Teaching Students a More Precise Definition of Evolution

Geneticist Theodosius Dobzhansky famously stated that “nothing in biology makes sense except in the light of evolution.” Biochemical processes, aspects of anatomy and physiology, ecological relationships, and more can be explained and understood better by understanding the underlying process of evolution.

Unfortunately, despite its importance, research has shown that “public acceptance of evolution in America is a long-lasting problem.” While the proportion of Americans who accept the concept has increased in recent years, it still remains relatively low at barely over 50 percent. In addition, there is a concerning wide range of misconceptions that are held by students regarding the topic.

Problems with ‘Change Over Time’

For a topic that is the underpinning concept of all of biology, it is essential that it be taught well and with care. If you ask a random student who has taken a life science course what evolution is, chances are they will respond with “change over time.” Many teachers throughout the world, published curricula, and even some state standards and assessments all use this precise phrasing.

It’s one of the quick and easy definitions, like “educated guess” for a hypothesis, that are used frequently because they simplify the concept enough to make it easy to remember. The propensity of students I teach to remember this definition years after taking biology shows how well the definition has accomplished this goal.

This definition is likely the most common way to teach evolution in the country and has been for a long time. Many teachers approach teaching evolution using the same definition that they were taught, or that is in their curriculum, but this can lead to misunderstandings among students. I have found that certain common misconceptions, particularly the idea that individuals can evolve, seem to be strengthened by this oversimplified definition.

When many people think of evolution, they think of it as that simplified concept of something changing over time, often visualizing something akin to the cover of an Animorphs book, which is how the word is now used in the vernacular. When a politician changes their opinion on something, it might be described as “evolving” on the subject. There are many diagrams and articles about how certain companies or logos have evolved (here is one such example). In Pokémon, a single wooper turning into quagsire is described as evolving, despite its being a process more similar to metamorphosis.

All of these examples describe an individual changing over time, which fits the definition that many students know. I once witnessed a student describe the formation of the Grand Canyon as evidence of evolution because we know how it changed over time. There are risks that come with pushing the memorization of this definition.

Individuals cannot and do not evolve. Many students, particularly younger students or those in lower-level courses, would struggle to know what it meant if they memorized Darwin’s definition of “descent with modification.” Simplifying the definition to “change over time” has helped students to remember a way to define evolution, but it is oversimplified to the point that it could be causing damage to students’ long-term understanding of the concept. I believe that to better combat some rampant misconceptions, we need to modify how we teach evolution.

Evolution is the change in genotype of a population over generations. Two of the key aspects of evolution that help foster the understanding that individuals do not evolve are that it affects populations and that it works at the generational level. If these are incorporated into our simpler definition, it would not be much more difficult to remember, but it could solve the issues that are introduced by “change over time.”

A Simple Alternative

A more precise definition is “evolution is the change of a population over generations.”

• “Population” will help students understand that individuals are not what evolve.
• In addition, “population” implies that it is living things that evolve and not just anything that changes over time, as seen with the Grand Canyon example mentioned above.
• By specifying that the process occurs over generations, the definition further emphasizes that it isn’t individuals that evolve. The definition also helps fight the misconception that evolution only involves speciation, the origin of new species—a small change from one generation to the next is still evolution.
• While this definition does not include the important aspect that it is the gene frequencies that change (which could be added for older students), the fact that evolution occurs over generations does help to work in the aspect that the differences are heritable. This can easily open up the discussion to gene frequencies in high school classes.

I believe the above definition to be much stronger, while still remaining simple enough for students to remember easily. Everything in biology is explained by the process of evolution, and by deepening student understanding of evolution, we increase their potential to learn other concepts at a deep level. If the way we are teaching it is doing students a disservice and hindering their understanding, then our definition needs to change over time.