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I wonder what are examples of organs/structures/behaviours/cooperation that evolutionary biologists themselves find most difficult to explain -- to explain how they could appear evolutionarily -- within known mutation rates, generation frequency, and known time frames. Excluding issue of appearance of life itself.

Knowing rates of mutation and generation cycle (and population size), it would be possible to estimate time needed for appearance of new feature.

Thus it would be possible to spot counter-examples, such examples that are probabilistically beyond possibility to appear in given evolutionary time. Are such examples known ?

I might be naive, but I think some rare behavioral trait can be a candidate, behavior that does not trigger even once in a lifetime of organism, on average, that triggers really rarely.

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Some people keep presenting the bombardier beetle... –  user132 Dec 23 '11 at 3:05
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@J.M.: sure, but their point is absolutely unexistent... –  nico Dec 23 '11 at 18:20
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This is a classic survey question that begs for arguments not based in fact, but on a gut "feeling" about the likelihood of the evolution of characteristics –  Tyler Dec 24 '11 at 17:51
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@Tyler try suggesting a way to improve this question. It is always valid to question even if it is the paradigm. –  Poshpaws Dec 26 '11 at 12:05
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@Tyler: According to Dawkins, speed of evolution of not gut feeling but is subject to numeric estimates and computer simulation. Rates of gene mutations are known, cycle of reproduction can be estimated, sizes of population can be estimated, hence pace of evolution can be estimated, even if with large estimation error, but still, simulated. –  Andrei Dec 30 '11 at 19:03
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3 Answers

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I won't claim that these are the most difficult things to explain evolutionarily, but these two are hard:

  1. Host-Pathogen dynamics. They start out easy enough, but the interaction between a pathogen and its host is intensely complex. You have the immune system, pathogen-pathogen interaction, the balance between weakening a host and killing a host, dozens of different transmission mechanisms, at least two levels of evolutionary pressure (inter-host and population), etc.
  2. Social/Societal level traits. Evolutionary psychology has, for example, been criticized for not being able to get much past the level of "Just So Stories" in terms of its ability to explain human societal traits using evolutionary theory.
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I agree with (2) simply because it’s very hard to find good evidence (as you mentioned with the “just so” stories). I disagree with (1) since this can be explained by quite easy models and is a classical example of evolutionary arms race. –  Konrad Rudolph Dec 31 '11 at 14:08
    
@KonradRudolph I work on some of those models, and they're less than "quite easy", especially when multiple pathogens are pulled into the equation, or you start working on multiple scales. –  Fomite Dec 31 '11 at 17:20
    
Fair enough, point taken. –  Konrad Rudolph Dec 31 '11 at 17:33
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To answer your question directly, there are a number of examples which creationists like to bring up, such as woodpecker's tongue which is wrapped around its brain or the archer fish which shoots down insects with water and has to adjust it's aim for refractive difference between water and air. These features supposedly 'couldn't have evolved' but of course one's disbelief doesn't make anything true or untrue. This is what Dawkins calls 'argument from personal incredulity'.

Let me also point out a few evolutionary counter arguments to such reasoning.

The presence of selection radically changes what is 'likely' or 'possible' to happen. For example, you wouldn't argue that it's highly improbable that the stones on the beach are ordered by size, if you know that the action of waves orders them in a certain way. Dawkins' weasel (http://en.wikipedia.org/wiki/Weasel_program) also demonstrates this principle.

Another Dawkins' argument is that, contrary to what creationists claim, complex features such as eye don't have to be completely functional to be useful. In the early history of life, when no organism had eyes, any simple system which could distinguish light from darkness could provide a huge advantage to its owner. The simple system can then evolve to a more complex one to provide a competitive edge etc.

Finally, evolution happens over time scales we cannot grasp. We don't have a good feeling of what billions of years of small changes which are selected for can add up to.

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I am avolutionist myself and I have read Dawking. You misunderstood my question. I did not ask what looks unbeleivable in eyes of creationists. That would be easy question.I am asking which examples looks difficult to evoluion biologists themselves. Dawkins gives impressive explanations about evolution of the eye etc. Again, are all feature that easy to explain to evolutioninsts ? Evolutionists not only beleive in evolution. They seek specific explanations. Are not sometimes explanations difficult to find ? What are examples ? –  Andrei Dec 30 '11 at 18:55
    
@andrei what role does belief play in science? –  David May 8 '12 at 7:13
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The Nautilus eye used to be (still is?) a "problem" and became a poster boy for creationist arguments. It has a pin-hole camera eye, which is the highest resolution non-lens eye. However, I understand that several genera arose during the Cambrian and the existing species haven't changed much since. So, the Nautilus saw fit to develop a sophisticated but non-optimal eye several hundred million years ago (other cephalopods have much better vision), but not develop it further.

This may hard to explain in evolutionary terms, although I note that they probably hunt via olfaction not vision.

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At which depth they live. Is there light at this depth at all. –  Andrei Dec 30 '11 at 19:04
    
I found myself skipping the Grasso "olfaction not vision" paper when seeing "marine vertebrates at every scale from small crustaceans to sperm whales" in the abstract. –  mgkrebbs Dec 31 '11 at 0:44
    
@mgkrebbs Yes, I admit not the best start to a paper. –  Poshpaws Dec 31 '11 at 11:36
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saw fit to develop? Please explain this in an evolutionary framework –  David May 8 '12 at 7:11
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