5 More Misconceptions About Natural Selection

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5 More Misconceptions About Natural Selection

Natural Selection is more than just survival of the fittest
Lioness at wild - hunting and watching. Getty/1001Slide

Charles Darwin and Alfred Russel Wallace first came up with the Theory of Evolution in the 1850s. Independently, these scientists came to the conclusion that the mechanism that drives evolution is natural selection. They described natural selection as the way way nature, or the environment, in which an individual was living would determine which adaptations the members of the species had would be beneficial. If an individual of that species had the preferred traits, it would live long enough to reproduce and pass down those characteristics to the offspring. Ideally, the undesirable traits would eventually disappear as those individuals that were least adapted to the environment would die off before they were able to reproduce and pass down those less suitable traits to the next generation.

Over time, the true meaning of the term “natural selection” has changed as people misunderstand its actual role in evolution and how it works. Below are some common misconceptions the general public has about the mechanism of natural selection.

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Natural Selection Causes Mutations

DNA mutations occur at random
A DNA molecule with a mutation. Getty/Marciej Frolow

Many people are confused as to the reality about how species change over time. It is a common misconception that in order for an individual to adapt or a species as a whole to adapt there must be some sort of mutation that happens. Therefore, it would make sense that natural selection is the cause of mutations in individuals or in species.

There are a couple of things wrong with the logic of that argument. First of all, mutations occur spontaneously or are caused by some sort of chemical or other type of mutagen. A process, like natural selection, cannot cause mutations. Secondly, it is important to remember that only species as a whole can evolve and not an individual. Even if a mutation happens spontaneously in an individual, that does not mean the individual has evolved. Natural selection, on the other hand, must have a variety of individuals to work on to dictate which is the preferred genetic code that should be passed down to the next generation so the species as a whole can live longer. That is the aim of natural selection and ultimately evolution.

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Only the Fittest Individuals Survive

Only cheetahs fit enough to catch their prey will survive
Cheetah chasing topi. Getty/Anup Shah

Once again, this misconception comes from the common use of “survival of the fittest” as a synonym for natural selection. It is much more accurate to say “survival of the fit enough”. Natural selection does weed out the undesirable traits, or at least reduces them significantly, but it's not only the organisms with the best adaptations that survive. Many others that have good, but not great, traits will also survive. This is why there is still variety in species instead of a uniform set of genetics.

In the end, this is actually a good thing. If only the fittest survived, then all future generations would have those same traits and no others. That means natural selection would have to stop working on that population because there would be no diversity in the traits for it to act upon. For instance, if a species of a certain type of tree had only one set of the “fittest” genetics in all of its individuals and then a disease that killed off these trees came along, there would be no way for the tree species to survive and it would go extinct. A diverse gene pool for species allows them to adapt when the environment changes.

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Natural Selection Always Improves a Species

Natural Selection doesn't always make a species stronger
Two men lifting weights in a gym. Getty/Paul Bradbury

This sort of branches off from the last misconception about only the absolute “fittest” surviving. Ideally, this would be the aim of natural selection and all undesirable traits would no longer be seen in a population. However, this is not the case. Again, diversity is still present in traits, but it may just be at a lower ratio of undesirable to desirable traits. This is necessary in order for a population to survive an environmental change. If an environment suddenly changes, it may make those traits that were the "fittest" according to natural selection no longer desirable.

Often, this misconception about how natural selection works is used as an argument against evolution by the anti-evolution crowd. The opponents will assert that natural selection, and subsequently evolution, cannot be real because there are still bad traits like genetic diseases that get passed down. They argue that if natural selection and evolution were true that there would be no diseases because they are clearly not the “fittest” and are a poor adaptation. This is an oversimplification of the facts and a misconception in and of itself. Knowing that not all bad traits do disappear and some will get passed down is one way to discredit this argument.

 

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Extreme Phenotypes Are Not Desirable

Natural Selection can favor extremes or the average
Three types of natural selection. Getty/Encyclopaedia Britannica/UIG

“Average” is such a tricky term to use. It generally means “middle of the road” or even to some it means “normal”. It seems logical that natural selection should choose the “average” or “middle of the road” trait as the desirable one over either extreme. Isn't that what “average” means? To find an average you add up everything and divide it evenly so average is the norm. This is not necessarily true with natural selection. It all depends on the environment.

Some environments do prefer the “average” and will undergo stabilizing selection. However, there are many others that prefer an extreme phenotype and will be under the influence of directional selection. There are even ecosystems and environments on Earth that actually prefer having both extremes over the average and those will be influenced bydisruptive selection. Each environment is different and can change at any time. Natural selection’s “preference” of one adaptation over another is entirely influenced by the environment and its own evolution.

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Species Can Just Adapt to Human Changes

Polar bears are endangered due to human interactions with the environment
Polar Bear on an ice floe in Norway. Getty/M G Therin Weise

This is perhaps the most dangerous misconception out there in some of the general public regarding how natural selection works. This stems from the idea that species of animals and plants can just adapt if their environment changes and they will survive. So it doesn't matter what humans do to change the environment, right? If we chop down rain forests, those species can either adapt to not live in the trees or they can move. If we contribute to global warming, species everywhere can just lose some of the fur or blubber and be fine through adaptations.

It doesn't work like that. If the traits are not already encoded somewhere in the DNA of the species, they cannot just adapt. It isn't like polar bears can just sprout gills and fins to become marine life as their ice caps melt. Unless there is some sort of drastic DNA mutation that happens by chance, species cannot adapt quickly enough to change as their environment changes so rapidly. This is how mass extinctions could happen. Natural selection changes as quickly as the environment does, but species, especially those that cannot produce new generations quickly, cannot.