In the previous post , I introduced what I consider to be two of the most pervasive misconceptions in evolution: that all evolution occurs via natural selection and that everything is an adaptation. Ready to bust a couple more?
Misconception #3: Evolution is not random/Evolution is random.
Correction: There are certainly non-random components to evolution—most notably the process of natural selection. Overall, however, evolution is neither entirely non-random nor entirely random. Mutation, which provides the raw variation upon which evolution can act, is a random process, at least in the following sense: organisms do not get the mutations they need to be successful. Rather, they get what they get and whether the mutations, once in place, have positive, negative, or neutral effects depend entirely on interactions with the environment. Mutations aren’t the only source of randomness in evolution. Genetic drift, a mechanism of evolution alongside natural selection, is random as are changes in the environment that influence natural selection.
A great, clear example of this system is the rock pocket mice in the American Southwest—mice populations living on dark volcanic rocks are almost entirely dark-colored, while mice living on adjacent sandy areas are almost all light-colored. The mutation responsible for the color variation was entirely random, but the stark phenotypic difference of the two populations is not at all random.
What this misconception looks and sounds like: The misconception about evolution’s non-randomness leads directly to teleological statements such as, “The rocks changed color, so the mice changed color, too” or “When black rocks formed, the mice needed to get darker, so they did.” The opposite misconception would sound something like, “No way the mice all turned black by chance—it’s too perfect!”
What to do about it: Fundamentally, it’s important to be explicit about the components of evolution that are random and the components of evolution that aren’t. When discussing natural selection, be sure to emphasize that while adaptations are beneficial in the current environment, there is no guarantee that will always be the case. If the environment changes, once-helpful traits may no longer confer any advantage. Dinosaurs were doing pretty darn well until that asteroid hit, for example! It’s also important to correct teleological statements. This can be very hard because they often sound so reasonable—of course, the rocks changed color so the mice needed to change color, too—but that’s wrong and it should be pointed out as wrong. Be prepared for students to push back on you, failing to see the difference between “dark fur evolved so the mice could avoid predators” and “dark fur enabled the mice to avoid predators,” but be persistent. Making the correction is critical to getting your students to break free of this misconception.
Misconception #4: Organisms that appear later in the history of life are somehow better or more advanced than those that evolved earlier.
Correction: Every type of organism around today has what it takes to survive in their environments—they are all “good enough,” not in any way better or worse than each other. Looking for the roots of this misconception takes you all the way back to ancient Greece and the scala naturae —the ladder of nature. Originally, the concept was used to show the relationship between the mortal and divine, but later on, it served as an organizing principle for the natural world: plants and invertebrates on the bottom, humans on top, everything else in between. But while it’s true that, for example, fish evolved before amphibians, it is not true that living fish are somehow simpler or less evolved than living amphibians. There is no way to make an unbiased assessment of how “advanced” or “progressive” an organism is—who is to say whether the glowing “fishing rod” of the anglerfish or the antifreeze proteins of a common wood frog is more evolved?
What this misconception looks and sounds like:
Students suffering from this misconception will often refer to certain organisms as “simpler” than others, as in “reptiles are simpler than mammals.” Even a statement such as “dinosaurs dominated until the age of mammals began” can be indicative of this type of ladder-of-life thinking.