More sophisticated creationists try to wrap this idea into slightly more reasonable sounding language. They make a distinction between experimental science and historical science, arguing that only the first is real science because its experiments can be reproduced at any time. Evolutionary biology, they say, is a historical undertaking and thus much more open to interpretation.
Now obviously this argumentation is completely idiotic anyway. We can infer things about the past, we can infer to the best explanation, and we can reproducibly test hypotheses. For what is perhaps the simplest example, every time a palaeontologist fails to find fossils of mammals before the first fossils of marine fish, they provide a little more support for evolution and against special creation because under the latter "theory" one would expect fossils of all lineages to co-occur together right from the earliest strata.
However, it is always best to have a pithy analogy in these situations. At least I strongly believe that a good mental picture is worth a thousand carefully weighted words (which is why I crafted this recent post, for example). And for this historical versus experimental silliness, for this "have you seen evolution happen" idiocy, a commenter at Jerry Coyne's WEIT website has just given the perfect analogy:
Becca Stareyes: I’ve also never seen an acorn grow into a giant oak tree, or a baby boy grow into an old man, but I would look pretty darn silly if I implied such things should be treated with skepticism. Because between my personal observations of human and tree growth and aging, and less-direct evidence, it becomes pretty damn obvious what’s going on.This is definitely worth making a mental note of; the acorn example is beautiful in its simplicity, much easier to visualize and much better at showing the absurdity than an analogy using archaeology, for example. As a bonus, there is a reply poking fun at the infamous question "if humans evolved from monkeys, why are there still monkeys".
Rob: If acorns are trees why are there still acorns? Checkmate atheists!That one could, of course, also be addressed by asking back "if you are descended from your mother, why does your mother still live?"