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Is Evolution Scientific?

This question isn't as simple as it sounds, but the short answer is yes, evolution is science. Evolution meets the criteria generally accepted by scientists as defining science, and the vast majority of scientists accept evolution as science.

Let's first list the basic criteria necessary for a theory to qualify as scientific:

• Consistent (internally and externally)
• Parsimonious (sparing in proposed entities or explanations)
• Useful (describes and explains observed phenomena)
• Empirically Testable & Falsifiable
• Based upon Controlled, Repeated Experiments
• Correctable & Dynamic (changes are made as new data is discovered)
• Progressive (achieves all that previous theories have and more)
• Tentative (admits that it might not be correct rather than asserting certainty)

Is evolution consistent?
Yes, evolution is internally consistent. While there are holes and disagreements as to how evolution occurred and there are some gaps in the evidence for evolution, the idea of common descent is still overwhelmingly supported by the evidence and the basic understanding of how changes take place in living organisms. Evolution is also externally consistent because, contrary to the claims of some, it does not contradict solid findings in any of the other physical sciences.

Is evolution parsimonious?
Yes, evolution it is completely naturalistic and does not add unnecessary concepts. Evolution as simply the genetic changes over time does not rely upon any entities or concepts which do not otherwise exist in science. Evolution as common descent also does not require us to imagine anything new or unusual to add to the universe. So far, the theory of evolution is the simplest and most reliable explanation of the current diversity of life on our planet.

Is evolution useful?
Yes, the theory evolution is very useful. It is the unifying principle of the life sciences, which includes medicine - this means that much of what is done in the medical sciences could not occur without the background premise of evolution. Evolutionary theory also suggests lots of problems for scientists to work on and it provides an overall paradigm for solving current problems within the life sciences.

Can the theory of evolution be tested?
Evolution, when addressing common descent, is largely a historical science. This means that it relates to actions that are supposed to have happened in the distant past, and this makes testing the theory complicated because, unless time travel is invented, we cannot directly test the theory.

However, this does not mean that the theory is not testable at all. As with other historical investigations, you can make predictions and retrodictions (to utilize present information or ideas to infer or explain a past event or state of affairs - e.g., to "retrodict past eclipses" as opposed to predicting future eclipses) based on the theory.

What this means is that we can state that we would expect to find certain things (say, certain types of fossils) when looking at the historical record, and if those things are found, it supports the theory. Thus, while we cannot perform the kind of direct tests like we can in physics and chemistry, the general theory of evolution is testable just as other historical theories are testable.

Can the theory of evolution be falsified?
Falsification of evolution as common descent would be complicated because of the vast amount of supporting evidence for it. The idea of common descent does not rest on one simple idea or single piece of evidence, so to falsify it would require some very significant findings rather than a single bit of anomalous data.

For instance, while finding one fossil in rocks that are much older than would be expected (say, a primate in Precambrian rock) would be improbable, it would be a stretch to say it would falsify evolution. Realistically, one anomaly against all the evidence would be a hard sell, and to be honest, while it would certainly raise issues (and creationists would have a field day), it would probably be chalked up to unknown error.

On the other hand, if a general pattern of finding fossils in rocks reliably dated to much different ages than expected was seen, that would deal a serious blow to the idea of common descent. One possible example of this might be if primate or mammal fossils started consistently turning up in Precambrian rocks - in such a situation, evolution would be in trouble.

What is important to understand here is that evolution rests upon a general and widespread pattern of evidence from a number of different fields. Because of that, a similarly general pattern of contradictory evidence would be required to falsify evolution. Isolated anomalies might at most force a modification of evolutionary theory, but they wouldn't cause it to be dismissed.

Another possible manner in which evolution might be falsified is if our understanding of physics and chemistry changed such that the laws and tests used for determining the age of the earth were found to be incorrect, and new tests showed that the earth was quite young, perhaps on the order of several thousand years. In such an event, the principle of common descent which is the basis of evolutionary theory would be dealt a fatal blow. There are also other any number of other ways in which evolution could be falsified, so there are ways in which the idea of common descent could be invalidated.

Is evolutionary theory correctable and dynamic?
Yes, evolution is dynamic and it is also correctable because it is based solely on the evidence. If the evidence changes so will the theory - as a matter of fact, subtle changes to aspects of evolutionary theory can be observed by anyone who regularly reads biology journals and pays attention to the scientific debates.

Is evolutionary theory progressive?
The idea that a scientific theory should be "progressive" means that a new scientific theory should build on the scientific theories that came before it. In other words, a new theory must explain what previous theories explained at least as well as they while providing a new understanding for additional material - something which evolution certainly does.

Another way to understand how scientific theories need to be progressive is that they can be shown to be superior to competing theories. Thus, it should be possible to compare several explanations for the same phenomena and find that one does a much better job than the others. Some creationists try to argue that evolution is a "religion" because scientists never consider any possible alternatives, but this is certainly untrue. Figure 1 graphically shows what the basic ideas about origins of life look like.

Competing Theories

A major "competitor" for Darwinian evolution was a theory by Jean-Baptist Lamark published in his Philosophie Zoologique (1809). This theory is usually called transformationism. Transformationism proposes that species originated independently (not via common ancestry) but can and have changed significantly since their creation. Lamark's mechanism of evolution is frequently referred to as Lamarkism and has since been discredited, in large part because it is simply not supported by the data.

The general theory of evolution does quite well at meeting the criteria for scientific theories. How about the scientific method: was the idea of common descent arrived at scientifically? Yes - the idea was arrived at by examining nature. Looking at existing species, examining their characteristics and commonalities, and considering how they arose led to the idea of common descent. What's more, that idea is and has been tested repeatedly. So, the general theory was arrived at using the scientific method.

The general theory of evolution was arrived at using the scientific method and it meets the criteria for scientific theories. Yes, evolution is science and it is scientific.