In biology evolution means merely change and most textbooks describe biological evolution as a change in the frequency of alleles from generation to generation. However, on debate boards like these, "evolution" usually means some form of neo-Darwinism, to wit, the claim that simple life originated somehow in the past, that all living creatures share a common ancestor, and that this process has been shaped by descent, modification, and natural selection over billions of years.
Natural selection is normally held up as an obvious truth. "Imagine," the proponents say, "an animal that is born without eyes while all others of its kind can see. Surely you can see that the chances of this animal surviving long enough to pass its genes on are greatly reduced." After sage nods all around, natural selection is enshrined as the guiding pillar of evolution.
Nevertheless natural selection has its share of challenging themes. The peacock's tail, for example, is a puzzling situation. Surely this tail does not enable the peacock to trap food better or to evade predators more easily. What good is it? How could such a bizarre trait have evolved over countless generations of feral cats, raccoons, and the occassional tiger making its owner into lunch? The answer, we are told, is sexual selection. A standard pro-evolution explanation can be found at http://www.dbskeptic.com/...and-how-the-peacock-got-its-tail which theorizes that an ornate train proves that the peacock is healthy, virile, and a good genetic contributor for the females in question.
However, a seven-year study of peacock mating behavior can be summed up by its title: Peahens do not prefer peacocks with more elaborate trains (http://www.researchgate.net/...ks_with_more_elaborate_trains ). The authors of the study attempted to pin down exactly what it was about the trains that peahens went for. Was it length, symmetry, number of eye spots, or what? The answer is simple: None of the above. The theory of peacock sexual selection has been falsified.
This result has surprised many especially in light of a previous study by Marion Petrie in which she (supposedly) discovered that peahens do indeed prefer males with more eyespots. The appropriate way to express the new findings is simple: Marion Petrie's results could not be replicated.
Ioannidis pulls no punches in his paper which boldly states, "It can be [proved] that most claimed research findings are false." What exactly is the problem? The first problem is simple: Science is based on a logical fallacy that has been papered over by Bayesian statistics. Going to the heart of the matter he states, "...[this] is a consequence of the convenient, yet ill-founded strategy of claiming conclusive research findings solely on the basis of a single study assessed by formal statistical significance, typically for a p-value less than 0.05."
The second problem is bias. Whether we are talking about researchers looking for and finding what they want to find and ignoring findings that don't confirm their beliefs (confirmation bias), researchers dropping subjects from the study in order to obtain that tantalizingly close 95 percent statistical confidence interval (selection bias), or when a publisher chooses to publish a study that shows a relationship and not to publish a study that shows no relationship (publication bias) the results are the same. Ioannidis writes, "Claimed research findings may often be simply accurate measures of the prevailing bias."
How much bias is there in evolutionary biology research? Only time will tell.
"...nobody to date has yet found a demarcation criterion according to which Darwin can be described as scientific..." - Imre Lakatos
I'm glad that you've brought this to our attention: it's an interesting study with very relevant results for the evolution-vs-creation debate.
However, I'm a little dismayed by the way you've drawn conclusions. I haven't read the Ioannidis article you talked about, but, based on your paraphrasing of the article's conclusions, I think you have fallen victim to the same biases you discussed, and of which you accuse evolutionists.
For example, you seem to have exercised confirmation bias by sharing with us the paper that rejects the sexual-selection hypothesis of peacock feather trains, but have neglected to mention the following papers, which have upheld modified versions of the sexual-selection hypothesis:
Hale ML, Verduijn MH, Moller AP, Wolff K & Petrie M (2009) Is the peacock's train an honest signal of genetic quality at the major histocompatibility complex? Journal of Evolutionary Biology 22(6): 1284-1294.
Dakin R & Montgomerie R (2011) Peahens prefer peacocks displaying more eyespots, but rarely. Animal Behaviour 82(1): 21-28.
Dakin, R (2011) The crest of the peafowl: a sexually dimorphic plumage ornament signals condition in both males and females. Journal of Avian Biology 42(5): 405-414.
Hebets E, Stafstrom JA, Rodriguez RL, Wilgers DJ (2011) Enigmatic ornamentation eases male reliance on courtship performance for mating success. Animal Behaviour 81(5): 963-972.
The first paper shows that feather-train length of male peacocks is, in fact, correlated with some measures of male fitness. However, they found no evidence that feather-train length directly influences female mate preferences. So, perhaps feather train is a side effect of the real selective signals?
The second paper shows that ornamentation does indeed have a positive impact on reproductive fitness, but with considerably less precision than was previously thought. So, fine-scale variation in ornamentation does not influence female decision, but large-scale variation does.
The third paper shows that other characteristics of the peacock can potentially modify the peahen's decision-making process: specifically, the crest on the male peacock's head is correlated better with some metrics of health and fitness than is the feather train, and may provide a finer-scale stimulus in female mate preference.
The final paper deals with wolf spiders, but shows that in some settings, complex ornamentation has less benefit than in others. These peafowl studies are generally conducted on feral peafowl outside their native range, so it isn't unreasonable to suggest that the physical environment has influenced the peafowls' behavior.
In combination, these papers indicate that the feather train does play a role in sexual selection, but that role is not as simple as scientists used to think, and we do not really know what that role is yet.
The story is not complete. But then, in science, the story never is complete: we're always working to improve our knowledge, and we don't stop trying to improve our knowledge when one study raises difficult or uncomfortable questions.
This is a fantastic find, Arriba, and one that will certainly lead to important improvements on our understanding of how nature works.
I would like to pose one question to you: how do you explain how peacocks survive with a handicap like that feather train? The evolutionary explanation is that it provides some benefit that outweighs the disadvantage. We do not know what that benefit is, but, based on the Theory of Evolution, I predict that such a benefit does exist and will eventually be found. What alternative prediction do you propose, so we can test our competing hypotheses?
I once posted some similar articles that mentioned this unreliability of published science articles. Before I found these studies it had already occurred to me that this is almost certainly true-and yet completely circumspect studies continue to be part of mainstream beliefs (like that atomic clocks have been tested and proven to record different times, flying east to west as opposed to west to east).
In the age of Wikipedia this phenomenon has only become even more widespread, false believes have proliferated.
One interesting thought, similar to the peacocks, that I have often thought about is, imagine if man never invented scissors or a razor. Men would be running around the woods with beards dragging four feet from their face, and their hair would be down to the ground, getting tangled up where ever they walked. And our fingernails and toenails would all get so long, they would break off and get all infected.
But Bluejay, don't you think that the whole notion of a cosmetic trait being an indication of an animals fitness, when the cosmetic trait itself is simply a measure of the cosmetic devices fitness, is in itself a pretty funny argument for evolution.
In other words, if you posses a trait which makes you appear more fit, regardless of whether or not it ACTUALLY made you more fit, or if it even made you less fit, but it can fool people, you will pass on that fake fitness indicator. The important feature becomes the fakery, not the real individuals health. I could think of hundreds of examples of this.
Uhhh.....Bolder? When do you think the razor, or scissors, were introduced to Australia? Or to the Americas?
"The Christian church, in its attitude toward science, shows the mind of a more or less enlightened man of the Thirteenth Century. It no longer believes that the earth is flat, but it is still convinced that prayer can cure after medicine fails." H L Mencken
In other words, if you posses a trait which makes you appear more fit, regardless of whether or not it ACTUALLY made you more fit, or if it even made you less fit, but it can fool people, you will pass on that fake fitness indicator.
This trait would be outcompeted by another trait that produced the same display but did not lower fitness in other areas.