The
falsifiability of evolution is an important part of establishing
evolution as a scientific theory on the principles of
falsifiability.... A central characteristic of science is that it
must be falsifiable; this feature of a theory is attributed to Karl
Popper, who mentioned it in a criticism of Darwinism. Scientific
theories cannot be proven outright – they can only fail to be
disproven, and this means pointing out what evidence could disprove
the theory. If a theory cannot be disproven, such as with Russell's
Teapot, it makes no difference whether it is true either way.
Wow,
there's some bad grammar going on there. “Science” is the
methodology we use to study something. Surely they don't mean
“science” must be falsifiable. What they should say is that
“scientific theories” must be falsifiable. Yikes. Anyway, in
their own words, a good theory must be falsifiable. Am I
misrepresenting anything? Isn't that what they're saying? OK, then
on to my next point.
In
addition to falsifiability, another characteristic of a good theory
is that it must be predictive. A prediction is basically to
say that, if a theory is true, then we might expect a certain other
thing to be true. I might say, for example, that hair is unique to
mammals. If my theory is true, then I could predict that, if there
is hair on any creature we ever discover, it will be a mammal.
Predictions go hand in hand with falsifiability. If we ever
discovered a cold-blooded, egg-laying, gill-breathing creature with
hair, my theory would be proven false.
Let
me give you an analogy that might demonstrate how important these two
things are to a scientific theory. Suppose I wanted to mix paint to
make new colors. I would need to know which colors to mix to make
the color I want. If there were a “color theory” that predicted
yellow and blue together make green, then that's useful information
if I wanted to make green paint. If I mix yellow and blue paint and
actually get green paint, then I might use that theory to help me
with other color combinations. However, if the “color theory”
said yellow and blue could make green, red, or any other color, then
the theory isn't predictive and isn't useful to me at all.
Now
suppose the theory predicted yellow and blue would only make green,
but when I mixed yellow and blue, I got red. In that case, I would
know the theory doesn't make successful predictions. You could say
it has been falsified. The inventor of the “color theory”
might try to say that yellow and blue should make green but he can
“explain” why it made red. OK, but the next time I mix them, I
get brown. He then “explains” why I got brown. If he has an
explanation every time I don't get blue, then there's really no way
to falsify the theory. We're back to the problem that the theory
isn't predictive but neither is it falsifiable. It's a useless
theory.
That
the theory of evolution is neither predictive nor falsifiable is a
complaint often leveled against evolutionists. Creationists have
often asked for concrete examples ways to test the theory. What are
some specific, useful predictions that it makes and what are some
things that, if we found them, would falsify the theory? I've asked
this many times of many people and I usually get one of three
responses:
- A flat dismissal of my question, sometimes accompanied with elephant hurling – something like, “Evolution is the most tested theory in science and is supported by mountains of evidence!”
- A turn of the tables in an effort to put the creationist on the defense – that is, “Oh yeah, well how would you falsify creation?”
- On very rare occasions, someone will suggest something that they claim – if found – would disprove evolution.
It's
that last response that I'm most interested in yet it's the one that
I almost never hear. For whatever reason, evolutionists are
reluctant to enumerate concrete examples. I suspect it's because
they fear that if they commit to some hypothetical example, maybe
someday such a thing might someday be found.
The
RW article I linked above actually discusses a few examples of things
they claim could falsify evolution. I started writing a short
response to each point RW raised but my post started to get way too
long. Instead, I'm going to make a series. Check back soon for my
first response to the first two points.
Related
articles:
Read
this entire series:
I remember a couple of details from an experiment done in high school: two clear, colorless liquids (one contained lead), that mixed together, produced an opaque, bright yellow liquid. That blue and yellow pigment mixed together make green assumes that the pigments don't react with each other or the surface they're painted on; if you're using compounds that do react with each other, you may get some other color. It isn't that theories lack predictive power (note that "predictive power" and "falsifiability" are the same thing viewed from different angles); it's that the universe is a complicated place and that sometimes there are multiple causes (each with its own theory or explanation) at work.
ReplyDeleteHence the Quine-Duhem thesis: it is impossible to test hypotheses singly; they are always tested in bundles. If, e.g. we take J.B.S. Haldane's classic example, "a fossil rabbit in the Precambrian," we're testing the hypotheses "placental mammals didn't exist before basal amniotes," but also "these sediments are Precambrian," and "entire classes and phyla don't exist for millions of centuries without leaving fossils" (Henry Gee is especially fond of pointing out that you can't assume the earliest appearance of a taxon in the fossil record isn't necessarily the first time it existed, and its last appearance isn't necessarily a sign it went extinct).
This is a general principle about science, not just evolution: sometimes there is a perfectly good explanation, in terms of well-understood principles, for why you didn't get the result the theory predicted, besides "the theory is false." There aren't, in the real world, "silver bullet" falsifications that work invariably. In the real world, you need to deal with "consilience of induction" theories aren't proved or disproved by single cases but by multiple lines of converging evidence from multiple fields.
You don't mention any actual cases where, it seems to you, a prediction of evolutionary theory is falsified by data. Creationist debater Duane Gish had one: he asserted multiple times in debates that, e.g. human albumin was more similar to frog albumin than to chimpanzee albumin. This happened to be false (and he never corrected it), but certainly it would be contrary to evolutionary expectations. Likewise, finding that we shared endogenous retroviruses or pseudogenes with dogs or cows but not with chimpanzees or macaques would require rather drastic auxiliary hypotheses.
ReplyDeleteAnd frankly, pace Henry Gee's point about the deficiencies of the fossil record, finding a Precambrian rabbit, or even a Triassic mammoth (Walt Brown claimed to have found this, but he had mistaken Pleistocene for Triassic deposits, which sort of ruined the falsification) would be a major blow to evolutionary theory.
Note that Popper argued that natural selection as a mechanism for evolution was unfalsifiable; he never claimed that evolution itself was. There are obvious falsifiers (subject, always, to the Quine-Duhem problem) for common descent with modification over time; it's harder to see how one would test the hypotheses that non-random survival of random gene variants due to environment pressures caused, e.g. the enlargement of the brain in bipedal apes. Still, there are obvious falsfiers for natural selection, in general (e.g. if offspring don't vary, or if survival is random with respect to all variation -- creationists have argued the latter, but again, falsely), and there are subtler tests for natural selection as a historical cause, in some cases.
Steven J,
ReplyDeleteI think some of your questions will be addressed in my series but let me make a couple of quick points.
First, my paint analogy is meant to be overly simplistic. You're right that the universe is complicated but we have a pretty good handle on some things already. For example, we don't have to experiment to find out what would happen if I poked a balloon with a pin because we pretty much know already. I was just trying to think of a simple way to demonstrate how theories are used.
You're also right that theories and predictions are practically the same thing. If a theory predicts one thing should happen but something else happens, the theory has potentially been falsified. However, studying origins is a little different than most of science because we're trying to understand something that has already happened rather than what is happening or what will happen. If we find a fossil of some creature, we try to understand where it fits in the evolutionary scheme of things. We also use it to help flesh out our understanding of where and when things evolved. A case in point is our current understanding of human evolution. The current consensus is the “Out of Africa” scenario. However, if a human artifact were ever found in North America, dated by evolutionists to be 1,000,000 years old, it wouldn't falsify evolution. They would just have to rethink the Out of Africa story to allow humans reaching North America 900,000+ years earlier.
This highlights my frustration with evolution as a “theory.” I could show you literally hundreds of headlines that say something like, “New discovery changes our understanding of evolution.” I've linked to dozens of these types of articles on my blog already. While they're constantly writing and rewriting the theory of common descent, I'm asking what kind of discovery would it take to make them reject common descent all together? That's the whole point of this series. Sometimes people have to change their minds about where and when something evolved but nothing can cause them to doubt THAT it evolved!
Thanks for your comments. God bless!!
RKBentley