A better definition of ‘evolution’?

Question

Occasionally on this site I’ve noticed the following definition of evolution being given:

Evolution is a change of allele frequency through time in a population

( For example, from here)

Recently the following (From here):

The statement "evolution is driven by mutations" is very misleading if not simply wrong. Just have a look at an intro course to evolutionary biology!

In short, evolution is a change of allele frequency over time.

But mutations are important to evolution, and I feel must be included in the definition.

Here’s why that concerns me: One group of evolution deniers, and others like them, use comments like these above to try and show a weakness in evolution.
See: http://creation.com/don-t-fall-for-the-bait-and-switch

With comments like:

“It is a bit of a trick played by using sloppy language. Evolutionists use adaptation, which is observed, to support evolution, which is an entirely different process. It is an example of bait and switch.”

Also:

“Next time someone says that evolution is an observed scientific fact make sure you get them to clearly define what they are talking about. They will almost certainly be referring to adaptation but want you to believe they have proved evolution. Don’t be fooled. Sloppy language leads to sloppy thinking.”

Ok, I hate to give them ‘air-time’ by posting that, but perhaps it will cause us to clarify ourselves better. Answers like "a change of allele frequency through time" just end up feeding right into this kind of evolution-denial.

SO, here’s my question Since there’s a lot people here smarter than me: Can someone please offer up a stronger definition of evolution than just ‘a change in allele frequency over time’?

In researching answers I found this on Berkeley’s site:

“Biological evolution, simply put, is descent with modification. This definition encompasses small-scale evolution (changes in gene frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations).”

I like that it goes beyond small-scale (which these others would just call adaptation). But this doesn't mention natural selection, and mutations; which I feel are important distinctions given the kind of comments these deniers make. Is there a reason Berkeley's definition didn't include those distinctions?

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EDIT: Can someone explain the down-vote? I followed everything outlined under How to ask a good question

Answer 1

The focus upon definition of term is a rhetorical strategy often employed to confuse the issue, especially by laity when discussing technical matters. Word meaning and use are easily a source of ambiguity, confusion, contradiction and such that the appeal to the dictionary definition is often an appeal to false authority. At the very least it is worth pointing out that aside from etymology and morphology, empirical disputes are not settled by consulting Merriam-Webster.

"Evolution" is a fairly general concept and it can be useful when discussing technicalities to specify "biological evolution". For example, "water" might mean specifically "H2O" or generally "clear, odorless, tasteless liquid" or possibly might be used without qualification in distinguishing "potable water" from ocean water, et cetera.

Consider that the definition of term is not so much the pertinent legacy of biological evolution (pace Darwin, Wallace et. alii). The kind of explanation biological evolution uses is it's hallmark. In particular, biological evolution removed teleology (the study of purpose)) from biology.

For example:

A teleological explanation of biology:
1) This plant is photosynthesizing in order to survive.
2) This plants species is surviving.

A biologically evolutionary explanation of species:
1) This plant is photosynthesizing
2) Plant species which photosynthesize have an increased likelihood of survival.

Note that survival is still at play, but the argument is no longer circular. This is not to say that cause has been cited, however, the logical structure of the argument no longer "begs the question"

Answer 2

This is the one I use for my intro to biology students.

"Biological evolution is a change in the number of times specific heritable characteristics(aka genes) occur within a population over time."

Keep in mind this is a description of the definition{law} of evolution not the theory of evolution. And is just a diffrent way of stating, "Evolution is a change of allele frequency through time in a population"

I use this becasue the possibility of evolution in machines, epigenetics, and xenobiology is discussed and students have a difficult time separating genes and nucleotide sequences, and not every student will know what allele frequency means.

defining evolution with natural selection would be pointless and circular, since natural selection is part of the theory that explains how and why evolution happens (but not the only mechanism by which it operates). We do not define gravity by the proposed mechanism but by the observed behavior of matter.

If mutation stopped tomorrow evolution would continue, It would not end until there was no life left to vary. So using mutation to define evolution would be false.

Deniers will deny no matter how you change the definition, there is no reason to bastardize the science to try to please them. You would be better spending your time discussing things like ring species or asking them to define "kind." Likewise speciation is the outcome and subset of evolution and completely covered in the existing definition. If they have a problem with speciation let them argue with it, speciation is only one form of evolution. If nothing else it will encourage them to learn something about what they argue.

Answer 3

I think that any definition that is useful for explaining evolution to laymen must contain the concept of natural selection. Here's my version:

Evolution is a gradual change in organisms over many generations caused by the combination of (1) random variation in genes among individuals and (2) the fact that those individuals that best survive and reproduce will transmit their genes to the next generation.${}^1$

That random variation arises (in part) from mutations is just a detail, in my mind. The fundamental mechanism, which is very hard to deny, is that even though variation in any individual's genes are completely random, the combination of this variation with survival of the fittest will produce a strong tendency to adapt to the environment. If someone has difficulty accepting / understanding this principle, it's easy to setup computer simulations that demonstrate the effect hands-on. In my experience this convinces pretty much everyone.

The "bait and switch" argument on the page you link to is fundamentally flawed because there is no difference between what they call "adaptation" and "evolution". Both are evolutionary processes, resulting from variation and natural selection. It's just that these creationists are willing to accept some consequences of evolution, but refuse to accept all of them. This is just a rhetorical device that lets them accuse scientists of "equivocation" (which sounds pretty sophisticated). Also, there are the usual falsehoods: "no intermediate forms", "mutations do not generate new information", and evolution is "just a hypothetical philosophy without observational scientific support".

But then again, creationist do not really care about the scientific arguments --- they only pretend to do so because they know science has credibility. They are driven by belief, and arguing with them is usually pointless.

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${}^1$ I am aware that this is not the most general definition one could give, as it does not encompass genetic drift and other mechanisms described by modern evolutionary theory. But I think it's an appropriate one for explaining evolution, as in the discussion brought up by the OP.