So far I have paid homage to George Williams for his clear thinking about adaptation and natural selection, including his principle for evaluating whether a trait counts as a group-level adaptation (see part I). George was wrong when he made the empirical claim that “group-related adaptations do not, in fact, exist”, but it is thanks to his principle that we can say so. Providing the basis for proving oneself wrong is a high honor for a scientist.
Another enduring part of George’s legacy was his ability to speak in plain language. By his own account, he wrote Adaptation and Natural Selection to make the arcane knowledge that had developed within the field of population genetics accessible to a broader audience of biologists. His examples, such as flying fish obeying the laws of gravity and the distinction between a fleet herd of deer and a herd of fleet deer, had a parable-like quality that causes them to be remembered and recited to this day.
George’s gift for plain talk shows that the basic concept of adaptation can be easily understood, even though formal theory might also be important for working through the details. A mathematical model isn’t needed to decide that the wing-like fins of a flying fish are well adapted for gliding through the air. Even if we disagree about the agent or process that designed them (e.g., creationism vs. natural selection), we can agree that they are well designed for gliding and that this is very unlikely to have happened by chance. It’s equally easy to decide that the fins of the flying fish are individual-level adaptations, since they so clearly benefit the individual fish and not other fishes. What’s hard to understand?
Group-level adaptations are just as easy to understand, at least in many cases. We don’t need a mathematical model to decide that a termite mound or paper wasp nest is well designed, although models might well reveal design features (or failures of design) more subtle than meets the eye. In these cases, individuals are clearly building a structure that benefits not just themselves but a whole group. The same is true for the traits associated with human virtues that Darwin wrote about. Altruists and solid citizens generate benefits that are not confined to themselves, unlike flying fish fins. Group-level selection is required to explain the evolution of traits that benefit others or one’s group as a whole. What’s hard to understand?
Another simple point is that adaptations need to be evaluated on a trait-by-trait basis. For a human-designed implement such as a can opener, the parts that engage the can might be well designed while the parts that engage the hand might be poorly designed. For a species such as the flying fish, the fins might be well designed for the individual, the schooling behavior well designed for the group, and temperature tolerance poorly designed for global warming. The phenomenon of major evolutionary transitions, whereby groups become integrated in so many respects that they quality as superorganisms in their own right, is one of the most important developments in evolutionary thought–but it doesn’t change the fact that adaptations need to be evaluated on a trait-by-trait basis.
Williams’ Principle is important not only for the academic study of evolution but in everyday life. Cultural evolution is a multilevel process, no less than genetic evolution. What’s good for the individual is not necessarily good for the group. What’s good for one’s immediate relatives is not necessarily good for the clan. What’s good for the clan or political party is not necessarily good for the nation. What’s good for the nation is not necessarily good for the planet. The fact that adaptation at any level of a multi-tier hierarchy tends to undermine adaptation at higher levels is something that everyone needs to know about the evolutionary process. It shows that the concept of the invisible hand, whereby the pursuit of self-interest automatically results in the common good, is profoundly mistaken. Our lower-level strivings will continue to be part of our higher-level problems until all of us absorb the message of Williams’ Principle.