Microevolution and macroevolution are two terms used to describe two related phenomena within the field of evolution. A distinction is often made between microevolution and macroevolution for the purpose of bolstering the argument of creationism, in the attempt to point out a perceived “leap of faith” in the argument of evolution. It is arguable whether there should even be a distinction between microevolution and macroevolution, or whether the terms are used simply as a way of obfuscating evolutionary theory.

Microevolution is the process by which small changes happen within a species through the process of evolution. These changes might be caused by humans — such as the intentional breeding of different types of dogs into new breeds, or cross-cultivating some plants to bring out specific attributes — or they might be the result of natural selection. One of the most common examples of microevolution is the peppered moth in England during the Industrial Revolution, which over the course of a number of generations changed its coloring to better blend in with the soot-covered environment. Creationists accept the premise of microevolution — indeed, given that evidence is everywhere, and evolution may be observed over the course of a human lifetime, it would be difficult not to. The reason that many creationists find the distinction between microevolution and macroevolution useful is because it allows them to accept the existence of a phenomenon for which there is overwhelming evidence — microevolution — while shrugging off the phenomenon of macroevolution as preposterous.

Macroevolution is evolution that ultimately transcends the species barrier, yielding new species through a most likely gradual process of what could be termed microevolutionary changes. Macroevolution encompasses changes along the entire spectrum of life, from single-celled organisms all the way to conscious human beings. The evolution of humans from more primitive apes, of whales from land-dwelling mammals, and of complex vertebrates from worms are all examples of macroevolution.

The common creationist argument citing the difference between microevolution and macroevolution holds that, although microevolution is clearly observable, macroevolution is not observable, and therefore requires a leap of faith. Virtually all scientists, however, agree on the existence of macroevolutionary processes — although they might argue about the actual processes themselves — and most would say that the distinction between microevolution and macroevolution is a fabricated one. In the most common theories of evolution, macroevolution is simply a large collection of microevolutionary changes that accumulate over time to the point at which they cause speciation.

Somewhat ironically, the terms microevolution and macroevolution were coined by an evolutionary biologist in the 1930s, who found himself forced to concede that the two processes were equivalent. Although microevolution and macroevolution are still sometimes discussed in the scientific world, their meanings in this context indicate a difference of scale, rather than a fundamentally different process. Many scientists avoid the terms because they are perceived to have been co-opted by creationists, and some scientists might quip that the only difference between microevolution and macroevolution is a vowel.