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First off, the props. This article is based on many books and journal articles I have read over the years as an evolutionary scientist. Although I have my own beliefs and sources, it is mostly inspired and influenced by a podcast by Zachary Moore called Evolution 101, from which I have taken quotes (italicized). Therefore, if you want more details on this subject and/or want to have a second opinion on the subject, feel free to refer to his podcast and blog. Also, feel free to ask me any questions about the article, and to let me know if some things you do not understand or if things do not seem to make any sense.
Seeing as the word evolution gets thrown around a lot lately on Newsvine, I wanted to make sure that we are clear about what the definition of evolution is. A lot of readers will be surprised to learn the simplicity of the definition and might actually modify their argument when debating against or in favor. Moreover, for the interested readers, I wanted to introduce some concepts of evolutionary theory and phylogenetics, and thus, I have decided to begin this series of articles on my field of specialization, evolutionary theory, and what better subject than "What is Evolution?".
1. A Proper Definition
A lot of the arguments on Newsvine, and in the news elsewhere for that matter, come from the fact that people do not know the proper definition of evolution. Even scientists!
Evolution is both a fact and a theory. A fact is an undeniable observation, like the fact that oil is denser than water, or the chemical reaction between two substances, etc. While the word theory represents a conceptual framework that we use to make sense of observations that we made.
So what do we mean when we say that Evolution is a fact ? Here are two perfectly scientific definitions of evolution:
- Definition 1.1:
- Evolution is the measurable change in the heritable traits (allele frequency) of a population over successive generations. -- Wikipedia
- Definition 1.2:
- In fact, evolution can be defined as any change in the frequency of alleles within a gene pool from one generation to the next. -- Helena Curtis and N. Sue Bornes, Biology 5th Ed.
For the readers who do not know what an allele is. It is any one of the many viable DNA codings of a gene. The most popular explanation uses the genes for the color of our eyes. Their exists alleles that code for blue eyes, brown eyes, etc. But, in general, only two alleles interact to determine the color of our eyes. I will not go into the details of how these alleles interact (maybe later if anybody is interested), but the idea is that evolution is simply the change in the allele frequency of a population. In this sense, it is a fact since we can observe the differences in the allele frequencies of a population over the generations by studying many species, like, for example, fruit flies or pea plants.
The role of evolutionary theory is to explain these changes in allele frequencies and make sense of those mysteries of science. One such theory was popularized by Charles Darwin in 1859, and it was based on something called natural selection, which is the process in which organisms with favorable traits are more likely to reproduce. Evolutionary theory is a scientific theory at the same level as gravitational theory, atomic theory, etc, and should not be doubted by the public. What is usually debated in public arenas is the actual origin of life, but so far we have not mentioned anything about the origins of life. This brings me to my next section.
2. What is NOT Evolution ?
In order to really understand the point of this article, it is important to contrasts definitions 1.1 and 1.2 with examples of what evolution is not. Here are two more definitions, taken from what should be reliable sources, which represents epitomal example of what evolution is not:
- Definition 2.1:
- The gradual process by which the present diversity of plant and animal life arose from the earliest and most primitive organisms, which is believed to have been continuing for the past 3000 million years. -- Oxford Concise Science Dictionary
- The development of a species, organism, or organ from its original or primitive state to its present or specialized state; phylogeny or ontogeny -- Webster's
- Definition 2.2:
These definitions are wrong in many aspects. First, they allude to the history of evolution rather than the actual fact of evolution. Using these, it would even be possible to debate whether evolution is still occurring. In definition 2.1, the use of gradual process should definitively be avoided since there are no facts proving that evolution is actually a gradual process. Actually, Stephen Jay Gould dedicated a large portion of his academic work on a theory called punctuated equilibrium, which was based on evolution occurring in steps, as an explanation of the fact of evolution. Moreover, definition 2.2 uses words such as primitive and specialized which should definitively be removed from their definitions.
It is extremely important, in your future debates, to remember that although evolutionary theory assumes that life arose at some point in time, it is unnecessary to the theory to posit a mechanism for how that life came into being. Therefore, creationism should not try to ridicule evolutionary theory since the debate on the origin of life should never be associated with evolution in the first place. Evolution is a theory of Biology -- the science that studies things that are alive, not things that become alive.
References:
- Helena Curtis and N. Sue Bornes, Biology, 5th Edition. 1989. Worth Publishers, p.974.
- Charles Darwin (1859). On the Origin of Species. London: John Murray.
- Eldredge, N. and S. J. Gould (1972) "Punctuated equilibria: an alternative to phyletic gradualism" In T.J.M. Schopf, ed., Models in Paleobiology. San Francisco: Freeman Cooper. pp. 82-115.
