ZFEL Means for Biology