1.8.4 Microevolution and Macroevolution

Microevolution and Macroevolution

Within the subject of biological evolution, the terms “microevolution” and “macroevolution” are used. Microevolution is used to refer to those small changes that occur over generations, generally within a given species or sub-species. Macroevolution usually refers to the large-scale changes between major groups, such as plants and animals, amphibians and mammals, etc.

It used to be believed that since God created all things to reproduce “after their kind,” all species must remain unchanged after their appearance on the earth. This idea was based on the philosophies of Plato and Aristotle, and the work of Carolus Linnaeus in the 18th century. Linnaeus was the one who provided the basis for biological classification into such groupings as kingdom, phylum, class, order, family, genus, and species.

It is now well accepted even by most creation scientists that organisms do undergo genetic mutation, adaptation, and speciation (dividing into new species or sub-species). These kinds of changes can actually be observed over relatively short periods of time. However, most creation science advocates hold that such changes are limited to the species level, or to a more vague grouping of a Biblical “kind” that possibly includes the scientific classification of genus, or even “family.” Sometimes they will use another term such as “adaptation” to avoid the dreaded “E” word.

One of the problems with creation scientists saying that “microevolution within kinds has occurred, but macroevolution hasn’t” is the fact that their categories of “kinds” are not well defined. They may allow in some cases that a “kind” includes genus as well as species. Thus, “microevolution” within a “kind” might take in quite a lot of biological change, and yet must necessarily fall short of being macroevolution, because they have created their own unique definitions to be mutually exclusive. What it seems to come down to for many creation science advocates is that “microevolution is any sort of biological evolution that I am willing to accept, and macroevolution is any evolution that I am unwilling to accept.”

Macroevolution, or changes from one major group of organisms to another, is much more difficult to observe directly, because it presumably takes vastly longer periods of time to accomplish. Much of the evidence for macroevolution comes from comparison of fossil evidence of growing diversity of species over time, and the observable features and genetic relatedness between various groups of organisms. One of the really bad arguments made by creation scientists involves a confusion or distortion over what macroevolution really means. Caricatures or cartoons of hippos giving birth to whales may be comical, but as an attack on the scientific arguments for macroevolution, they fall far short. Scientists don’t believe, for instance, that some crocodile gave birth to the first bird. Rather, they say that reptiles and birds share a “common ancestor” at approximately some geological epoch, and that successive changes brought about diversity between the two lineages until distinct species developed.

Scientists in the field of biology, if they do use the distinction of micro- and macroevolution, generally believe that they are part of the same thing, and that there is no clear distinction between micro- and macroevolution. They observe that small changes occur within the species. They observe evidence for one species dividing into two distinct species, which can no longer mate with each other. They see other evidences of change over time in physical characteristics, genetics, and fossil progression through the geological record, and they conclude that macroevolution is simply microevolution that has been at work for a very long time. Some of these issues will be discussed later, but suffice it to say there are evidences for macroevolution having actually occurred (see “29+ Evidences for Macroevolution”, by Douglas Theobald). Whether such evidence is convincing or the conclusions are justified is certainly a matter for debate.