Conrad Waddington was a developmental biologist who is perhaps most famous for his illustration of the epigenetic landscape. For fun I’ve been reading his 1957 book The Strategy of the Genes, a classic text in evolutionary and developmental biology. I came across this passage that I found interesting:

The meaning of natural selection can be epigrammatically summarized as ‘the survival of the fittest’. Here ‘survival’ does not, of course, mean the bodily advance of a single individual outliving Methuselah. It implies, in its present-day interpretation, perpetuation as a source for future generations. That individual ‘survives’ best which leaves the most offspring. Again, to speak of an animal as ‘fittest’ does not necessarily imply that it is stronger or most healthy, or would win a beauty competition. Essentially it denotes nothing more than leaving most offspring. The general principle of natural selection, in fact, merely amounts to the statement that the individual which leaves most offspring are those which leave most offspring. It is a tautology.

  • Conrad Waddington, The Strategy of the Genes (chapter 3; pp. 64-65)

Interesting – but false. Waddington’s explanation for the first term, survival, is correct, but he makes a logical error in his explanation of the second, fittest.

Survival is, like Wadding puts it, perpetuation of genetic material. Wadding next claims that fitness does not necessarily imply strength, health, or beauty, which is correct, but his following claim is an error: that “[fitness] denotes nothing more than leaving most offspring”. On the contrary, fitness does not denote simply leaving more offspring, but rather symbolizes the nonrandomness of leaving offspring. Nonrandomness is a critical part of the definition of fitness. If number of offspring were random, there would be no concept of fitness, even if some individuals left more offspring than others.

Take a thought experiment: in a computer simulation where two organisms leave a random number of offspring, we would not use the word fitness to describe why one simulated organism left more offspring. Neither simulated organism was really more fit – a more appropriate word would be luck. Therefore, the entire point of the word fitness is to suggest that survivors are not determined randomly, but by something else. That “something else” is fitness, which does not explicitly suggest what determines fitness or how to measure it. The point of the phrase “survival of the fittest” is simply that the concept of fitness (nonrandomness) exists.

“Survival of the fittest” can be more appropriately rephrased as “success is nonrandom.” Survival, or perpetuation of genetic material, is success. Fitness simply implies nonrandomness in that success: Success is not distributed haphazardly, but according to a very complicated function derived from attributes of both the organism and the environment in which it exists. With this deeper understanding of the concept intended by the word fittest, it is clear that the phrase “survival of the fittest” is not a tautology, but a simple declaration of a fundamental principle in biology: that success is nonrandom.