The
other day, I googled the best arguments used against creationism. No
worries, folks. They're mostly offering bald assertions, appeals
to authority, and straw men. Any way, I did find an interesting
graph. Actually, “interesting” is probably too strong a word.
It's more like amusing. At least it sparked my interest in
writing this post.
The
author was trying to make the point that little changes can
accumulate over time to create big changes. It's one of the Five
Lies that Evolutionists Tell. Evolutionists say that the only
difference between micro- and macroevolution is time and scale. By
the way, I discourage use of those terms; evolution doesn't happen at all –
neither micro nor macro. To make his point, the author showed how
you could change the word AARDVARK to BASEBALL by changing only one
letter at a time.
Now,
as a lover of using analogies, I can appreciate how difficult it is
to create a really good analogy. I normally wouldn't nitpick an
analogy if I can at least see the overarching point its author is
trying to make. However, in this case, there are such fundamental
flaws in the analogy that I believe it better illustrates some of the
difficulties of evolution rather than how evolution could progress.
Before
I get into the difficulties in the analogy (and, by extension, with
evolution), let me offer a thumbnail of what the author is trying to
demonstrate. Evolution supposedly happens via mutation and natural
selection. A mutation will occur in the DNA of an organism; on rare
occasions, the mutation will offer a benefit to the host; because of
this advantage, the host may live longer (natural selection) and
leave more offspring which will inherit the beneficial mutation;
eventually, the descendents with the beneficial mutation will replace
the entire population. In the analogy, the changes in the letters
represent mutations in the DNA. The accumulation of these changes
can turn the ancestral species into a different species in the same
way changing one letter at a time can turn AARDVARK into BASEBALL.
Did
I misrepresent anything? The we'll continue.
The
first problem is rather glaring. The steps in between AARDVARK and
BASEBALL are just groups of letters that don't even make words.
Going from words to meaningless letters represents a loss of
information. Why would natural selections select mutations that
don't gain anything?
For
evolution to happen, a mutation must make the host more fit for that
environment than before the mutation. For an arm to become a wing,
certainly there must be thousands of generations in between the fully
formed arm and the fully formed wing. Every step of the way, the
mutated limb had to be more beneficial than the generation before it.
It's hard to imagine a scenario where a limb that is not quite an
arm but not yet a wing will be selected over a functioning arm. To
imagine that it happened thousands of time is beyond incredible. Oh,
and by the way, we only have a handful of fossils alleged to be
transitional between a forelimb and wing. The thousands of in
between forms that must have existed apparently left no fossil
evidence showing the change.
Evolution
is impossible if any of the transitional forms between the starting
and ending species are one bit less fit than the generation before
it. They'd be like the meaningless words between AARDVARK and
BASEBALL.
The
second problem is that evolution is not a directed process. The
author of the graph knew he was heading toward BASEBALL and selected
only those letters that worked toward that goal. Natural selection
doesn't know that it's supposed to choose the limb that is more like
a wing; instead, it will only select the one that is a more fit arm.
Neither will it select the other features necessary for flight (like
hollow bones, intricate feathers, or perching legs) unless those
features offer some survival benefit to the earth-bound creature.
Natural selection will have the tendency only to make a terrestrial
creature a more fit terrestrial creature. It will not select
mutations that could eventually make an earth-bound creature a flying
creature.
The
final flaw I see in the analogy is the enormous room for error. For
the analogy to be realistic, all the steps in between the starting
and ending words should also be words. Here's an example with a
4-letter word, PLAY – FLAY – FLAG – FLOG – FROG. In this
case, every step in between is a real word. However, in each place
there are 26 possible replacements which means you are far more
likely to get a meaningless word than a real word. In the real word,
mutations are far more likely to be neutral or harmful than they are
to be beneficial. The harmful mutations in the DNA will far outpace
the beneficial mutations which means for every beneficial mutation
that a creature inherits, it will inherit thousands of unbeneficial
mutations. This is known as genetic burden.
In
1995, A.S. Kondrashov published a paper in the Journal
of Theoretical Biology where he discussed contamination of the
genome by very slightly deleterious mutations. Over time, the ratio
of harmful mutations to good mutations should become unbearable and
he says, “This
paradox cannot be resolved by invoking beneficial mutations or
environmental fluctuations.”
In the title, he asks, “Why
have we not died 100 times over?”
In
conclusion, the graph is not just an oversimplification - it's
deceitful. It presents evolution as a simple, stepwise process where
tiny, gradual changes and a whole lot of time could easily do what seems impossible. 1, 2, skip a
few, 99, 100!!
2 comments:
The steps in between AARDVARK and BASEBALL are just groups of letters that don't even make words.
But the genome isn't an English (or Japanese, or Amharic) text. If you change one amino acid in a protein, you still have a protein. The change may have effects ranging from drastic (and very probably harmful) to non-existent, but it's still a protein. Your analogy imposes a constraint that doesn't exist in the process it's analogous to.
The second problem is that evolution is not a directed process.
That cuts against your argument as well as for it. So what if you can't make the transition between "AARDVARK" and "BASEBALL?" Evolutionists are quite content that some evolutionary transitions are virtually impossible, perhaps absolutely so. We see some part of what was actually possible; evolution has no goals that it might fail to reach. An analogy with a fixed goal (and no alternate goals accepted) is unrealistic in that respect.
In the real word, mutations are far more likely to be neutral or harmful than they are to be beneficial.
Hence the importance of noting that evolution happens to populations; it is a process of massive testing in parallel. The same offspring doesn't have to experience every single mutation, and harmful mutations tend not to be inherited, at least not beyond a few generations.
Of course, this assumes that deleterious mutations are sufficiently harmful to significantly reduce an individual's chances of passing on his genes; your next argument deals with individuals that inherit a mix of beneficial and nearly neutral but slightly deleterious variants that started as mutations.
Over time, the ratio of [very slightly] harmful mutations to good mutations should become unbearable and [Kondrashov] says, “This paradox cannot be resolved by invoking beneficial mutations or environmental fluctuations.”
The summary of the article notes that it might be resolvable by "soft selection" (i.e. if natural selection, in effect, grades on a curve rather than eliminating every genome that falls below some fixed level of genetic quality) or by "synergistic epistasis" (genes having effects in combination different from their effects separately, or genes blocking the expression of other genes). In addition, since Kondrashov states that the effect depends on the size of the genome relative to the effective size (the number of individuals who actually reproduce, which is fewer than the actual number of individuals), the paradox might be ameliorated if the genome is smaller (as I recall, a widespread estimate at the time was that we had ca. 100,000 genes; the current estimate is roughly a fourth of that).
It's hard to imagine a scenario where a limb that is not quite an arm but not yet a wing will be selected over a functioning arm.
Take a look at Archaeopteryx. Beneath those flight feathers is the (lengthened, but otherwise entirely typical) forelimb of a maniraptoran theropod: fingered claws apparently quite capable of grasping. At least in birds, wings clearly remained functional as arms even after they became at least borderline functional as wings. As for other winged vertebrates, I recall that the same issue of National Geographic that carried a retraction of carried an article on gliding vertebrates of Madagascar: quiet a few of them survive despite having "half-formed wings" that have to do double duty as limbs and gliding wings. Actual specimens make up for the difficulty of imagination.
Oh, and by the way, we only have a handful of fossils alleged to be transitional between a forelimb and wing. The thousands of in between forms that must have existed apparently left no fossil evidence showing the change.
There are extinct species known from a single, perhaps fragmentary, fossil specimen. Presumably these individuals had parents, and probably siblings, and possibly offspring of their own that existed without leaving fossils -- at least none that we have found. And, regarding fragmentary fossils, it has been quipped (hyperbolically but not without reason) that mammalian paleontology of the Mesozoic consists of the study of teeth that apparently copulated with other teeth and produced baby teeth. Presumably in life those teeth were embedded in jaws and attached to limbs, spines, etc. but for many species, these have never been found. A lot of things that existed have left shockingly sparse fossil evidence -- but one doesn't assume that something didn't exist merely because one has only a few fossils of it.
I note in passing that the evolution of bird wings is harder to trace because few fossils retain any trace of skin covering (scales, hair, down, etc.). There are theropod fossils earlier than Archaeopteryx, for example, whose forelimbs can be rotated in the pattern of flapping flight (though their limbs are too short for this -- this is a case of having a feature, presumably for one function, that can be adapted to a new function with the addition of other traits, such as longer limbs). But their fossils show no trace of feathers (or anything else -- there's no particular reason to assume they didn't have some sort of feathers).
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