Friday, January 04, 2013

Jumping for Joy

Jerry Coyne has posted a video of a happy young antelope jumping up and down in a style called "pronking" or "stotting" [Antelope pronking].

If you're a certain type of evolutionary biologist you will immediately ask yourself what kind of selective advantage could have led to the fixation of stotting alleles in antelopes? Here's a list of possibilities that Jerry offers ...
  • It allows an animal to jump out of high grass to look for predators
  • The behavior startles the predator, giving the gazelle more time to escape
  • It’s an alarm signal (like bird alarm calls), alerting herd members that a predator is nearby. This would probably evolve only if herd members were closely related, so the behavior could evolve via kin selection (assuming it’s individually maldaptive, which isn’t proven).
  • It’s simply play behavior. But not only the young do it: adults pronk too when they’re chased by predators.
  • It’s a way, in young gazelles, of letting the mother know the baby has been disturbed. This may be one function, but doesn’t explain stotting in adults.
  • It confuses the predator. Presumably a herd of gazelle, all pronking, would puzzle a pursuing cheetah or wild dog, making it hard to pick out a given individual to chase. I don’t believe this for a second; predators aren’t that dumb, and in fact a predator would probably either learn to or evolve to concentrate on the stotting individuals because they might be easier to catch. (This “confusion” explanation was once used to explain zebra stripes: it might be hard to single out one zebra in a mass of fleeing stripey equids. But see my earlier post on another explanation for stripes.)
  • It’s a way to attract mates, possibly by showing how fit you are. Sage grouse in the western U.S. form “leks” in which males group together and jump up and down for hours (making loud noises at the same time) while the females watch from nearby. Invariably it is the males who jump the longest that are chosen as mates. Females want a fit father for several reasons. This doesn’t wash for gazelles since both sexes do it, and not in a sexual context.
  • This is a favored hypothesis: the “honest signal” theory. This posits that the behavior is saying to potential predators, “Don’t bother trying to catch me as I can bounce really high, so imagine how fast I could run if I wanted to!” In other words, the behavior deters the predator from attacking that individual.
  • This is the hypothesis I find most credible: stotting warns the predator that it has been seen, thus discouraging it from pursuing the stotting animal. (Predators like to sneak up on a prey, getting as close as possible before they’re detected.) That is, stotting evolved via individual selection. Remember that predators often don’t go after a whole pack of quadrupeds at once, but single out certain individuals—often young or weak ones—to pursue.
Here's another example of animals jumping up and down in a stylized manner. Surely there are specific alleles that make them behave this way? And the alleles must have become fixed in the Maasi population by natural selection. In other words, it has to be an adaptation, right?

How many just-so stories can you think of?


  1. If I absolutely must invent some adaptationist hypothesis, how about this one:
    It evolved initially because of the various adaptations associated play(practice for life) in the young, but the fact that it persists in and through adulthood is the byproduct.

    So if I had to go with one of those he suggested it would be the 4th one down with the slight modification that adult play is largely a byproduct.

  2. It's an absurd comparison. You can do better.

    1. Agree with Kerry...

      How do you know that the antelopes are 'happy'?

    2. @ Kerry Cunningham,

      Why is it absurd?

      It is actually a very good example of this whole discussion. If you found only 1 subpopulation of an animal engaging in an odd behaviour, there would be millions of adaptive hypotheses to explain it. But one group of humans doing something something as unusual, and we immediately conclude it is not adaptive ("just culture!). So why the difference?

  3. Posts like that are one reason I've concluded that Coyne is at heart an evolutionary psychologist. I know he prudently declines to openly advocate for any of the published work done by avowed evo-psych, criticizing their performance. But Coyne doesn't seem to have any criticisms of the field's basic postulates. Or am I just not familiar enough with his work and blog?

    1. Many web sites have a prominently displayed text box with the word "search" sitting adjacent to it.

      This little box is your friend.

    2. Everything I've read by Coyne on evolutionary psychology is surprisingly like people who agree that any particular theology or church or religion is mistaken, then everywhere else blandly talk of religion being the fount of morality, etc. Like so many Christians, it's always a personal failure, not a failure of the ideology.

      In this case, he takes seriously the idea that this behavior must be genetic and must be adaptive for no reason at all. Being cautious about any particular explanation of this genetically adaptive behavior doesn't address the question.

      And when I've used the search and internal links I've found the same pattern.

      But if Prof. Coyne has profound reservations about the modularity of the mind; the difficulty of operationally defining a propensity; the instability of the environment producing the ESS; the absence of evidence for hereditary behaviors in general; the absences of evidence for differential behaviors in population demes; the legitimacy of positing unobservable intermediates between genes and behavior; the neglect of genetics in evolutionary psychology....well, these topics might be found in quite a few contexts other than "evolutionary psychology." This is especially true if Prof. Coyne wished to avoid direct confrontation.

      The search function isn't magic. Also, it doesn't even attempt to cover Prof. Coyne's professional work. Mentioning the search function isn't a reply, except to strongly hint that one shouldn't question. Please clarify: Was the problem criticizing Coyne in particular? Or asking for the benefit of someone else's greater experience instead of doing all the research myself?

    3. If there was any strong hint in my reply it would be that it is bad manners to wank in public.

    4. I see that you're an authority on bad manners.

      I understand what you're all about now. Thanks for the input.

  4. The mocking comment about the Masai dance is about what I would expect. Much to our good fortune, Darwin and Wallace were at heart population ecologists (another ecologist, E. Blyth, almost got it right) and prepped to understand adaptation. Had the discovery of biological evolution been left to biochemists, paleontologists or (ugh) embryologists, we would, in my humble opinion, still be fumbling about in the dark. After all, it was the geneticists, paleontologists, and embryologists who crafted Bowler’s “Eclipse of Darwinism”.

  5. humans have culture
    antelopes don't

    this behavior isn't universally human; most human societies do not practice this (just as most societies do not practice foot binding). Since evo psych is generally interested in human universal (since that would for them indicate a pervasive, selected-for features), my guess is this would not interest an evolutionary psychologist.

    (but I may be wrong)

  6. Could be a spandrel behaviour.

  7. Stotting, not "strotting" [sic].

  8. humans have culture
    antelopes don't

    And you know this exactly how?

    1. Jeffrey, your question occurred to me too, and I think that the answer depends on whether the word "culture" and any of its definitions are applicable to animal behaviors.

    2. I know antelopes don't have culture because I read a book by an antelope (he wanted to be an actor but ended up an sociologist - imagine that) called 'Antelopes: Why We Don't Have Culture'. Alternatively, one might know this by being aware of what the word "culture" means or, possibly more importantly, what it doesn't mean.

    3. I know that no antelope, just like Luther Flint, has ever crafted a Shakespearean sonnet or built a space station.

      That takes transcendence, or so it has been asserted.

      But I'm sure there's some sort of naturally explained supernatural explanation for all this.

      Now I would define culture as the transmission of information across generations through non genetic means.

      We know that our primate cousins have culture to varying degrees and we have also seen similar behaviour among other species such as crows.

      It's not too much of a stretch to postulate cultural transmission of behaviours in other species as well.

    4. Still obsessed with me I see. At least you managed to to say something about the point I made this time (albeit complete nonsense). And so, in response, if by "culture" you mean a few learned behaviours then yes, perhaps antelopes have culture, but if by "culture" you mean culture then no they don't. So if you want to believe stotting may be a manifestation of the zeitgeist in Antelopeland then go right ahead and believe it. It will fit in nicely the rest of your crackpot views that render you unable to distinguish a dog shitting, or dog shit, from shampoo, or Shakespeare.

    5. I don't claim that any or all antelope behaviour is cultural.

      Only that this a testable hypothesis.

      And what is culture other than a group of learned behaviours ?

      And as for distinguishing dog shite from Shakespeare, we need only compare the cloacal outflow of Luther Flint to the iambic pentameter of the Bard.

      For someone who denies their primate heritage you sure fling poo like one.

    6. Yeah, it's testable, and the test came back negative. To find out why, just look up culture in a dictionary.

      And I don't deny my primate heritage, it was just so long ago and so much has happened since, that it's of almost zero interest to anyone (not you) who can tell the difference between dog shit and Shakespeare, and anyone (again not you) who is more interested in the latter than the former.

  9. This mockery strikes me as unfair - nobody seems to have noticed, or if they noticed they haven't pointed out, that Coyne went on to say: "Now all or some of these explanations might operate simultaneously, or they might all be wrong ... for right now, there’s no highly convincing explanation for stotting."

    I wonder if anyone else can find something wrong with that conclusion, because I know I can't.

    1. The "confusion" stems from Coyne's comment "Yet, contra Larry Moran (who will probably weigh in here now!), I think the behavior is an adaptation."

      The critisim is not that he has picked the wrong adaptive story. The critisim is that he assumes that the answer as to why must be an adaptation.

    2. As this is bad because ... he's not allowed to think that? Despite evidence that it is common to certain types of geographically separate species that live in certain types of habitat?

    3. @JimV

      See the video in this post for a discussion of why asking "what is this adaptation for..." can lead to nothing but a hypothesis tossing exercise.

  10. You used to have links to previous or following posts in your left column. Now all there is is a message "There was an error in this gadget" before and after the publicity for the Principles of Biochemistry.

    Happy New Year!

  11. I think pronking is an efficient mode of locomotion for a deer.

    He may be benefiting from the elasticity of his muscles so is consuming much less energy than you'd expect.

    It's good for navigation since he's higher up.

    Sound is only in bursts so it might be quieter than galloping. The dear can hear better because when he's airborne he can gather better sound information about his surroundings. Like the angle the predator is approaching.

    It may be technically harder for a predator to hit a pronking target than a continually moving target.

    In a social situation the animal can call attention to itself.

    It's probably fun. :)

  12. ...a happy young antelope jumping up and down ...

    How do you know the antelope is 'happy'?

    1. How do you know that he isn't?

    2. Um...Larry was the one making the claim that they were happy. The onus is on Larry to provide the necessary evidence for this claim.

  13. Maybe this is just the way antelopes run when startled? I don't know, just an uneducated guess. It sure does look cool though! I think we can tell animals are happy the same way we can tell other humans are happy...they exude joy and playfulness, and at that moment are relaxed, as in not having to run for their lives. I understand that joy is considered a 'human' emotion...but why do we think that humans have the market on any kind of meaningful emotion?

    1. "I don't know, just an uneducated guess."

      I wouldn't worry about it overmuch. Seems par for the course.

      "I understand that joy is considered a 'human' emotion...but why do we think that humans have the market on any kind of meaningful emotion?"

      Well, exactly.

  14. If a behaviour is exhibited instinctively and in play, even in individuals raised in isolation, and it occurs in response to a predator - a particularly punitive weeder of maladaptive alleles - then I don't think it at all unreasonable to assume an adaptive basis.

    Of course one has to establish a genetic basis before adaptation can be demonstrated. And, further, one has to demonstrate that there is a causal relationship between the gene and survival. Even having done that, the reasons for the link may remain forever obscure. Without interviewing the predator, one cannot readily determine what it is about stotting individuals that (if true) makes them less frequent targets.

    But a default assumption that phenotypically visible characters result from adaptation is perfectly valid, even though it is bound to be wrong some of the time.

    1. Like male-dominace aggressive behaviour in primtes! Clearly the result of sexual seletion for the most fit alpha-males, tuned to perfection in their natural enviroment.

      Oh wait...

      ...could just be culture after all.

      My problem with the in-laid assuption of anything is that it eventually become FACT(TM), even if there is no evidence to support it.

      To call on anther example often discussed here, how many people continue to argue that "each extra bp in the genome costs so much ATP - therefore big genomes must have an adaptive significance to justify the massive energy expenditure". This myth that replication is a significant contributor to the energy budget of a multicellular organism is everywhere.

    2. Other Jim

      I'm genuinely curious. What is the evidence for the claim that replication is not a significant contribution to the energy budget of the cell? Can you go through the calculation please?

    3. Other Jim - I'm absolutely with you on the DNA cost argument. But that is a different kettle of fish. The 'visible phenotype' of an extra bit of DNA is an extra bit of DNA. If the organism is a junky eukaryote that eats junky eukaryotes, it's unlikely to be significantly limited, and generate an s value to take it over the Nes threshold by saving on a few building blocks when compared to marginally less lean individuals from the same population. (It might be enhance survival, though not reproduction, if it could instantly become the leanest possible individual, but of course it can't. And organisms retain genome duplications and supernumerary chromosomes with little apparent effect.)

      So yeah, that popular assumption can be challenged, initially from the armchair. But as regards the possibility that variant behavioural alleles
      a) exist
      b) have an adaptive basis


      Why the hackles when anyone mentions potential adaptive significance to behaviour? There must be some, somewhere, FFS! Animals don't learn their every last manoeuvre. Are people afraid of some Ev-Psych foot-in-the-door, or the Dread Hand of Sociobiology?

    4. @ Anonymous

      Start here, and go into the references.

      @ Allen Miller

      "Why the hackles when anyone mentions potential adaptive significance to behaviour?"

      No hackles. Just my honest critisim that, especially in behavioural discussions, there is an explicit assumption that behaviour X is adaptive for Y reason, with little real evidence to back it up. This is because it is hard work, and finding out how these things work will require a huge effort and a very clever set of experiments in many cases (how will we get the "experimental" leopards to not take their prey up the tree to test the hypothesis that the behaviour is to keep their kill away from other preditors?).

      Those reviews I linked to are give good examples of how behaviours in animals can shift rapidly - even in a case where a direct link to sexual access and fitness could be (and was) drawn. This leads me to be very skeptical of most claims that a simple bahaviour-to-fitness-difference line can be drawn for any one given bahaviour. I'm sure they exist. But evidence is lacking, and with the plasticity of behaviours and the spandrels-of-another-behaviour potential, I would be much more careful.

      My concern is that the just-so stories are catchy little memes. They stick in people's heads and become "truth", even if they are nothing more than story-telling exercises. This is not how science should be done.

    5. T. O. Jim - I certainly wasn't espousing any particular 'story'. Nor was Coyne, other than noting which he favours, necessarily tentatively. But on the distinction (which seems to be rather a temperamental one) as to whether adaptation, spandrel, neutral variation or culture is the 'likeliest' answer, I simply tend to go for 'adaptation'. Perhaps less so in the higher primates, which do appear to be a special case. And I'll still be wrong a lot of the time. Of course one should be open to all the possibilities. But there is as much a tendency to go for 'just-ain't-so' stories! Gouldian Adaptation-reactionaries, or something.

      I'd simply look on them as hypotheses. As I noted in my first post, work is indeed required to determine if a trait is truly an adaptation - and ditto for whether it is 'truly' a spandrel, neutral etc. Work that is difficult at the best of times, even without the ethical minefield and generation times that make humans an unfavourable experimental subject!

    6. Within a group of scientists, I completely agree. We all know that were are adding caveats to what we say, and that we agree to adapt our views as the data piles up.

      My concern is in the communication the the wider public, or to students, where they do not necessarily play the same game we do. I think blogs (or the Coyneian Not-A-Blog) are clearly in the public domain.

      We need to be more careful, and more precise.

  15. Historically the fixation on genes, exposed in the stotting Just So stories, is part of the scientific racist movement. As an apparent follower of that movement, Prof. Coyne has indulged himself in posting a tirade by one Condell. Condell retails a nauseating number of lies, such as the claim that Israelis don't target civilians!

    Also, Coyne and Condell have apparently decided that the Quran mandates that Muslims slaughter all Jews and naturally and inevitably pursuing their religious goal. Why this religious mandate is only being acted upon after a thousand years? They don't say. Nor do they comment on Christians and Zionists wanting Palestine because God gave it to the Jews, although that would seem to be a religous motive too. Criticisms are dismissed as legalisms.

    And of course, the fact that Israel is a nuclear power with reported plans to carry out a genocidal assault on Arab peoples is unworthy of comment. Why mushroom clouds are better than crematoria is a mystery to me. Of course, ranting about the Islamic menace to Jews when Christians are the ones who carried out a genocidal assault on Jews takes truly extraordinary gall. I suspect it takes powerful bigotry to blind yourself so thoroughly.

    Is being an atheist really enough reason to let Prof. Coyne off the hook for his outrageous beliefs?

    1. Well that's a little more interesting than the Darwin was a racist and responsible for the eugenics movement therefore Hitler trope.

      I hadn't realized the Condell and Coyne were collaborating, when can we expect the video ?

      You haven't actually read the article at Jerry Coyne's website, have you ?

      And I'll go out on a limb here and predict that you are some sort of troll who has been banned at Jerry Coyne's website. Perchance do you post under multiple aliases ?

      You did get one thing right, what you say is "unworthy of comment".