2.3 What is NOT evolution?

Correcting common misconceptions

The term “evolution” is used both in scientific and everyday contexts. Our everyday usage can sometimes lead to incorrect assumptions about biological evolution. Here, we correct common misconceptions.

Evolution happens to populations, not to individual organisms. In everyday life, we often refer to people or ideas as having evolved. For example, we may remark that a soccer player’s style of play has evolved over their career. In biology, individual organisms do not evolve. An individual may change over its lifespan – for example, a human may be able to run faster – but this is not an evolutionary change. Evolution is a change in the frequency of a specific trait in a population over multiple generations. An example of this is when a new version of a gene called EPAS1 became more common in a population of Tibetans over time.

Evolution does not occur on demand. A brown-colored frog on a leafy green background may be quite visible to predators, and would likely benefit from a change that caused the frog to be green and thus concealed from danger. However, an individual frog cannot will itself or its offspring into becoming green.

Evolution cannot be stopped. Populations are always changing, for better and for worse. Biologists often speak of evolutionary change that involves a population-level increase of desirable features. For example, inland plants that colonize a coastal area may become more salt-tolerant in their new habitat. But sometimes, useful features are lost either due to random chance or fluctuating environmental conditions. For example, human ancestors could synthesize their own vitamin C, but modern humans cannot. The loss of this ability has led to thousands of human deaths from scurvy, a debilitating disease that results from insufficient levels of vitamin C.

Evolution does not produce perfection. A frog that blends into its background may have extra protection against predators, but is still susceptible to disease-causing parasites, drowning in a flash flood, or getting squished by a human foot. Just like animals who must consume other organisms because they cannot convert light energy into chemical energy, and humans who must consume certain foods for their necessary vitamin C, all organisms are biologically imperfect. Instead, we are the product of an evolutionary history that lacked foresight and evolutionary processes that could only work with the genes that already existed in the population. There are also physiological and molecular realities that mean that organisms cannot become perfect. For example, it’s simply not possible for humans to live forever or to produce thousands of offspring.