What is fact without theory?

If there is any phrase that is sure to raise the hackles of an evolutionary biologist, it is that evolution is "just a theory." This rallying cry of creationists plays off of the public misuse of the term "theory" to mean "Any wild guess that comes to mind which doesn't have substantial evidence to be taken as fact." Issac Asimov put this more humorously in his essay "The 'Threat' of Creationism" (1981) when he wrote;

Creationists frequently stress the fact that evolution is "only a theory," giving the impression that a theory is an idle guess. A scientist, one gathers, arising one morning with nothing particular to do, decided that perhaps the moon is made of Roquefort cheese and instantly advances the Roquefort-cheese theory.

In contrast, a theory in science is a framework that helps to explain observations, data, and facts gathered about the natural world and has been found to be consistently accurate in such descriptions and predictions. Over the course of time theories might be modified or subsumed into larger theories in order to better explain nature, but given the tentative nature of science such flexibility is a strength, not a weakness. I'm sure that most readers are already rolling their eyes in boredom, the status of "theory" being well-known by those familiar with science and how it proceeds, but evolution presents us with a bit of a taxonomic problem. "The theory of evolution" is perhaps the most popular phrase, although others would rather us call it the "law of evolution" in order to subdue confusion over the word "theory." Yet others see no need to attach the term "law" or "theory" to "evolution" just as we don't refer to "the theory of gravity," instead attaching "theory" to natural selection, sexual selection, kin selection, etc. as those are all theories that help explain the fact of evolution. Given this diversity of opinion, how can we best reconcile the aspects of both fact and theory that are essential to understanding evolution?

In 1861, Charles Darwin wrote to Henry Fawcett about the importance of hypotheses in the study of the natural world. Darwin wrote;

About thirty years ago there was much talk that geologists ought only to observe and not theorise; and I well remember some one saying that at this rate a man might as well go into a gravel-pit and count the pebbles and describe the colours. How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service!

While data collection and observation could go on indefinitely, raw numbers by themselves does little more than present us with (to borrow Darwin's example) how many red pebbles might be in a particular quarry. To extend this example to a fossil site that I have some firsthand experience with, in Sewell, NJ there is a marl pit that yields fossil crocodiles, mosasaurs, bivalves, fish, birds, and dinosaurs at one level, sponges and shark teeth higher up, and fossil wood higher still. Such finds could be mapped out and be easily fit into the varying stratigraphic levels, but if we were to stop our train of thought there we would likely miss out on the bigger picture; that this site records the existence of a Cretaceous sea that covered this site which eventually shallowed and receded, the faunal changes reflecting the changes of habitat. This knowledge then allows us to predict what we might find in similar deposits of the same age elsewhere in the state, finds in other marl pits confirming this proposed ecological succession. If we were barred from attempting to explain this information, however, we were merely be left with a map of fossil finds, our efforts being little more than stamp-collecting.

Such notions might seem fairly straightforward in the consideration of biostratigraphy and ecological succession in the fossil record, but how do they apply to evolution? It should first be recognized that Darwin did not formulate "the theory of evolution" but instead "the theory of evolution by natural selection." Evolution, or "transmutation" as it was sometimes called, long preceded Charles Darwin, the major difficulty being that there did not seem to be an accurate mechanism to explain how creatures could change over the course of time. What Darwin was able to discern (and what came to A.R. Wallace in a fevered dream about the same time) was what we now know as the theory of natural selection, animals being born with variations that may be favored or acted against allowing animals with advantageous variations to survive and be more prolific, eventually changing in form over many generations. Males of a population of the Blue Moon Butterfly (Hypolimnas bolina), for example, were nearly wiped about by Wolbachia bacteria, 99% of the males succumbing to the infection. The remaining 1%, however, had a variation that made them resistant to the bacteria and allowed them to mate with the larger population of females, and by 2005 the male/female ratio was back to almost 1:1 with the males carrying the variation that provided their forebears with immunity. This is just one example of natural selection at work, the overwhelming weight of the evidence showing that it fully deserves the designation of "theory" in the scientific sense.

Evolution is not merely natural selection, however, and there are many more theories and hypotheses that factor in to how life changes through time. Stephen Jay Gould addressed this in his essay "Evolution as Fact and Theory" (1994), noting that evolution is a fact explained by many theories, but even if Darwin's theory of natural selection was somehow overturned or fully refuted it would not change the fact that Homo sapiens shared a common ancestor with chimpanzees over 6 million years ago and evolved in Africa. Gould wrote;

[E]volution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts. Facts do not go away when scientists debate rival theories to explain them. Einstein's theory of gravitation replaced Newton's, but apples did not suspend themselves in mid-air, pending the outcome. And humans evolved from apelike ancestors whether they did so by Darwin's proposed mechanism or by some other, yet to be discovered.

Creationists, by contrast, do not even base their argument on facts; their rationale is based entirely on dogma and comes up entirely short in terms of physical evidence. There is no actual evidence that Adam and Eve or the Garden of Eden ever existed, and the immense weight of the collected facts show beyond doubt that our species arose from apes, and while details of our evolution might be disputed there is no evidence that our species was created of dust and a borrowed rib. As I noted earlier as well, evolution has a predictive power entirely lacking in creationism (and the creationist "Trojan Horse" intelligent design). The fossil fish Tiktaalik rosae was discovered as paleontologists were able to predict where an animal might be found in rocks of an age when fish were giving rise to the first tetrapods by marrying what we know about geology with evolution. Creationism can make no such predictions. Intelligent design, which largely ignores paleontology and many other important scientific disciplines that contribute to evolution, also cannot predict where to look for supernatural intervention in nature, which is not surprising given that ID advocates constantly and consistently lie about who they think the intelligent designer is in a feeble attempt to distance themselves from young earth creationists. Simply put, the fact of evolution cannot be denied, even when various theories about how life evolves continue to be debated and discussed.

As Larry Moran points out in his recent essay "Evolution is a Fact and a Theory," though, there are some who will object to using the term "fact" or stating that it is certain that Homo sapiens evolved from African ape ancestors. In terms of philosophy, it might not be able to be 100% sure of anything, even that you and I actually exist (we may just be dreams of some slumbering giant), but we should not get bogged down into a hypothetical muddle of notions that there is no evidence for and cannot be confirmed or refuted. Still, let's say that there is 0.01% probability that we did not evolve; should we say that evolution is not a fact? Certainly not, as the fact that life has evolved (and continues to do so) is as certain as we can possibly get, and I am perfectly comfortable with calling it a fact despite the pleas of some who claim that such "liberal" usage of the term fact is dogmatic.

Evolution, then, doesn't necessarily require the prefix "theory of" in order for it to make sense. The phrase "theory of evolution" may be used with a little license to convey that there is a large body of knowledge and various interconnected ideas that confirm the fact that evolution has occurred, but for my own part I'm typically more comfortable calling frameworks like kin selection a theory being that it is one set of well-supported ideas that help explain the fact of evolution. Indeed, using the phrase "theory of evolution," can also cause confusion among those who have no gripe with evolution as a fact, Clive Thompson suggesting that we start using the phrase "law of evolution" in order to make our point more clear. This idea implies that there is a sliding scale of certainty that ideas rise up as they develop, a law being more powerful and prestigious than a theory. This line of reasoning falls into the same trap as the "just a theory" idea, though, and would do nothing except further obfuscate evolution and science in general. As other bloggers noted when the article first came out, a law is a fairly narrow and exact piece of knowledge, an example being the ideal gas law PV=nRT. A theory, as John Wilkins has noted, is broader and can be more flexible, especially in terms of biological theories where conditions and evolutionary pressures on a bacteria are not the same as those that would affect, say, a dinosaur.

I will agree with Clive Thompson on one point, though; much of the misunderstanding about evolution (and the focus of many school board meetings in conservative districts) deals with the misunderstanding of what a theory is, what a fact is, and how to tell the difference between them. In recognizing this problem, though, we shouldn't simply play word games in an attempt to make people say "Oh, it's the LAW of evolution? I have no problem with it, then." As Stephen Jay Gould notes in the essay I cited above, the larger problem seems to be that evolution is being neglected if not altogether ignored in classrooms, even when creationists are not actively pushing to slap warning stickers on textbooks. The fact that life evolved is beyond question at this point, Charles Darwin and A.R. Wallace almost simultaneously having devised a theory that accurately and effectively helped to explain the means by which life changes (although it is not the only one), and insisting that evolution is merely a "theory" directly runs counter to the truth of the matter.

T. Ryan Gregory addresses this issue in more detail and adeptness than I can in his new paper "Evolution as Fact, Theory, and Path," but in looking over many of the articles, essays, and blog posts on this topic it is difficult not to notice that scientists have been explaining evolution as fact and theory for years. Each has their own style, but in the end they are all making the same point that has yet to be fully understood by the public at large. As T. Ryan Gregory notes in the introduction to his new paper, it is a shame that the words "theory" and "fact" are often viewed as being in opposition to those unfamiliar with science, although it it would be difficult for scientists to be more clear about what each means in terms of evolution. For my own part, I think this problem is but a larger symptom of public misunderstanding of science, the "common sense" version of what a scientist is, what they do, and how they do it being little more than a caricature. Still, even if we were to remedy this image problem, there would seemingly always be opposition who believe that they have a book of "facts" (or at least that their particular interpretation represents "truth") and that anything that runs counter to their beliefs is unquestionably wrong. In the end, it seems that the fact of evolution is beautifully simplistic and easy to grasp while the theories require much mental investment and are still being debated, and it's this seeming disparity that many non-scientists find difficult to understand or reconcile.

Further Reading;

Pharyngula - Jebus, no... what a miserable idea.

Evolving Thoughts - Law, Theory, or Something Else?

Clive Thompson - "Why Science Will Triumph Only When Theory Becomes Law" (Wired)

Issac Asmiov - "The 'Threat' of Creationism"

Richard Lenski - "Evolution: Fact and Theory"

James Hofmann and Bruce Weber - "The Fact of Evolution: Implications for Science Education"

Larry Moran - "Evolution is a Fact and a Theory"

Stephen Jay Gould - "Evolution as Fact and Theory"

T. Ryan Gregory - "Evolution as Fact, Theory, and Path"

Mike Haubrich - "Gould on Dennett and Dawkins"