(Re: In the continued debate over high school science textbooks in Louisiana, whereby a local opponent of evolution, Judge Darrell White, insisted on connecting the Columbine High School massacre to the teaching of evolution through the phrase “survival of the fittest.”)

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When we summarize things we have to be careful that we don’t lose meaning or invite misinterpretation, for instance the phrase “survival of the fittest.” This was first used as a summary of natural selection, which is one of the mechanisms of evolution, but today it is mistakenly and inaccurately used to summarize the entire theory of evolution.

Based on the current usage of the words in the phrase we might be driven to think “survival of the fittest” means: Those individuals that are physically superior to other individuals will continue to live. Perhaps there is even a suggestion that the “fittest” should actively work to kill off the weak (weak being opposite of fit). Indeed people have and do use this phrase to justify the strong taking advantage of the weak, the rich taking advantage of the poor, etc.

However the phrase “survival of the fittest” was originally meant to be a concise summary of a more complicated idea. Over the more than a century and a half since the phrase was originally coined we have learned more about how nature works and today the phrase “survival of the fittest” is an out-of-date inaccurate oversimplification that no serious biologist uses in a meaningful way.

The phrase was coined by Herbert Spencer and first used in 1864. At this time, “fitness” was not referring to physical prowess but how well an organism was adapted to its present environment. For example, during a dry year individuals of plant species X that require less water to grow are “fitter” than individuals of the same species that require more water. The individuals that require less water are more likely to survive. Traits, such as water use, are heritable, so those survivors, the “fittest,” are more likely to pass their traits on to the next generation. This scenario, where individuals with traits favorable to the present environment are more likely to pass those traits to the next generation, is called natural selection.

But our study of life on Earth didn’t stop in the 19th century! As new observations are made, as our tools, technology, and techniques get better we are able to expand our understanding of how nature works. Beginning in the late 1930’s and early 1940’s observations of nature showed us that there was more to evolution than anyone had previously anticipated. This was called the Modern Evolutionary Syntheses and it married natural selection, sexual selection, etc. to population genetics. What we now know as modern genetics (genes, genomes, RNA, DNA, etc.) has allowed us to become much more precise and accurate in our understanding of evolution.

Based on this better understanding of how nature works, an interpretation of “survival of the fittest” would have to be greatly modified. Where before we used a general, nonspecific term: “traits” we can now use a very specific term: genes. And where before we equated “fitness” to how well an individual was adapted to its environment, we now know that many factors influence an individual’s ability to survive and reproduce. Therefore “fitness” is more appropriately understood as a measure of an individual’s genetic influence over the next generation. The “fittest” are those individuals who get proportionally more of their genes into the next generation than others.

Our interpretation of “survival” would have to be greatly modified as well. This would no longer refer to an individual’s life, but to the continuation of a gene from generation to generation. For example those genes that cause a male spider to linger after mating may increase the likelihood of his death at the jaws of the female, but they may increase his fitness. How? There are pros and cons of staying and running away. A pro of staying is that the calories from his body may let the female produce more eggs. A pro of leaving is that he may be able to mate with another female. If, for a particular male, being eaten results in a greater number of offspring than attempting (and probably failing) to find another receptive mate, then his genes have “survived” even though he didn’t.

Today “survival of the fittest” has all but gone extinct among the scientists. They have no use for it. Just about the only groups that do use it misunderstand what evolution is, an explanation of how nature works, and pretend the phrase is an excuse to do bad. So if you run into someone who’s misusing this quip from history to malign a beautiful and fascinating part of our universe don’t be upset. Just look them straight in the eyes and say, “And you know what, that gravity is a crock too. ‘What goes up must come down,’ my ass!”

Author’s note:
“What goes up must come down” is not an accurate summary of gravity, there is no “up” in space and the sun, moon, and stars certainly aren’t coming “down”.