googlef87758e9b6df9bec.html A Sure Word: I'd say their theory is bird-brained but birds are smarter than that.

Tuesday, June 2, 2015

I'd say their theory is bird-brained but birds are smarter than that.

From a Scientific American article:

Darwin concluded that color differences between sexes in birds... result largely from female preference for bright colors in males. This general rule has received much support since Darwin's time, but other influences have also been noted. For example, females of species that are exposed to predators while incubating tend to have dull colors.

Sometimes I'm fascinated with how evolutionists' minds work. Secular scientists claim they go wherever the evidence leads. In practice, though, they only go where evolution can lead them. As we study birds, for example, they don't ask, “Why are some birds brightly plumed?” Instead they ask, “Why did bright plumage evolve?” Evolution is the paradigm through which they interpret the evidence. Therefore, their conclusions will always seem to support evolution. It's a vicious, circular argument.

Let's consider the quote from Scientific American. Their point is that bright feathers in male birds evolved because female birds are attracted to the bright feathers (known as sexual selection). At the same time, female birds have drab plumage because, during nesting, bright feathers would make them more visible to predators. In both cases, there seems to be an obvious survival benefit in having bright or drab feathers. The evidence, therefore, could be said to support evolution. This is a standard argument which I've heard made many times before. Such simple attempts to describe the origin of bright plumage sound plausible at first. However, I don't believe they can stand up to scrutiny. I see in them a host of unanswered questions.

First, explanations like this still don't answer why bright feathers evolved. I know what they're trying to say: that the male birds with the brightest feathers are the most successful in attracting mates so the brightest plumage is selected more often over the drab. But evolution is not a directed process. The desire for bright plumage does not cause bright plumage. That would be sort of like saying that dinosaurs evolved into birds because they wanted to fly. For females to select bright feathers in a mate, bright feathers must already be present in the population. If there is not bright plumage, sexual selection will not create them no matter how hot the hens think colorful feathers are!

This tactic of using the survival benefit of a feature as the explanation of why the feature evolved is prevalent in evolutionary philosophy. I wrote about this a while back after reading an evo-article that said crying evolved as a way for humans to garner sympathy from each other. No it didn't. Still, I hear stories like this all the time: lions evolved heavy manes to protect themselves while fighting. Giraffes evolved long necks so that they could reach the leaves at the tops of trees. Poisonous frogs evolved bright colors to warn away predators. The list goes on and on. It's about as ridiculous as believing that Michael Jordan grew tall in order to play basketball. Merely pointing out the survival benefit of a trait is not a sufficient explanation of how or why the trait evolved.

Another funny thing about these types of explanations is that they are so flexible that they can describe anything. Male birds evolved bright feathers to make themselves more attractive to females while females of the same species evolved drab feathers in order to make them less noticeable to predators. Wow! Members of the same species evolved completely opposite traits in exactly the same environments for completely different reasons.

I've also heard that humans evolved altruism because there is a survival benefit in a peaceful, cooperative community. Except, of course, when we express aggressive behaviors like fighting, raping, and killing each other. In that case, years of field research has taught us that we're acting the same way as our cousins, the chimpanzees. One story... er, I mean, “study,” says that we're monogamous because that insures the greatest chance of rearing our progeny to maturity; but another story says we're habitually unfaithful because our evolutionary success hinges upon leaving the greatest number of offspring.

I'm reminded too how often we hear that similar structures in different species are the result of shared ancestry – except when they're the result of convergent evolution. How predictive can any scientific theory be if it can be used to explain anything – even completely opposite results in the evolution of members of the same species?

Yet perhaps the funniest thing about the Scientific American's explanation is the seeming circular nature of it. Think about it: make birds evolved bright feathers because female birds are attracted to bright feathers. It's a tautology. The next question should be obvious: why are female birds attracted to bright feathers? If evolution were true, the preference for bright feathers is also an evolved trait. The evolution of bright feathers isn't necessary unless a preference for bright feathers had already evolved. Yet how could a preference for bright feathers evolve before there were bright feathers? What a pickle! And by the way, what survival benefit is there to the species for the female of a species to be attracted to the males who are the most visible to predators? That part of the equation isn't as neatly explained.

It's sad, really, that scientists waste their time inventing these “just so” stories that have no value as scientific theories and, frankly, don't even explain anything. They then foist these half-baked ideas upon the unsuspecting public and have the nerve to be appalled that lay people just don't understand evolution. Is this the kind of evolution Bill Nye believes kids need to learn in order to be good scientists?

Good morning, class. Today we're going to talk about bird evolution. Please turn off your critical thinking skills and don't ask any questions.”


Steven J. said...

For females to select bright feathers in a mate, bright feathers must already be present in the population

True, mutation is, as far as we know, random: how a mutation would affect one's chances of passing on one's genes is uncorrelated with how likely it is to occur. Females favoring brightly-colored feathers doesn't make a mutation for brighter coloring more likely to occur. But populations tend to be large, and birds produce lots of offspring. Over time, every possible single-point (and many possible other sorts of) mutation will occur, several times. A trait that is not present in the population in one generation may well appear in subsequent generations.

Think of the ubiquitous E. coli experiment on antibiotic resistance. Yes, they're still E. coli (but then, the parrots will still be parrots). But you can start with a monoclonal (genetically invariant, because derived from a single cell) colony and have various mutations (there are multiple known mutations that confer resistance) appear. These variants will spread if and only if they confer some survival advantage (e.g. in the presence of penicillin). The same, mutatis mutandis, is surely true of bright coloration in birds.

Wow! Members of the same species evolved completely opposite traits in exactly the same environments for completely different reasons.

Wow! I've found perhaps the only creationist alive who holds that male and female roles are entirely interchangeable and face identical benefits and trade-offs from a given trait or variant. You presumably believe that God made drab females and colorful males in the same species for some reason; unless that reason is "random whim," it can probably serve as a selection pressure (or rather, as separate selection pressures acting on males and females).

Yet how could a preference for bright feathers evolve before there were bright feathers?

I remember reading once about an experiment with swordtail fish and a close relative whose males did not have spines on their tails (note: if you suggest that they were not relatives the results are even more striking). It was shown (by equipping some fish with artificial, larger-than-normal swords) that female swordtails did indeed prefer larger tails. But then it was shown that even in the swordless species, females preferred males with swordtails -- although that variant was never observed in the wild. So female preferences can exist for a trait that does not yet exist in the population. There seems no reason this could not be true for bird colors as well as for fish tail ornaments.

Female preferences might be a side effect of other evolutionary changes. Basic concepts in genetics are "polygeny" (multiple genes combining to affect a single trait) and "pleiotropy" (a single gene affecting multiple traits). A preference for bright colors might be a mere side effect of some entirely different adaption, and might exist yet be irrelevant if the preferred color mutations never occurred (as with the females of the swordless fish).

On the other hand, I tentatively bring up one of those "just-so stories" that you (like Stephen Jay Gould) mock, not entirely unjustly: there is a hypothesis among evolutionists known as the "handicap" or "honest signal" principle. If you can survive and thrive despite a seeming disadvantage, you must be good and have genes that would be an asset to a female's offspring. On this view, bright colors would be an advantage (to a male) just because they attract predators: "if they can't catch me when I'm advertising my presence like this, just think of the evasive skills I could give our kids!" Of course, neither the female or male is actually thinking this way, but instincts that lead them to behave this way would be favored over other instincts coded for by other genetic variants.

Steven J. said...

Conservapedia's list of "counterexamples to evolution" includes a very weird one, I think (I'm not holding you responsible for anything on Conservapedia, of course; I'm just noting what started this train of thought).

Evolution cannot explain the lack of genetic diversity among the Homo sapiens species. Were evolution and the Old Earth theory true, the human population would show a much larger genetic variance. Some scientists have stated that a troop of 55 chimpanzees contains more genetic diversity than the entire human race; this would support the idea that all chimps are descended from a relatively large initial population while all humans are descended from a much smaller initial population (two people, perhaps).

Either the author of this article forgot that he's supposed to believe in the global flood of Noah between the creation week and today, or he's a troll pretending to be a creationist. That's not your problem, anyway. But it seems to me that this raises a different problem for creationists, including you. If young-earth creationism is true, all humans are descended from three couples (including three brothers) aboard the Ark. That's not a lot of genetic variation in the starting population, but it's probably a lot more than among the single pair of apes from whom chimpanzees are supposed to be descended (and it might be worse than that: if chimps and gorillas are the same "kind," then that single pair had to give rise not only to five subspecies of chimps but two species each of chimpanzee and gorilla and all their genetic variety.

From an evolutionary perspective, this suggests that humans went through a "genetic bottleneck" in which our ancestors were reduced to a few thousand breeding individuals (not just six), while chimps did not go through such a bottleneck, at least not in the last few million years. But from a creationist perspective, chimps must have gone through a genetic bottleneck even more stringent than that through which our ancestors passed (there's no hint in the Bible -- or archaeology -- of a post-flood catastrophe that reduced humans to a handful of breeding individuals; even major catastrophes like the bubonic plague didn't cut our population by more than, say, one-third).

So it strikes me as a prediction of young-earth creationism that humans should have greater genetic variety than chimpanzees (or, indeed, any unclean land vertebrate species). Old Earth creationism, which generally posits a purely local flood, could still hold that chimps are descended from potentially scores of thousands of pairs of chimps in unflooded Africa, while humans are descended from only three pairs aboard the Ark, so this isn't an argument against old-Earth creationism. But I'm wondering how you'd deal with it.

RKBentley said...

A couple of points:

You seem to be saying that bright feathers in a large population is inevitable and, once it appears, nature can select the preference for it. I disagree with the notion that it's inevitable. I saw a pro-evo video the other day that attempted to discuss the rise of new information in the genome. It gave a hypothetical example of a population of black beetles suddenly having green beetles too. If that happened, I would be more apt to believe evolution were possible. However, the only real world example they could give was nylon-digesting bacteria. If I saw a new color appear in dogs (like green, blue, or purple coats), I would concede that truly novel traits can appear in a population – but they don't. We never see new colors appearing even though we've observed literally thousands of generations of dogs.

But even if some new color of feather did appear, what compelling reason exists for nature to select that as the preference among females? There has to be such a survival benefit that the preference overtook the population in most species of birds but it's hard to even think of why males with drab feathers who will likely live longer would be passed over in favor of males who are more likely to be eaten by predators.

Now I know that males and females in any species face different survival challenges. My point is how ridiculous it sounds to merely describe the survival benefit of a trait as though that's the reason it evolved. I could probably find the survival benefit of nearly any characteristic: fast/slow, bright/drab, short/tall, fat/skinny, etc. Let's face it, every species must have some method of surviving so explaining how it survives doesn't explain how it evolved nor why it evolved this way compared to some other way. Cheetahs evolved to become fast runners so they can catch more prey. Turtles evolved thick shells because they move so slowly that they need armor protects them from predators. There's nothing predictive to be had from a theory that could explain any outcome.

Your example about a swordless variety of swordtails is mildly interesting but I hardly see how that solves your cart/horse dilemma. The swordless fish are likely mutated descendants of the sworded variety. Therefor, the preference for long swords is already present in the population even though the swords have been removed.

To answer your question of how I would answer Conservapedia: First, I would have to even examine the claim that there is greater variety among chimps than humans. If I limited a sampling of humans to only 50, I could end up with an extremely varied sample. A larger sample, like 7 billion humans, would make the entire sample more homogenous according to the law of large numbers.

Assuming for a moment that their claim is true, I would say that it was probably in the mind of the author that God only created 2 humans while He created a larger population of chimp-kind which probably includes chimps and bonobos (I don't think it includes gorillas). Could a larger initial population mean the animals on the Ark carried more potential for variety than the humans on the Ark did? I ask only because I'm speculating and haven't studied it yet. Any way, those are some of my thoughts on that subject.

God bless!!

Steven J. said...

The swordless fish are likely mutated descendants of the sworded variety. Therefor, the preference for long swords is already present in the population even though the swords have been removed.

Note that on this scenario, the swordless mutation would first occur in a single individual, in a population in which females preferred males with swords. So when the mutation was expressed, the individual would be less likely to find a mate and pass on its gene for swordlessness. That sounds to me like a recipe for the mutation, not sword-tails, vanishing from the population. Of course, the swordless variant might be sufficiently fitter in other ways (e.g. evading predators or needing less food) to make up for being less attractive to females -- but in that case, I'd expect females who didn't care for sword-tails to also be fitter (i.e. more likely to pass on their genes -- including their genes for not liking swords on tails -- by virtue of being more likely to mate with males whose genes made their offspring likely to survive. So the only way I can see your scenario working is by magic -- e.g. angels going down and deleting all the genes for sword-tails in a single generation. I think "females in a whole group of fish happened to prefer sword-tails, whether or not they ever happened to have existed in that species," is a more reasonable hypothesis.

Could a larger initial population mean the animals on the Ark carried more potential for variety than the humans on the Ark did?

New York City has about eight million people, of a vast variety of races, colors, and ethnicities. Dugger, Indiana, has about a thousand people, nearly all of them white. If I pick one person at random from each city, the one from New York is more likely to be non-white, non-European, etc. But is he at all more likely to have, as a single individual, a greater range of skin colors, blood types, hair textures, etc. than the individual from Dugger? One person is one person. He can have no more than two alleles at any given locus in his genome, no matter how diverse his background. Likewise, the two ur-chimps would have had, at most, four alleles per locus. Noah's sons and daughters-in-law might have had fewer variants, but obviously not much fewer (just given the number of variants at some loci that we have today).

I think you're confusing "variation" (what variants exist) with what variants are common and which are rare. Yes, a sample of seven billion will show that some variants are very rare, and others are more common that a small sample might indicate (e.g. a sample of fifty might by chance show only one instance of an allele that is actually present in a large minority -- or even a slight majority -- of humans). But the total number of variants is not going to get smaller as the sample gets larger (a sample of 50 might omit entirely a variant existing in, say, half a percent of the population or less). What we do know is that samples of humans (taken from many places across the globe) show a smaller total count of alleles at various loci than samples of chimpanzees (taken from one chimpanzee band) do.

RKBentley said...

Steven J,

All this talk about the genetic variation in a troop of chimps is a little off topic of my post but it is interesting so I'll add a few more thoughts.

First, I'll clarify my point about the sample size. In statistics, the larger a sample is, the more likely it is to represent the entire set. On an island of 50 people, the average height may not fairly represent the average height of all humans. Any individual human could vary widely from the mean but if you sample enough of them, you'll have a good idea what mean truly is.

I'll also explain my point about the genetic potential of the animals on the Ark. You and I don't really seem that far apart. I have 8 great grandparents, 4 grandparents, and 2 parents. They are/were all Caucasian. I married a Caucasian woman. Her parents, grandparents, and great grandparents were also Caucasian. What color skin do you think our kids have? Correct, they're Caucasian as well. What other skin color could they have had? However, if one of my parents had been very dark skinned, even if I were lighter skinned, I have the chance of passing the dark skinned trait on to my kids.

We see this same thing in dogs. Two, pedigreed Irish Setters will have red haired pups. I guarantee it. However, if two mutts whose parents were also mutts were to have pups together, I can't guess what color their coats might be.

The people on the Ark were probably middle brown skinned. Their children (obviously) could have skin tones ranging from very dark to very light.

Finally, I'm not sure how exactly to quantify variation. In some features, like average height, it might be easy but how do we quantify the difference between a domestic cow and a buffalo? Certainly we can compare likeness in the genome (ie, 95% similar) but even 4-5% of genetic difference can make a remarkable difference in morphology.

God bless!!