Swift Swallow Selection
Tail feathers set evolutionary hearts a flutter
By Carl Wieland
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Photo by A.Wilson,USGS
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The newspaper heading boldly crowed: ‘A case of dramatic evolution’.
The article, by New York Times columnist Carl Zimmer,1 concerned
what he said was ‘one of the biggest evolutionary shifts ever documented in
a living population of wild animals.’
So what caused all the flap? The Journal of Evolutionary Biology was about
to publish some 20 years of research by European scientists on barn swallows. The
males have two outer feathers on their tail, and these had become gradually longer,
by 10%—about 11 mm (½ inch)—on average. The length of the central tail
feathers had not changed in those two decades.
The researchers say that evidence suggests that female swallows are attracted by
the display of the outer tail feathers, not the others. So this may be a case of
sexual selection . If females prefer males with more of the genes for longer
outer tail feathers, then those genes will have a greater chance of predominating
in the population. So, on average, tails will become longer over time.
However, that will normally only be the case if there are already long–tail–feather
genes in a population—sexual selection, like natural selection, can select
only from what is already there.2 The same principle is illustrated for
fur length in dogs.3 And it will soon reach a limit, as selection of
any sort always does—see the box ‘Sweet limits’.
We have pointed out over and over that natural selection (an obvious fact that was
first described by creationist Edward Blyth4) creates nothing new; it
just ‘chooses’ from whatever is already on offer).5,6 Those
genes which don’t survive to the next generation (whether from the death of
the unfit in classic natural selection or from being rejected by ‘breeder’s
choice’ in artificial selection, or ignored by ‘mate choice’ in
sexual selection) are effectively being culled.
That is, selection can get rid of genetic information, but it can’t create
any. And since goo–to–you evolution requires a massive net increase
of information over time, that means that simply watching selection in action does
not demonstrate ‘evolution’ in action, no matter how much evolutionists
may attempt to ‘beat up’ the story.
It would be more impressive for evolutionary storytelling if it could be shown in
this case that mutations (inherited mistakes, ultimately the only possible source
for new information in the evolutionist’s toolbox) had introduced new genetic
information coding for longer feathers. But mutations are virtually always downhill,
i.e. a loss of information, including the rare beneficial mutations.7
And there is no suggestion in this research of mutations being involved at all,
nor is there any reason to think that anything other than simple selection from
existing genes is involved.
Interestingly, the Zimmer article makes reference to similar observations (which
we have written about8) concerning changing beak lengths of Galápagos
finches under the selection pressure of varying rainfall. That got evolutionists
excited, too, but in that case also there was no evidence of mutations or any other
source of new information. And, not surprisingly, when the rainfall changed back
to its previous pattern, the beak lengths shifted back again, too. Such shifting
back and forth around a mean under selection pressure is to be expected from simple
genetics. But, like the swallow tale, it is hardly anything to get excited about
in terms of demonstrating how microbes allegedly turned into microbiologists.
From where we stand, the faster the changes, the better.
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In fact, if anything, it is creationists who should be excited about the speed
of such changes. In the Creation/Fall/Flood/Dispersion model of Earth history, some
very substantial changes within the created kinds have happened in what, to evolutionists,
is an ultra–short time. The various beak lengths on the Galápagos have indeed
come from a single ancestral population, as Darwin envisaged (but not the old–earth
Bible–compromisers of Darwin’s day, who believed God had created all
species in their current spot, ignoring the Flood). Selection would have had a great
deal to do with this sort of adaptive radiation, and also the diversification of
many of the kinds on the Ark into a greater number of descendant species. Only it
would have had to happen in centuries, not tens of thousands of years.
So despite evolutionists (who are in any case often ignorant of what informed creationists
are claiming) wanting to rub our noses in this ‘tale of two feathers’, the
shoe is on the other foot. It is, as always, delightful whenever evolutionists report
changes under selection happening over a timeframe which, to them, is surprisingly
rapid.9 Keep the observations coming, guys. From where we stand, the
faster the changes, the better.
Sweet limits
After Darwin’s Origin of Species was published, sugar beet farmers
in France started to enthusiastically apply selection to increase the sugar content
of their crop. But once all the ‘high–sugar’ genes had been selected
into one line (leaving out others in the process) the sugar content reached a limit
which has not been surpassed since. All selection tends to similarly reach a limit,
because gene pools only have a certain amount of information for any particular
trait. And no creative evolutionary process exists to overcome that limit by adding
true novelty (see main text). It is conceivable that mutational damage might cause
loss of a control gene, thus transcending the limit for, say, sugar production,
but that, too, would be a loss of information. So it would not be the sort of process
needed to demonstrate how microbes are supposed to have turned into microbiologists.
FAST FACTS
- Barn swallows are the most common and widely distributed swallow species in the
world.
- Previously cave and cliff breeders, they now nest almost exclusively in artificial
structures.
- Unmated males may kill the young of a nesting pair, apparently to split up the parents
and secure the female for themselves.
- Barn swallows migrate in large groups; some North American ones winter as far away
as Argentina.
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References and notes
- Zimmer, C., A case of dramatic evolution, International Herald Tribune,
2 December 2004, <www.iht.com/articles/2004/12/01/healthscience/snbirds.html>.
- A mutational defect could conceivably damage control genes such that the feathers
grow longer than their ‘genetic limit’, though this would still involve
a loss of information and be a ‘downhill’ change. An extreme case of
this is shown in Lamb, A., The mutant
‘feather–duster’ budgie, Creation 24(1):54–55,
2001.
- See Sarfati, J., Refuting Evolution, Creation Ministries International—Australia,
Master Books, Arkansas, USA, p. 35, 1999–2004.
- See Grigg, R., Darwin’s
illegitimate brainchild: If you thought Darwin’s Origin was original,
think again! Creation 26(2):39–41, 2004.
- Wieland, C., Muddy Waters: Clarifying
the confusion about natural selection, Creation 23(3):26–29,
2001.
- Wieland, C., The evolution train’s
a–comin’ (Sorry, a–goin’—in the wrong direction),
Creation 24(2):16–19, March 2002.
- Wieland, C., Beetle bloopers:
Even a defect can be an advantage sometimes, Creation 19(3):30,
1997.
- Wieland, C., Review of The
Beak of the Finch: Evolution in Real Time by Jonathan Weiner, Journal of Creation
9(1):21–24, 1995.
- Catchpoole, D. and Wieland, C., Speedy species surprise: The rapid
appearance today, of new varieties of fish, lizards, and more defies evolutionary
expectations … but fits perfectly with the Bible, Creation 23(2):13–15,
2001.
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