Survival of the Fittest is A Misleading Phrase

Darwin’s (and Wallace’s) theory of natural selection, also known as evolution, is often summarized as “survival of the fittest.” This brings to mind various species competing for scarce resources and battling each other for survival. This is misleading and not how natural selection works; cutthroat competitive fitness is not a component of evolution. Rather than thinking of evolution as “survival of the fittest” Princeton biological anthropologist Alan Mann says we should think of evolution as “reproduction of the fittest.”

Reproduction of the Fittest

According to Dr. Mann, “Fitness refers not to how long an organism lives, but how successful it is at reproducing. And survival of the fittest fails to encompass the subtleties of natural selection.” Source. Slight differences in reproductive success is the primary mechanism behind evolution. According to Scientific American, “Natural selection simply means that those individuals with variations better suited to their environment leave behind more offspring than individuals that are less well adapted. This outcome is known as differential reproductive success.”

According to Andrew Lo of MIT,

Even very slight differences in reproductive success can lead to a genetic trait becoming common in an evolutionarily short amount of time, in the same way compound interest can turn a small amount of money into a small fortune over the years. A genetic trait that gives an individual a slight reproductive advantage in its environment—as little as 1 percent more offspring than individuals who lack that trait—will cause the gene variant for that trait to sweep through the population in an evolutionarily very short period: a few thousand or even a few hundred generations. In humans, this might be as short as a few thousand years.

For example, as I discussed in the IFOD The Mathematics of Evolution, a study of sandy vs. black colored mice in Maine showed that a relatively rare mutation (1 in 25 million) that caused a mouse to have black fur and a slight survival advantage (of 0.01) to that mutation will result in most of the population being black in just a few thousand years, and maybe much sooner if the initial population is bigger. This is a great example. These mice evolved to have black fur not because the sandy and black mice battled for survival. There was no cutthroat competition. Rather, black mice merely had slightly greater reproductive success and had additional offspring survive than the sandy mice.

It is not the fiercest or strongest organism that will necessarily survive. Sometimes, the weaker and slower organism has more reproductive success. For example, we humans have had ridiculous evolutionary success and as compared to other mammals we are relatively weak, slow, and without fur to protect us from the elements. Our success relates to our big brains and social cooperativeness. We didn’t battle and win. Rather, we developed key traits that led to reproductive success such as the ability to use tools, tell stories, have empathy, and work in groups.

Why This Matters

Evolution is a tough concept to wrap our heads around. To think that my dog (who is napping next to me) and I evolved from a common ancestor organism is mind-boggling. No wonder a majority of Americans don’t believe that evolution occurs without the guidance of a supernatural being. Part of the reason it’s so hard to believe in natural selection is that we misunderstand how it works. We don’t see species and individuals with different traits battling for survival so our flawed understanding of evolution doesn’t jive with what we observe. Maybe the idea that having a trait that confers a slight reproductive advantage is the true driver of evolution might be more palatable.

Here’s a recent IFOD related to evolution that I think is quite interesting: There is Grandeur in this View of Life