Thursday, August 30, 2007

Dennett on Adaptationism

 
I've been trying to avoid the discussion of Dawkins vs Gould until the results of the poll are in (see left-hand margin). Those of you who voted for Dawkins will need some major reorientation to bring you into the 21st century. My task is enormous. (I know who you are!)

But since I brought up Daniel Dennett in reference to the aquatic ape just-so story [Aquatic Ape Speculation], I couldn't resist quoting him from Darwin's Dangerous Idea. After outlining the main points in favor of the speculation Dennett says,
The details—and there are many, many more—are so ingenious, and the whole aquatic-ape theory is so shockingly antiestablishment, that I for one would love to see it vindicated. That does not make it true, of course.

The fact that its principal exponent these days is not only a woman, Elaine Morgan, but an amateur, a science writer without proper official credentials in spite of her substantial researches, makes the prospect of vindication all the more enticing. The establishment has responded quite ferociously to her challenges, mostly treating them as beneath notice, but occasionally subjecting them to withering rebuttal. ... I have often asked them just to tell me, please, exactly why Elaine Morgan must be wrong about the aquatic-ape theory. I haven't yet had a reply worth mentioning, aside from those who admit, with a twinkle in their eyes, that they have often wondered the same thing.
We all love an underdog but this is going too far. The fact that Dennett can't see what's wrong with the aquatic ape speculation suggests that his understanding of evolution and how it works is vastly overrated. He then goes on to prove it.
My point in bringing up the aquatic-ape theory is not to defend it against the establishment view, but to use it as an illustration of a deeper worry. Many biologists would like to say, "A pox on both your houses!" Morgan deftly exposes the hand-waving and wishful thinking that have gone into the establishment tale about how—and whyHomeo sapiens developed bipedalism, sweating, and hairlessness on the savanna, not the seashore. Their stories may not be literally as fishy as hers, but some of them are every bit as speculative, and (I venture to say) no better confirmed. What they have going for them, so far as I can see, is that they occupied the high ground in the textbooks before Hardy and Morgan tried to dislodge them. Both sides are indulging in adaptationist Just So Stories and since some story or other must be true, we must not conclude that we have found the story just because we have come up with a story that seems to fit the facts. To the extent that adaptationists have been less than energetic in seeking further confirmation (or the dreaded disconfirmation) of their stories, this is certainly an excess that deserves criticism. [my emphasis in red—LAM]
This is classic adaptationist thinking. It assumes, without evidence, that there must be an adaptationist explanation for every feature. Hairlessness, for example, must be explained by some sort of just-so story involving running on the savanna or wading by the seashore. All the stories seem silly—including the aquatic ape speculation—but since one of the stories must be true we shouldn't reject it just because it makes no sense. There's no room for a non-adaptationist explanation in such a worldview.

Let's see how a pluralist might approach this problem.
For many reasons, ranging from the probable neutrality of much genetic variation to the nonadaptive nature of many evolutionary trends, this strict construction [adaptationism] is breaking down, and themes of unity are receiving renewed attention. ... One old and promising theme emphasizes the correlated effects of changes n the timing of events in embryonic development. A small change in timing, perhaps the result of a minor genetic modification, may have profound effects on a suite of adult characters if the change occurs early in embryology and its effects accumulate thereafter.

The theory of human neoteny, often discussed in my essays (see my disquisition on Mickey Mouse in The Panda's Thumb), is an expression of this theme. It holds that a slowdown in maturation and rates of development has led to the expression in adult humans of many features generally found in embryos or juvenile stages of other primates. Not all these features need be viewed as direct adaptations built by natural selection. Many, like the "embryonic" distribution of body hair on heads, armpits, and pubic regions, or the preservation of an embryonic membrane, the hymen, through puberty, may be nonadaptive consequences of a basic neoteny that is adaptive for other reasons—the value of slow maturation in a learning animal, for example.


                        Stephen Jay Gould in How the Zebra Gets Its Stripes
If you are a Dawkins/Dennett adaptationist then your explanations are confined to the sorts of adaptationist just-so stories promoted by the likes of Elaine Morgan. If you are a pluralist like Gould, you have more choices. Some of the pluralist nonadaptationist explanations might be right. In this case I think Gould is more likely to be right about the evolution of hairlessness. Unfortunately, Dennet and his ilk can't imagine such explanations because it doesn't fit with their idea of how evolution works.

76 comments:

  1. Hmmmm... interesting business, very interesting in fact. Looking forward to the Dawkins vs Gould heavyweight title fight. Save me a ring side seat.

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  2. Those of you who voted for Dawkins will need some major reorientation to bring you into the 21st century.

    I couldn't have put it better myself.

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  3. It sounds like you think this is 100% settled. Besides, why is it either/or? I'm sure Dawkins/Dennett would also adapt their adaptationist thinking if they were to be proved wrong.

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  4. As it happens, I just read Dawkins's treatment of human bipedality and hairlessness last night (in The Ancestor's Tale). As it happens, he (more or less convincingly) explores sexual selection hypotheses (one bit of evidence: males are hairier than females), but leaves the matter unresolved.

    Personally, I find the Gould quote kind of stupid in this case. What is "embryonic" about pubic and armpit hair? Head-hair is the first to develop, but it's also by far the furriest part of adults. I don't see this as neotenic at all. How hairy are chimp infants?

    And what is less "just-so" about Gould's idea than an adaptationist scenario? Both are equally speculative. It's one thing to be a pluralist, but I am beginning to think you, Dr. Moran, are a knee-jerk anti-adaptationist. Do you really believe that chimp-level furriness vs. human-level nonfurriness is a selectively neutral phenotypic difference? I'm with Dawkins (if not Dennett) on this one.

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  5. Chimpanzee fetuses have hair on the head, armpits and genitals only. You can try to explain this as a cryptic adaptation, but I'm not precisely holding my breath to hear that explanation.
    In humans, this reflects neoteny (delayed development of a somatic trait) and need not be an adaptation.

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  6. On the bhalf of the daataionists, I muts say that I agree that the "just so stories" term seems to me not specific enough against adaptationism. It's like generally pejorative, I agree.
    I find the other term of Gould, "panglosssian" adaptationism, as much more to the point.

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  7. Sven DiMilo: "And what is less "just-so" about Gould's idea than an adaptationist scenario? Both are equally speculative."

    I'm with Sven here, and will add that both are also, in principle, testable hypotheses. I'm struck by how some people (including the author of this blog) seem to use term "just so story" dismissively, particularly when juxtaposed with an anti-adaptationist spandrel explanation.

    I don’t think anyone is a strict adaptationist nowadays, but IMO, the strict adaptationist approach of assuming a survival value and then proposing a testable adaptationist explanation is a better starting point for understanding some feature or characteristic than a general “spandrel” one, even though all would admit that it could be a spandrel. After all, most of the features of San Marco's Cathedral *are* (metaphorically) “adaptations”, not (metaphorically) “spandrels”. Anyone studying that structure to understand how it functions it would progress faster by assuming every feature had (metaphorically) “survival value”.

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  8. Sorry for not signing: the above anonymous post is mine.

    Divalent

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  9. "some story or other must be true" - this is just a truism; the notion of singling out this quote and criticising it as false is somewhat
    ludicrous. Where does Dennett say the true story has to be an adaptationist one?

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  10. I’m really looking forward to the big fight Larry! (Dawkins vs Gould – my money’s on Gould). Cor! Looks as though things are hotting up for a real mother of a battle! Pah! Who’s interested in science? I want to see some blood. After all, I’m a theist and so I’m used to lots of blood: the inquisition, the crusades, the 30 years war, battle of Boyne, northern Ireland, Iraq…….

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  11. Divalent says,

    I'm with Sven here, and will add that both are also, in principle, testable hypotheses. I'm struck by how some people (including the author of this blog) seem to use term "just so story" dismissively, particularly when juxtaposed with an anti-adaptationist spandrel explanation.

    There's nothing wrong with proposing hypotheses to explain certain features. But not all hypotheses qualify as "just-so" stories.

    A typical "just-so" story, like their namesake in Rudyard Kipling's writings, involves a highly speculative series of historical events that "explain" a particular feature. The adaptive explanations of hairlessness fall into this category. We are asked to imagine how human populations might have behaved in the ancient past in order to justify the adaptive evolution of the hairless condition.

    For the most part, those speculative stories are not testable and quite often the adaptationists are content to leave them untested because the "just-so" story itself is sufficient to convince them that the feature is an adaptation.

    The idea that hairlessness might be an epiphenomenon of neoteny is not a just-so story. It certainly can be tested by trying to establish whether the regulation of human developmental genes indicates a delay in adult features relative to what we see in chimpanzees. If neoteny if correct then it follows that the hair pattern on humans fits with the hypothesis.

    There's a lot of evidence to support the hypothesis. Certainly much more evidence than the evidence to support the idea that humans lost their hair by wading in the ocean or that human males lost their hair from hunting on the savanna.

    I'm curious about something. The neoteny explanation has been around for several decades. Why do you think that adaptationists have ignored it? Why does Dennett insist that some sort of adaptationist just-so story must be true in spite of the fact that he should be aware of the pluralist explanation?

    I don’t think anyone is a strict adaptationist nowadays, but IMO, the strict adaptationist approach of assuming a survival value and then proposing a testable adaptationist explanation is a better starting point for understanding some feature or characteristic than a general “spandrel” one, even though all would admit that it could be a spandrel.

    This is hotly debated. The consensus is against you. The idea of assuming a specific mechanism (natural selection) before you even begin to formulate a hypothesis is considered bad form. Instead, you should ask yourself whether you even need to make that assumption or whether there are other possible explanations.

    This does not mean that you have to assume that a feature is an accident or an epiphenomenon. What it means it that good scientists have to consider that these explanations are possible instead of just leaping to the conclusion that a feature must be due to natural selection because that fits in with their bias.

    The problem with the adaptationists is similar to the problem of the man with a hammer. If all you've got is a hammer then everything starts to look like a nail.

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  12. Konrad asks,

    "some story or other must be true" - this is just a truism; the notion of singling out this quote and criticising it as false is somewhat
    ludicrous. Where does Dennett say the true story has to be an adaptationist one?


    Point taken. It may not be obvious from the paragraph that I've quoted. You need to see it in context where it becomes painfully obvious that the only explanations Dennett is considering are adapationist stories.

    The very next paragraph (p. 245) makes it clear that this is what he's taking about. Dennett says,

    But before leaving it at that, I want to point out that there are many adaptationist stories that everybody is happy to accept even though they have never been "properly tested," just because they are too obviously true to be worth further testing. Does anybody seriously doubt that eyelids evolved to protect the eye."

    Does that make is clear for you?

    Incidentally, I agree with Dennett that eyelids are an adaptation to protect the eye in land vertebrates. But that's not an adaptationist story at all, and certainly not a just-so story. It's just a logical conclusion about the possible origins of a feature based on it's function.

    The problem with adaptationists is that they treat every feature as an adaptation. If the current adaptive advantage isn't obvious then they invent one in the past.

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  13. Larry, when you do write the big post on this topic, I hope you'll list on the bottom links to all your previous posts and articles on this topic, so everything is in one place for ease of use.

    Dennett is even more adaptationist when not writing and carefully editing his writings. Catch him in person and start a discussion and you'll see. He is MUCH more naive about evolution, MUCH more adaptationist than Dawkins, and astonishingly deterministic for this day and age - I bet if he rerean the tape of life a million times, he would expect to see himself writing his books every single time.

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  14. He's not much better on consciousness. Of the books of his I've read, I did rather enjoy Freedom Evolves, though.
    (Of course, the topic of free will has elicited so much bilge from philosophers over the centuries that the bar was set pretty low on that one.) And his recent book on religion was decent, though more as a review of other people's ideas than for any original contribution.

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  15. This comment has been removed by the author.

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  16. Hmm. I need to stack up on more popcorn.

    For an outsider like me this looks like a political fight about null hypothesis and research strategy.

    My pitiful 2 c:

    AFAIU "nonadaptive" mechanisms explain much of the content and functions of the genome. But that doesn't necessarily translate to the phenotype.

    Is there a measurable reason to prefer one specific null hypothesis? If not I guess it is up to the individual researcher to choose a strategy to formulate a hypothesis. Any collective effects may be irritating for the "outgroup" but should eventually reflect the success of the strategy.

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  17. if you can lick your eyes, you may lose your eyelids no problem. Ask geckos

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  18. I doubt that geckos got any advantage from losing their eyelids. Evolution is about what is possible, not about what is..."better".

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  19. The problem with the adaptationists is similar to the problem of the man with a hammer. If all you've got is a hammer then everything starts to look like a nail.

    Does that mean that the problem with the anti-adaptationists is similar to the problem of the woman without a hammer - nothing looks like a nail?

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  20. "Chimpanzee fetuses have hair on the head, armpits and genitals only."
    Now that's really interesting. I'm happy to amend my judgment of the neoteny hypothesis in light of this new (to me) datum.
    But! a) Neoteny is not a satisfying explanation for the maintenance and persistence of (relative) hairlessness, it is more of an explanation for its origin, or the developmental process that causes it (proximately). An ultimate/evolutionary explanation has to account for the fact that hairlessness has persisted in the face of obvious variation in hairiness. Again I ask: do you really think that the density of fur could be a selectively neutral phenotypic character?
    b) "Neoteny" and "adaptation" are far from mutually exclusive--the neotenic trend itself could be viewed as an adaptation. At the very least, variation in relative neoteny must be subject to natural selection.
    c) Given all we know--not speculation, we know--about the power of selection to shape phenotypes, why do you insist on saving adaptation as an explanation of last resort? In a world of obvious nails, why would you first try everything except a hammer? I'll grant that in terms of genetic sequence drift could be seen as more parsimonious than selection, but--sorry--I do not admit the same for phenotypes. Not even for biochemical phenotypes (see Hochachka and Somero).
    d) "Incidentally, I agree with Dennett that eyelids are an adaptation to protect the eye in land vertebrates. But that's not an adaptationist story at all, and certainly not a just-so story. It's just a logical conclusion about the possible origins of a feature based on it's function." I'll try to ignore the superfluous apostrophe (oops! I failed) to simply say that I really don't see this dichotomy you want to draw between "logical conclusions based on function" and "adaptationist just-so stories." Surely, unless data can be brought to bear, this becomes a matter of subjective personal preference.
    e) "if you can lick your eyes, you may lose your eyelids no problem. Ask geckos" Just so! Geckonines (there is a whole sub-family of geckoe, the eublepharines, that do in fact retain eyelids) do without eyelids not because they can lick their eyes, but because the eye is protected instead by a transparent scale, the "spectacle" (as in snakes). Eye-licking functions only to clean the spectacle. As for a potential advantage, they never have to blink!
    f) "Evolution is about what is possible, not about what is..."better".
    Nah. Evolution is about what is "best" from among the possible alternative phenotypes that have actually been tried.

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  21. "As for a potential advantage, they never have to blink!"

    yeah, blinking. What a drag. Much better to cover your eyes with your tongue.

    I love adaptationist speculation when accompanied by an enthusiastic exclamation mark.

    "Nah. Evolution is about what is "best" from among the possible alternative phenotypes that have actually been tried"

    Aaah, nothing like chest-out brazen ideological pride.

    As Dr pangloss said, the nose is made for sporting the glasses; and the legs, the trousers.

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  22. Evolution is about what is "best" from among the possible alternative phenotypes that have actually been tried.

    I think that there is some serious work needed to explore what "best" means in this context.

    I voted for Gould as I think he had a wider view of the mechanics of evolution (although I always thought Dawkins was more easily understood). However to my mind neither fully explored the interactions between genes, development, environment, culture and individual organisms. With such a complex set of interations "good enough for now, all things considered" might be the most appropriate measure of evolutionary effectiveness.

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  23. Ian B Gibson asks,

    Does that mean that the problem with the anti-adaptationists is similar to the problem of the woman without a hammer - nothing looks like a nail?

    No, the pluralist has a full toolkit.

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  24. "The theory of human neoteny, often discussed in my essays"

    Humans are not neotenic apes. In fact, it's more correct to say that we are hypermorphosed apes. Humans are more peramorphic than pedomorphic.

    Is there total consensus about this and does the neoteny hypothesis have no defenders left? No.

    Brian Shea
    http://tinyurl.com/3akwkp

    Michael McKinney
    http://tinyurl.com/3a6d68

    Penin et al.: Human facial morphology is not pedomorphic
    http://tinyurl.com/ypvt7h

    Also see Kenneth McNamara.

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  25. Sven DiMilo asks,

    Again I ask: do you really think that the density of fur could be a selectively neutral phenotypic character?

    I think it's possible. Why do you feel so strongly about ruling out such an explanation?

    I'll grant that in terms of genetic sequence drift could be seen as more parsimonious than selection, but--sorry--I do not admit the same for phenotypes. Not even for biochemical phenotypes.

    Okay. Now I get it. You are a confirmed adaptationist. Everything is a nail.

    Have you ever thought about the phenotypes of tongue rolling and blood types?

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  26. "yeah, blinking. What a drag. Much better to cover your eyes with your tongue."
    Well, I was kind of kidding about that, but since you want to be such a dick about it: for the record, you're not only arguing with me here, but with G.C. Williams (see his Natural Selection, 1992, pp 152-153)...if you think you're smart enough for that, rock on. Williams points out that because of blinking, humans are functionally blind about 5% of the time. You don't think that might be important for a gecko that makes its living hunting fast-moving insects? In contrast, geckos only lick one eye at a time, and can do it at their leisure, having no need to prevent the eyeball from desiccation. Just saying.

    "Why do you feel so strongly about ruling out such an explanation?
    Because I do comparative physiology for a living and I know that pelage thickness has a very large impact on a mammal's energy budget.

    "Have you ever thought about the phenotypes of tongue rolling and blood types?
    Yes. ABO blood groups have been maintained as a polymorphism since the common ancestor of modern humans and chimps so yeah, I strongly suspect an adaptive explanation for that one, even if I don't know what it is (disease resistance?). Tongue-rolling is a tougher case...if I knew more about the anatomical and neurological mechanisms, linkage to nearby loci, etc. I might have a try at that one too, though.

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  27. 5% only? spread out in many small interspersed blinking events? an important "time loss" ? No, I think that's just stupid. Sorry

    I also wonder what's keeping the other eyelidded geckos from saving bigtime on precious blink-time, you know, to catch all those cunning nimble fast little insects.

    The problem is that most adaptationists do not understand what is the actual evidence required to diagnose an adaptation as the result of natural selection, other than point at it with the finger and recitate the obvious current use.

    When formed by natural selection, a new adaptation is an accumulation of several genes with additive effects that would not have occurred without directional selection.

    That is the case that fits the situation where we may say that natural selection "originates" or "shapes" an adaptation. An alternative case is mutationism: an adaptation may arise in a single step, by a single mutation of large effect; thereafter, either selection or drift can make it more or less frequent in the population. Of course selection here is an important restriction and a PART of explaining what morphologies we actually have; but these one-step adaptations cannot be said to have been "shaped" by natural selection.

    In eyelidless geckos I suspect that a single event is responsible for both the loss of the eyelids and the growth of the scale over the eye.

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  28. Organisms hardly ever are as a whole "neotenic"; Traits are. The distribution of hair is an airtight case of neoteny. This paedomorphic distribution pattern defies adaptive explanation.

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  29. Sven DiMilo says,

    ABO blood groups have been maintained as a polymorphism since the common ancestor of modern humans and chimps so yeah, I strongly suspect an adaptive explanation for that one, even if I don't know what it is (disease resistance?).

    Interesting. Here's a chart showing racial and ethnic distribution of blood groups. To me this looks very much like random genetic drift. I'd love to hear how you interpret this data [ABO allele frequencies].

    Have you thought about some other phenotypes like male pattern baldness and whether your second toe is longer than your big toe? What about the shape of your ear lobe? Do you have a good adaptationist just-so story to explain that phenotype?

    How about kinky hair vs. straight hair, full lips vs thin lips, epicanthic fold of the upper eyelid vs no fold, red hair vs blond hair, English ankles vs straight ankles, lots of freckles vs none, long legs vs short ones, big feet vs smaller ones, blue eyes vs brown? Do you have adaptationist explanations for all these polymorphisms? Are they all due to some kind of balancing selection?

    Doesn't it seem a bit silly to maintain that every single phenotype has to be an adaptation?

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  30. Larry Moran: "But not all hypotheses qualify as "just-so" stories. A typical "just-so" story, ... involves a highly speculative series of historical events that "explain" a particular feature. The adaptive explanations of hairlessness fall into this category. We are asked to imagine how human populations might have behaved in the ancient past in order to justify the adaptive evolution of the hairless condition. ... For the most part, those speculative stories are not testable and quite often the adaptationists are content to leave them untested because the "just-so" story itself is sufficient to convince them that the feature is an adaptation."

    With all due respect, I think you’ve erected a strawman version of the adaptationist approach. Your comments might be spot on for the arm-chair naturalist idly speculating about the world for philosophical purposes (e.g., Dennett), but not for a scientist truly focused on understanding some characteristic of some organism. And (again) I fail to see why, by your standard, Gould’s hypothesis is not also a "just-so" story, not withstanding your declaration that it is not. Why is the development of a plausible explanation a "just-so" story if the guiding assumption is that the characteristic is an adaptation, but not a "just-so" story if the guiding assumption is that its an epiphenomenon?

    Larry Moran: "The idea that hairlessness might be an epiphenomenon of neoteny is not a just-so story. It certainly can be tested by trying to establish whether the regulation of human developmental genes indicates a delay in adult features relative to what we see in chimpanzees. If neoteny if correct then it follows that the hair pattern on humans fits with the hypothesis."

    Except for your first sentence, I agree, although I’ll note that the ability to make testable predictions is not limited to hypothesis developed from an epiphenomenonist program. (I’ll also note that this particular test would not falsify the hypothesis if it fails, so it is not a particularly strong test. Indeed, the problem with spandrels is that they can show up in the most unexpected places for the most unexpected reasons; the epiphenomenon explanation can only really be disproved by proof of an alternative (adaptive, sexual, etc) explanation.)

    Larry Moran: "There's a lot of evidence to support the (neoteny) hypothesis. Certainly much more evidence than the evidence to support the idea that humans lost their hair by wading in the ocean or that human males lost their hair from hunting on the savanna."

    I see. So adaptationists are wackos and Lamarckians? :) (see strawman above)

    Larry Moran: "I'm curious about something. The neoteny explanation has been around for several decades. Why do you think that adaptationists have ignored it?"

    I don’t know. Could it be because this "just-so" story has been "around for several decades" and the epiphenomenonists have not really made much progress? :)

    Cheers,

    Divalnet

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  31. "Divalnet "

    opps! to many Friday beers (ummmmm)

    Divalent

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  32. Against Gould:

    Mel Konner in The American Prospect
    http://www.prospect.org/cs/articles?articleId=4520

    John Alcock in Boston Review
    http://bostonreview.net/BR25.2/alcock.html

    I'm a little more charitable than these gentlemen. Gould was right about some things and wrong about others. But come on, it's 2007, not 1977. That goes for Dawkins too.

    Anonymous (not Divalnet; I'm the one who mentioned that a number of authorities reject the neoteny hypothesis of human evolution)

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  33. I meant to write "not Divalent."

    Sorry about the typo.

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  34. sven dimilo: ""Neoteny" and "adaptation" are far from mutually exclusive--the neotenic trend itself could be viewed as an adaptation. ... variation in relative neoteny must be subject to natural selection."

    Correct. In addition as sanders helpfully points out, relative heterochrony is mosaic and dissociable. (And all of us should be familiar with Tinbergen's four questions, which would spare some from erroneous assertions of mutual explanatory exclusivity.)

    sanders: "The distribution of hair is an airtight case of neoteny. This paedomorphic distribution pattern defies adaptive explanation"

    Wrong. See above. But there's more below on why this is incorrect. At best, there is a fairly good case for phylogenetic-developmental constraint - given relative hairlessness - in the pattern of location of (apocrine-associated) body hair tufts in human adults. But this is not a case for hairlessness itself being epiphenomenal. To suggest otherwise is to confuse the intensity of a trait with its spatial arrangement. (In this case, pelage thickness.)

    sanders: "Organisms hardly ever are as a whole "neotenic"; Traits are."

    Quite true. But don't you understand the consequences of this for your argument? The epiphenomenal-neotenic hypothesis is that a host of these traits, including hairlessness are part of a developmentally constrained package of global pedomorphosis, perhaps due to selection for childlike play, exploration, and openness, or some such thing, according to Gould, Ashley Montague and others. (Still adaptationist, just not for hairlessness.) But several authorities have found that the human brain, postcranial skeleton, and face cannot be generally described as pedomorphic. The very dissociability (which you acknowledged) of pedomorphic vs peramorphic vs non-heterochronic evolution in the changes from the African ape LCA of Pan and Homo to modern humans suggests that perhaps they are not, in fact, inherited as a developmentally constrained suite. That seems contrary to the hypothesis that hairlessness was just along for the heterochronic ride. Sure, that's still possible. In any case, this has consequences for which explanation - adaptive or epiphenomenal - requires more special pleading and (what might unkindly be called) storytelling in the absence of empirical evidence.

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  35. anonymous says,

    In any case, this has consequences for which explanation - adaptive or epiphenomenal - requires more special pleading and (what might unkindly be called) storytelling in the absence of empirical evidence.

    The interesting part of your comment is that you spend considerable time discussing neoteny and pedomorphism—perfectly valid scientific concepts. You point out the scientific problems with this hypothesis and refer to evidence against the inheritance of an entire suite of traits. You even bring up valid observations about chimps and humans.

    All these point are fair game in a scientific discussion.

    Now, what about the adaptationist just-so stories? Do you have any scientific comments to make about the speculation that men running on the hot savanna led to loss of hair in humans? How about women wading by the seaside 100,000 years ago? Any scientific comment on that story that you'd like to share with us?

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  36. anonymous says,

    But come on, it's 2007, not 1977.

    Amazing, isn't it? After 30 years the adaptationists still don't get it.

    I don't understand why they have been so reluctant to admit to other mechanisms of evolution. Do you?

    Do you realize (gasp!) that there are still people out there who claim that every single visible phenotype must be an adaptation? Where have they been for the past 30 years?

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  37. Divalent says,

    With all due respect, I think you’ve erected a strawman version of the adaptationist approach.

    This is a common accusation from the adaptationist camp. Personally I don't think it's valid but there's a germ of truth in it so let me address the problem.

    In order to explain the positions one needs to use examples. Naturally, one chooses extreme examples in order to draw the contrast between the pluralist and adaptationist positions. This is usually what triggers the "strawman" accusation because no adaptationist wants to be associated with the extreme position that I mock.

    On the other hand, they do not spontaneously go out of their way to attack those silly just-so stories either. In other words, until we point out the absurdity they seem perfectly content to believe in the most outrageous just-so stories.

    Do you see my point? You can't have it both ways. If you decline to spontaneously speak out against the worst abuses of adaptationism, while at the same time criticizing pluralist explanations, then you are giving tacit approval to the "strawman" version of adaptationism. If the shoe fits ...

    Your comments might be spot on for the arm-chair naturalist idly speculating about the world for philosophical purposes (e.g., Dennett), but not for a scientist truly focused on understanding some characteristic of some organism.

    It doesn't do much good to toss out the "strawman" accusation without explaining yourself. Do you honestly believe that the adaptationist approach is confined to armchair philosophers and not to real scientists? Have you read the The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme?

    There are all kinds of working scientists who abuse the adaptationist program. You can't defend adaptationism by pretending they don't exist.

    Divalent, go back and read your comments. At no point have you criticized the Aquatic Ape Hypothesis or any of the other adaptationist comments, such as all phenotypes are adaptations. You've only criticized the pluralist approach and your main criticism seems to be that it's just as silly as (strawman?) adaptationism. :-)

    If my description of the adaptationist position is a strawman then why haven't you shown us that you reject that position?

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  38. Larry Moran: "How about women wading by the seaside 100,000 years ago?"

    No authority on human evolution (that I know of) takes the Aquatic Ape hypothesis very seriously. There are good reasons why; suffice to say that it's not consistent with the evidence.

    "Do you have any scientific comments to make about the speculation that men running on the hot savanna led to loss of hair in humans?"

    I do.

    If hairlessness is the only derived human trait consistent with endurance running on the savanna, then the status of the 'savanna running hypothesis' is dubious.

    However, if a functional suite of derived traits facilitate and enhance endurance running on the savanna - and there is no other hypothesis that more parsimoniously and consistently accounts for the evolution of that particular combination of traits - then that strongly suggests that there the hypothesis ought to be taken seriously and investigated further. At the very least, it ought not be dismissed out of hand.

    In fact, a functional trait suite is what we see.
    http://discovermagazine.com/2006/may/tramps-like-us/article_view?b_start:int=0&-C=

    Contrast that with the global neoteny hypothesis, which is rejected by a number of authorities. Specifically, it has been rejected as an explanation for the human brain's putatively childlike qualities - which in the Ashley Montagu-Gould model was driving neoteny of these other allegedly nonadaptive traits (e.g. hairlessness) in the first place, as part of a developmentally constrained package. Sanders' legitimate suggestion of trait-dissociable heterochrony, in fact, lends no support to the hypothesis.

    The 'savanna running hypothesis' of hairlessness is far more consistent with the evidence; indeed, far more scientifically supportable, than the 'epiphenomenal global neoteny hypothesis.'

    The lesson here is not that the adaptationist hypothesis is more likely to be correct in each instance, or even that we now know for sure the evolutionary origin of hairlessness. The lesson is that hypotheses ought not to be dismissed without good reason.

    "Do you realize (gasp!) that there are still people out there who claim that every single visible phenotype must be an adaptation?"

    Well, they are as incorrect as those who would dismiss legitimate hypotheses and even whole research programs on a priori philosophical grounds.

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  39. anonymous says,

    ...they are as incorrect as those who would dismiss legitimate hypotheses and even whole research programs on a priori philosophical grounds.

    You still don't get it, do you? The adaptationist program is not being criticized because it postulates adaptation as an evolutionary mechanism. We all recognize that adaptation is a valid mechanism that explains a great deal.

    The adaptationist program is being criticized because it is exclusively adaptationist. No other explanations are offered.

    BTW, I find your defense of the savanna hypothesis very interesting. At what stage in human evolution do you think that men running in the hot sun was so important for so many thousands of years?

    Exactly what kind of selective advantage do you think it was to have a little less hair than your hunting partners?

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  40. As for the specifics of the model, others have discussed it far more ably than I could.

    http://www.physorg.com/news95954919.html

    "Though those adaptations make humans and our immediate ancestors better runners, it is our ability to run in the heat that Lieberman said may have made the real difference in our ability to procure game.

    Humans, he said, have several adaptations that help us dump the enormous amounts of heat generated by running. These adaptations include our hairlessness, our ability to sweat, and the fact that we breathe through our mouths when we run, which not only allows us to take bigger breaths, but also helps dump heat.

    "We can run in conditions that no other animal can run in," Lieberman said."

    Emphasizing developmental constraint is well and good, but developmental modularity provides for considerable developmental deconstraint. If a number of derived and developmentally dissociable traits are functionally integrated with the effect of enhancing a particular activity (say, endurance running in dry heat, or deep sea diving, or arborealism), then that combination demands explanation.

    Has the case been closed on the role of various types of heterochrony and other kinds of developmental change in human evolution, and the adaptive and epiphenomenal manifestations of these processes? Not at all.

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  41. Larry Moran: "On the other hand, they do not spontaneously go out of their way to attack those silly just-so stories either."

    With all due respect, why the hell should "they"?

    Larry Moran: "If you decline to spontaneously speak out against the worst abuses of adaptationism, ..."

    What are you talking about? What "abuses" need to be "attacked"?

    There is an uncomfortable hint in this discussion of something like the political-correctness battle over Sociobiology of the '70. That it's not just the silliness of some "just-so" stories that brings them into your crosshairs, but that there is some (unspoken) moral or political danger that you are concerned about.

    Divalent
    (hope I got my handle right this time!)

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  42. You think our fetal pattern of hair distribution does not relate to having less hair in genral? I said that organisms as a whole are not neotenic, but when several traits are paedomorphic, tey can be related, specially when we are talking about more or less the same trait (hair)

    Say the distribution of our hair has adaptive advantages; for instance, hair on the head indeed seems to fit right in the "run in the sun" hypothesis!

    BUT, can we say that this adaptation was shaped by selection? This is pretty obviously not the case, since that particular pattern preexisted in the fetal life before encountering any such adaptive context. We can indeed discard it having being "shaped" by selection.

    Plus, you really should come clear on whether you think that loss of hair occurred in one step or not, becuase in order to correctly say that hairlessness is the result of selection, you DO require a scenario where succesivly less hairy forms were favored by directional selection: only that way can we say that selection directed hair loss.
    Other than that, and specially in one step changes, selective advantages are secondary to what preexisting development has to offer.

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  43. sanders: "you DO require a scenario where successivly less hairy forms were favored by directional selection: only that way can we say that selection directed hair loss."

    In fact, I suspect that such a scenario is most likely.

    However, a single gene mutation can confer a selective advantage and increase in frequency within a population (for example, an allele that provides lactose tolerance or increased oxygen carrying capacity) without gradual increase in the intensity of trait through directional selection acting on multiple alleles. If hairlessness arose in a single mutation (and not as a selectively neutral pleiotropic effect of a gene responsible for another trait that does enjoy a selective advantage) and increases in frequency - but not intensity - due to natural selection, it is still an adaptation.

    Reeve, HK and PW Sherman, 1993: "An adaptation is a phenotypic variant that results in the highest fitness among a specified set of variants in a given environment."
    (Adaptation and the goals of evolutionary research. Quarterly Review of Biology 68: 1-32. )

    Certainly, hairlessness is not a complex adaptation whether it arose in a single mutation or gradually. (And it is certainly not an "organ of extreme perfection," which some seem to have in mind when they consider adaptations.) However, even if one asserts that a trait that emerges fully blown due to a single gene mutation cannot be an adaptation, this would still be a selectionist model of the evolution of hairlessness, rather than an epiphenomenal one. And it is still part of an adaptive trait complex (described by Lieberman) that inarguably facilitates endurance running. (And it is very doubtful that the entirety of this particular trait complex is due to the constraint of developmental linkage.)

    (If leglessness arose in a lizard from a single gene mutation, and that trait becomes universal throughout a population and ultimately a species due to positive selection, would you argue that leglessness in this species is not an adaptation?)

    The key components of the epiphenomenal neoteny hypothesis of hairlessness are that it is a) selectively neutral, b) necessarily developmentally linked to other traits (at least one of which must be undergoing positive selection).

    Might an epiphenomenal model of the evolution of human hairlessness be correct? Sure. But I doubt it. In any case, let the investigation continue.

    sanders: "selective advantages are secondary to what preexisting development has to offer."

    I wouldn't put it quite that way, but I know what you mean. Selection acts on variants of developmental programs that have been shaped over their phylogenetic histories by a variety of evolutionary forces.

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  44. Divalent says,

    There is an uncomfortable hint in this discussion of something like the political-correctness battle over Sociobiology of the '70. That it's not just the silliness of some "just-so" stories that brings them into your crosshairs, but that there is some (unspoken) moral or political danger that you are concerned about.

    Those of us who object to the excesses of sociobiology and its offspring, evolutionary psychology, do so for many reasons. In my case it has nothing to do with political correctness or any moral and/or political danger. I'm with Gould on this one. If the evolutionary psychologists are correct then so be it. We live with the consequences of good science no matter how uncomfortable that makes us.

    I object to the science. I don't think it's correct, for example, to postulate that we have a gene for homophobia and to make up a just-so story to explain how it could have been selected in our ancestors. I don't think it's correct to imagine that we all have a gene for "religion" and then to make up a story about how it could have been beneficial in a primitive hunter-gatherer society.

    I object to those scenarios for two reasons. First, I don't think there's any such thing as a gene for "religion" or "homophobia." Or for most other behaviors, for that matter. Second, I don't think natural selection is anywhere near powerful enough to do what's demanded of it.

    These are the same problems that arise with most adaptationist just-so stories. If natural selection were as potent as the adaptationists claim in their stories, then you have to wonder why we still have wisdom teeth, susceptibility to malaria, and women dying in childbirth.

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  45. Sorry, but I feel you are just wiping your ass with the fact of the fetal distribution of hair. If retaining hair on the top of the head is the result of the shaping force of directional selection, you imply the fact this trait is preshaped in the chimpanzee fetus is just a bizarre coincidence.

    "If hairlessness arose in a single mutation (and not as a selectively neutral pleiotropic effect of a gene responsible for another trait that does enjoy a selective advantage) and increases in frequency - but not intensity - due to natural selection, it is still an adaptation".

    I never said it could not be an adaptation, but here selection only affects fequency, and not the organic change itself at the origin of the trait. This is a little bit hard for panselectionists to understand, but "adaptation" or "selectively advantageous" is not equal to saying "shaped by selection". Selection in such cases is more a grid or restriction rather than the "ceramist" that Dawkins would like it to be.
    One of the interesting consequences is that indeed, a one-step trait needs no selection to originate OR EXIST and can be imposed in a population by drift rather than selection. We can tire of providing examples of such cases. Traits can exists neutrally; they may become adaptations therafter, but selection is not a requisitie for origin of the trait and though it may help to maintain the trait, that is not necessarily the case, since drift can have that same effect.

    A reccomendation: complex traits do not imply that the parts of them must have been shaped by selection. Nor do complex adaptations constitute in themselves evidence for selection shaping an adaptation. Complex adaptations more often are the accumulation of macroevolution, with lots of exaptation involved and innovations spread out in time. Just pointing to a complex adaptaion with the finger and saying it is in itself evidence for the power of natural selection to shape adaptation is XIXth century darwinist ideology; not evolutionary science.

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  46. "If leglessness arose in a lizard from a single gene mutation, and that trait becomes universal throughout a population and ultimately a species due to positive selection, would you argue that leglessness in this species is not an adaptation?"

    No, I'd say that the origin of this adaptaion has more to do with mutation and development than with natural selection.

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  47. "Reeve, HK and PW Sherman, 1993: "An adaptation is a phenotypic variant that results in the highest fitness among a specified set of variants in a given environment."

    This "compoetitive" definiton is clearly deficient. For instance, "having eyes" is no doubt an adaptation for humans, but we all have eyes and eyes do not determine fitness differences. Therefore, according to the defintion above, having eyes is not an adaptation in humans.

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  48. You know, I think I’ve discovered the core of your argument: there are some things that *you* have decided are not (politically) "correct" and that should not be studied. But instead of being upfront about it, you are *framing* this issue as being about the proper methodological approach that should be employed when doing science.

    It leads you to ridicule a scientist over a non-controversial issue (Dr. Hotopp) for proposing a hypothesis that will lead her or others to investigate further. Show me a reputable scientist that believes that merely proposing hypothesis that you call a just-so-story is proof of that hypothesis?

    Larry Moran: "I object to those scenarios for two reasons. First, I don't think there's any such thing as a gene for "religion" or "homophobia." Or for most other behaviors, for that matter. Second, I don't think natural selection is anywhere near powerful enough to do what's demanded of it."

    That fine. But does what you believe mean that even those that don’t agree (and even those that might be trying to determine the inclusiveness of your category of “most other behaviors”) should be prevented from pursuing their inquiry? Or that they should be publicly ridiculed while they do it?

    Larry Moran: "Those of us who object to the excesses of sociobiology ..."

    The attack on Sociobiology started when Sociobiology was in its infancy. It was a *overt* *political* attempt to stifle scientific inquiry before it even got started. There were no “excesses” to object to, other than the audacity of hypothesizing that human behavior might have a genetic basis analogous to the well documented situation in “lower” species.

    Larry Moran: "I'm with Gould on this one. If the evolutionary psychologists are correct then so be it. We live with the consequences of good science no matter how uncomfortable that makes us."

    Well then (with all due respect) let those interested in studying those things do just that, using whatever approach suits them. Wait for the data to settle the issue. Stop the shameful attempts to attack, ridicule, and intimidate honest and decent scientists pursuing their investigations where they lead.

    Gould’s association with the anti-sociobiology movement was not the most distinguished moment in his illustrious career, and he acquiesced (at the very least) in a political movement to prevent legitimate inquiry that used tactics of humiliation, intimidation, and threats of violence. “The Spandrels of San Marco” was (and remains) an important contribution to the field of evolutionary biology, but it was also a very political document that was used in a very political way to support a political movement.

    Larry: "I don't think it's correct to imagine that we all have a gene for "religion" and then to make up a story about how it could have been beneficial in a primitive hunter-gatherer society."

    If that "story" is actually a testable hypothesis, why not? You seem to be attacking a core strategy of the scientific method (hypothesis generation) and attempting to distinguish it on the basis of its underlying assumption. And should what you think is "correct to imagine" determine what others should imagine in the course of pursuing their work?

    Larry Moran: "I object to the science. I don't think it's *correct*, for example, to postulate that we have a gene for [eye color] and to make up a just-so story to explain how it could have been selected in our ancestors."

    I substituted the politically charged trait [homophobia] for something politically neutral. I disagree with your statement, if what you call (frame!) as a "just-so" story (and which the scientist would call a "hypothesis") is useful for guiding their inquiry. (And I think "eye color" is neutral, but if the neutrality of that characteristic is important in determining who gets ridiculed and who does not, then who makes that call?)

    Larry Moran: "These are the same problems that arise with most adaptationist just-so stories. If natural selection were as potent as the adaptationists claim in their stories, then you have to wonder why we still have wisdom teeth, susceptibility to malaria, and women dying in childbirth."

    Again, more strawman attributes. Find me the biologist who believes that absolutely all characteristics must be adaptations, who believes that all species are at the pinnacle of fitness, and that nothing can possible be a relic. (Come on now, I want actual names. Don’t quote mine others, nor cite the opinion of someone who wrote a book.) Again, I think you are failing to distinguish between someone who treats adaptation as a default assumption for the purpose of generating testable hypotheses to focus further investigation, and the strawman who thinks adaptation can explain it all (and that a hypothesis is proof).

    Divalent

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  49. "the origin of this adaptation has more to do with mutation and development than with natural selection"
    What could this possibly mean? The "origin" of ALL phenotypic traits MUST be traceable, proximately to mutation and development...how could it be otherwise? This is almost as vacuous a statement as "Evolution is about what is possible, not about what is..."better"." which, as I parse it, means only that the impossible is not possible.
    Somebody mentioned Tinbergen's four questions (basically physiological mechanism, developmental mechanism, ultimate origin, and current utility), and I think those distinctions are being lost in much of this discussion.
    I also suspect that we are using various definitions of "adaptation." I confess I do not understand the difference being drawn between "shaped by selection" and...whatever the alternative is supposed to be. The Sherman/Reeves current-utility definition is about the maintenance of phenotypes in current (and recent) environments, and thus includes traits that "pluralists" want to split off as "exaptations." If you insist that a True Adaptation must have been favored from its very first appearance (through mutation and development, there are no alternatives unless you really are Lamarkian) by selection pressures identical to those that maintain it today, then you have set the bar at nearly unjumpable heights in the absence of a good time machine (we can get clues from mapping phenotypes and environments onto phylogenies, but there are of course serious problems with recovering a correct and complete full phylogeny).
    Please understand that I do not believe that every single visible phenotype must be an adaptation. Nor do I believe that adaptation = perfection (that's panglossian). I can't speak for evopsychists (some of their excesses seem silly to me too) or people like Dennett, but no biologist does--not even Dawkins (one of his chapter titles, I think in Extended Phenotype, is "Constraints on perfection"). But look...arguments from personal incredulity do not change the fact that selection is, in fact, very powerful over longish time periods. This statement is defendable both theoretically (population genetics) and empirically. It is also a fact that adaptation, very generally (i.e. a match between organisms and environments), is itself empirical. Further, phenotypes are, in fact, "exposed to selection." I therefore find the hypothesis that a population-fixed phenotype is adaptive far more compelling, as a working hypothesis if nothing else, than a big hyperpluralist shrug ("well it could be drift! or neoteny! or, uh, something, you know, pluralistic!"). This is not just-so-storytelling, it's reasonable hypothesizing based on prior knowledge. I too want to see some data before I am willing to call a phenotype adaptive with certainty. But to me, there is just as large a burden of proof on the contention (for example) that a phenotype is fixed by drift: i.e., selective neutrality or near-neutrality plus small effective population size.
    Judging adaptive hypotheses as "silly just-so stories" is entirely subjective, equally subjective (maybe moreso), and undefendable, as a prior assumption that every trait must be adaptive.
    As for Dr. Moran's list of examples (which have in common, as far as I can tell, only his personal incredulity), it's a little ironic that he is asking me to provide speculative adaptive stories for them. I won't, though I bet I could, and yes, some of my stories would seem (or be) silly. Note that most of them are examples of traits that, empirically, vary among humans (not fixed), and therefore do require explanation (even if it's just recency, or drift). I will say that it's important to distinguish between traits that vary within populations (ABO blood types, tongue-rolling, foot size) and those that are highly correlated to ancestral geography and more-or-less fixed within populations (skin color, lip size, eye folds, hair quality). (These are not, of course, mutually exclusive alternatives, as illustrated by the ABO locus.) For alleles that are associated with the former, the likely hypotheses are a) near-neutrality + drift + (probably) recency of origin and/or gene flow, b) frequency-dependent selection, and c) heterozygote advantage. In the case of ABO, I again claim that its very long persistence as a polymorphism is evidence (not, of course, "proof") for a or b. For geographic ("racial") variation, the first-call hypotheses would be a) near-neutrality + drift (including, probably, a founder or bottleneck effect), b) natural selection, or c) sexual selection. Variation in skin color, for example, is very likely to have an adaptive explanation, at least in part. For much of the rest, I'd join Darwin, Diamond, and Dawkins in plumping for sexual selection.
    One more point, and then I really mst quit this more-or-less pointless argument. I mean this to be provocative. It seems to me that the knee-jerk antiadaptationist "pluralists" are quite likely to be biochemists (Moran), geneticists (Lewontin) or paleo-types (Gould and, I gather, sanders). People who study real organisms living in real environments are far more likely to be "adaptationists." Why might that be?
    p.s. what Divalent just said.

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  50. Divalent says,

    You know, I think I’ve discovered the core of your argument: there are some things that *you* have decided are not (politically) "correct" and that should not be studied. But instead of being upfront about it, you are *framing* this issue as being about the proper methodological approach that should be employed when doing science.

    We're not going to get very far in this discussion if you keep trying to put words in my mouth.

    I have never, ever, said that there are things that shouldn't be studied. I have argued in the past that we should study many things that are not "politically correct." Please don't make that statement again or this discussion is ended.

    What I've said is close to the second part of your sentence. I have an strong opinion about how things should be studied and I have a strong opinion about how evolution occurs. In my opinion it is not good science to assume your mechanism (natural selection) when developing explanations for a given feature. The very first question you need to ask is whether the feature is an adaptation. If you decide to rule out all other possible mechanisms of evolution then you should explain how you arrived at this conclusion. When you jump right into an adaptationist just-so story you are revealing a bias. You might also be revealing a lack of knowledge of how evolution really works.

    With regard to the word "framing," I think you know that to me framing is just another word for "spin." Spin is something you do deliberately in order to twist the argument in a certan direction. When you "spin" something you are making a conscious effort to deceive or mislead.

    I don't spin and I don't frame. You may not like what I'm saying but at least accord me the courtesy of accepting that I'm sincere about it. I accept that you are sincere about defending the adaptationist program and I don't insult you by attributing ulterior non-scientific motives.

    It leads you to ridicule a scientist over a non-controversial issue (Dr. Hotopp) for proposing a hypothesis that will lead her or others to investigate further.

    Her "hypothesis" is that the extra DNA must be an adaptation. That doesn't sound like a question to be. It sounds like her mind is already made up. A scientifically correct hypothesis would be something like: "I propose that the extra DNA confers some fitness advantage on the individuals that possess it."

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  51. sanders: "we all have eyes and eyes do not determine fitness differences."

    Do you wish to argue that there is no such thing as congenital blindness (or more narrowly, genetically determined congenital absence of eyes)? And that this has no effect on fitness?

    "you imply the fact this trait is preshaped in the chimpanzee fetus is just a bizarre coincidence."

    This is a strange misinterpretation of my views.

    As Sven DiMilo suggested, review what Tinbergen wrote about the "four questions," in order to avoid the elementary mistake of conflating levels of explanation and hence erroneously concluding that they are mutually exclusive.
    http://en.wikipedia.org/wiki/Tinbergen%27s_four_questions

    Also see:

    Gerhart, J and M Kirschner. 1997. Cells, Embryos, and Evolution.

    Gilbert, SF. 2001. Ecological developmental biology. Developmental Biology. 233:1-12.

    Pigliucci, M and J Kaplan. 2000. The fall and rise of Dr Pangloss: adaptationism and the Spandrels paper 20 years later. Trends in Evolution & Ecology. 15:66-70

    Williams, GC. 1992. Natural Selection: Domains, Levels, and Challenges.

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  52. This comment has been removed by the author.

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  53. You take the fetal pattern lightly. Have I ever ruled out the possibility that this hair pattern is adaptive for humans as in the "run in the sun hypothesis"?
    You fail to recognize that "adaptive for running in the sun" is not equivalent to "shaped by selection for running in the sun". The hair pattern apeared in the fetus, and thereafter in adult, making "run in the sun" suddenly possible.

    You gradualist scenario that attributes this pattern to selection would indeed imply that the fetal pattern is nothing but a coincidence.

    If you do not understand this...there is little hope.

    I would not call ANY trait with an effect on fitness an "adaptation".I think most people understand that for a trait to be adaptation it must have a positive effect on fitness; that is, a novelty that is favored by selection, not eliminated by it as in the cases you propose. I think you've got it all quite wrong.

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  54. sanders: "that attributes this pattern to selection"

    No, I attributed relative hairlessness, not the spatial distribution of hair, to selection. Reread my comments.

    Based on the above and other remarks, I have to conclude that the main issue here is your repeated misinterpretation of my statements, for whatever reason.

    The problem with many pluralists (structuralists, Gouldians, whatever they want to call themselves) is that they believe they are exhibiting sophistication simply by hand-waving about developmental constraints, bricolage, systems theory, exaptations, L-systems etc. Rest assured that we adaptationists are aware of these things as well. I daresay that modern adaptationists tend to have a more sophisticated understanding of the interplay of these phenomena with selection and other evolutionary forces (yes, Dr. Moran, including drift) to shape organismal form and function.

    Too many pluralists fail to understand that some of their favored default nonadaptationist assumptions are no less fanciful and unsupported than some adaptationist ones. All hypotheses have to be subjected to testing.

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  55. ha, I thought you KNEW it, but you don't. The "run in the sun" hypothesis emphasizes how having hair on the top of the head, but not on the rest of the body, is ideal to prevt solar radiation at the head, while allowing the rest of the body to lose heat.
    IYet you try to pretend that you are discussing completely unrelated trait...well that's just stupid.

    Other than that you can make as many non-biological and frivolous "closing statements" about pluralists and adaptationists as you wish. Come back when you have something truly interesting.

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  56. I think a substantial part, if not the majority, of paleo people, biochemists etc. are adaptationists. let's face it, it's pretty easy to understand, kinda a default condition.
    If objectors arise more notoriously in paleo or biochemical fields, gee, I don't know..maybe we just have greater intellectual diversity than the typical row of "darwinian ecologists".
    But of course there also are "neutralists" ecologists too like Hubbell, S. P. (2001). "The unified neutral theory of biodiversity and biogeography."

    Anyway, it intrigues me that ALWAYS adaptaionists come u with tehse frivolous, silly, gossipy arguments. Guys, only reatrds will buy that crap. You know, people who will be willing to judge on appereances rather than true arguments.

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  57. "I confess I do not understand the difference being drawn between "shaped by selection" and...whatever the alternative is supposed to be"

    yeah...well make it pretty clear that you don't really care about understanding.

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  58. Sanders, show me where in "Endurance running and the evolution of Homo" by Bramble and Lieberman (Nature. 432:345-352. 2004.) they bring up scalp hair. ("Cranial cooling systems" refers to cranial venous circulation.)

    And look which notorious ultra-adaptationist provisionally accepted the Lieberman-Bramble hypothesis as worthwhile and not a candidate for immediate dismissal as one of those baseless just-so stories.
    http://pharyngula.org/index/weblog/comments/marathon_man/

    At least Sanders has done us the service of demonstrating that snideness is no substitute for argumentation.

    The post started out with, and much of the thread has followed, a contrast between the allegedly sophisticated global neoteny epiphenomenal hypothesis of human hairlessless and the allegedly naive 'just-so story' of endurance running. At this point in the thread, how many of you think the former is much more scientifically rigorous and supportable than the latter? At the very least, how many think at this point that the running hypothesis ought to be dismissed out of hand?

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  59. There is an older study that photgraphed bipedal models form different sun-angles, measured the areas "exposed" in each photgraph and concluded that the head was most exposed and related this to hair distribution.

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  60. I have been hearing about these hot-running ape hypotheses for years now, in relation to bipedism, AND the distribution of hair. I completely agree that this hair distribution can be good for running in the sun. I have not once called this a bad speculation or a just-so-story. I stated at the beggining of this thread that I object to the "just so story" pejorative because it's unspecific and unfair.

    But the hair distribution pattern is a pretty straightforward neotenic trait. A I said, this was already present in the fetus, long before sun-running. If you ask me, the neoteny of this trait helped make "run in the sun" possible. In THAT order, OK? THAT is what is consistent with the datum of the chimpanzee fetus, a truly integrative approach to ALL the information.

    But for an adapataionists, current adapative advatages of this hair diostribution for sun-running contain in thmesleves the evolutionary explanation for its origin. Moreover you have expressed your preference for a gradualist scenario of directional selection as "more likely",you actually mean the fetal pattern could well have not existed: that it has no true importance.

    If you do not think this, I think the burden is on you to PLEASE explain to us HOW do you think the chimpanzee fetal pattern was relevant at all for the origin of this adaptation.

    Because right now, you seem to be pushing this datum off the table. Being speculative withotu much evidence is not so bad; denying the relevance of data that is dangling in front of your eyes..,. well that's the kind of silly thing only intellectual alienation can achieve.

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  61. Sanders: "But the hair distribution pattern is a pretty straightforward neotenic trait."

    I agree that it is an apparently pedomorphic trait.

    To quote myself:

    "Selection acts on variants of developmental programs that have been shaped over their phylogenetic histories by a variety of evolutionary forces."

    Just to make sure that we are on the same page: You're speculating that the pedomorphic hair distribution pattern appeared first (as a developmentally constrained side effect of another process?) and it was permissive for "run in the sun."

    In contrast, in my model, the "run in the sun" behavior emerges first, which results in selection for hair loss - and hence the pedomorphic hair distribution pattern (whether it emerges gradually or full blown) undergoes positive selection and is reinforced and modified. Selection for general hairlessness would act on the developmental pathway of body hair emergence and so produce a pedomorphic distribution pattern, (unless there were selection for total hairlessness, which obviously there wasn't).

    Example of modification: ever-growing head hair.
    http://mednews.wustl.edu/tips/page/normal/4405.html

    (It's conceptually possible that the chimpanzee fetal hair distribution pattern is a spurious non-homologous similarity and the adult human hair pattern arose independently through the strong selective advantage of having thick head hair on a mostly denuded body. But I doubt it. It's far more plausible - and parsimonious - that selection made use of a preexisting developmental program.)

    The facilitating effect of the hairlessness with its (pedomorphic) distribution, along with the rest of the functional trait complex (anatomical, physiological) on "run in the sun" behavior provided a positive feedback loop of behavior, selection, and trait complex.

    Note that acknowledging the pedomorphic nature of hair distribution does not in any way constitute an endorsement of Gould's epiphenomenal global neotenization model.

    We agree that heterochrony can be highly modularized.

    Another hypothesis for hairlessness: defense against ectoparasites
    http://tinyurl.com/2vvfal

    Maybe the actual scenario was more complex than current models and included multiple selective forces acting on differentially developmentally linked traits (hormone activity etc.), perhaps even involving genetic assimilation. I am not personally invested in any particular model.

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  62. In a topic like this, where any source of information is of great value, I find it revealing that one of the few compelling pieces of data that is available becomes inevitably downplayed by an adaptationist viewpoint.

    "You're speculating that the pedomorphic hair distribution pattern appeared first (as a developmentally constrained side effect of another process?) and it was permissive for "run in the sun."

    It appeared before running in the sun, as the chimpanzee fetus shows. Why do you call this a speculation? The organism was capable of producing this hair pattern long before running in the sun.
    Whe the trait appeard in the adult, running may have already being in place, but it may have perfectly well not, either. We don't know. However I think that there is no way that acquiring that pattern in the adult did not radically improve the running in the sun, opening a wider range of behavioral possibilities.

    Anyhow, it is good that you acknowledge that there is a feedback between behaviour and selection; maybe you will see that this cyclical dynamic of interactions between behaviour, trait and selection does not allow a reduction only to the selective component.
    I wonder why did you not mention development though. It is not putty, you know.

    "Selection for general hairlessness would act on the developmental pathway of body hair emergence and so produce a pedomorphic distribution pattern, (unless there were selection for total hairlessness, which obviously there wasn't)"

    But selection would not affect the establishment of the hair pattern, but merely delay the presence of that pattern into the adult. It would be a "timing" mutation: not a "patterning" one.

    I am trying to use this example to make you reflect on what the importance of things other than "current use" can have in the origin of adaptations. Do you really think without this preexisting fetal pattern humans would have anyhow evolved running in the sun? Well, I guess that there is where we can draw a clear line between our views.

    "and hence the pedomorphic hair distribution pattern (whether it emerges gradually or full blown) undergoes positive selection and is reinforced and modified"

    How is it reinforced and modified by selection if it had emerged "full blown"? Face it; if an adaptive trait emerges full-blown, selection can maintain it but has little to do with its origin. This origin will have a much more to do with developmental possibilities than with the result of directional selection.

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  63. Sanders: "It appeared before running in the sun, as the chimpanzee fetus shows."

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  64. I hit the wrong button and published prematurely.

    Sanders: "It appeared before running in the sun, as the chimpanzee fetus shows."

    That's right - in the FETAL stage, not the adult.

    Sanders: "How is it reinforced and modified by selection if it had emerged "full blown"?"

    Are you prepared to argue that the human adult hair distribution pattern has complete fidelity to the chimp fetal pattern? That there has not been the slightest developmental modification? ("Full blown" refers to the generic hairy scalp-denuded body pattern, not is precise manifestation today. Hence there is room for modification.)

    Sanders: "...does not allow a reduction only to the selective component."
    "...on what the importance of things other than "current use" can have in the origin of adaptations."

    One more time (with new emphases):

    Me, earlier post: "Selection acts on variants of DEVELOPMENTAL programs that have been shaped over their phylogenetic histories by a VARIETY of evolutionary forces."

    There is little point in us continuing this argument. We have acknowledged our respective differences and similarities on this topic. (Except where you insist on seeing differences where none exist.)

    We're all adaptationists and we're all pluralists. Me, you, Larry Moran, Richard Dawkins, Richard Lewontin, Stuart Kauffman. Sure, we have different emphases, different perspectives. On a conciliatory note, let me suggest that the existence of multiple approaches is conducive to the advancement of evolutionary science, and not a pathological rift.

    Despite misunderstandings, you've made some cogent points, as well as some that are perhaps less well considered. Anyway, I wish for the success of your endeavors.

    - "Anonymous"

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  65. ""Full blown" refers to the generic hairy scalp-denuded body pattern, not is precise manifestation today. Hence there is room for modification"

    Pfffft. I hope you realize It's pretty annoying to discuss with you acting like this. That pattern is the adpataion we are discussing. Period. Don't try moving goalpoasts again like that, it is very non-elegant.

    Human skin evolution has painfully few sources of information; but uite beyond this specific case, I bring to your attention once more that any one-step origin of an adaptation (which are wel-documented) cannot be said to be the result of directional selection. This is no divagation of mine: it is the CLASSICAL antidarwinian argument of the mutaionists: De Vries, Bateson, Goldschmidt. And it's alive and kicking. All of them emphasized development.

    Anybody should understand this point clearly. When adaptaionists say they don't understand, they seem to me simply unwilling to understand.

    I wih you luck too in your future reserach, I think you will be needing it because the study of the origin of adaptaions in the wild and in experimental evolution, where genes are studied at the molecular level of resolution, has shown few mutations with large effect are behing the origin of new adaptations. In fact, there is no example that I know of where an adaptation has been shown to be have been shaped by and accumulation of several gnes by natural selection.

    If you have any such case, please present it.

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  66. I should probably should let this be a sleeping dog, but I want to make (or re-make) a couple of points, if only because sanders has been such a dick about it.
    a) Whether a trait (say, the hairiness of human bodies) originates by many small mutations, each one favored by selection (I think this is what is meant by "shaped by selection," but I'm not sure..not because I don't want to understand but because the phrase keeps getting used without definition or explanation), or, alternatively, by a single mutation of large effect (e.g., "full-blown" pedomorphosis) makes absolutely no difference in terms of whether or not it should be considered an "adaptation." Therefore this: "any one-step origin of an adaptation (which are wel-documented) cannot be said to be the result of directional selection" is just plain Wrong. To argue otherwise is to ignore a huge literature on the concept of adaptation (e.g., Rose & Lauder (eds.), 1996, Adaptation; G.C. Williams's books).
    Again: Tinbergen's four questions...there's four of them, see, because they're different questions.
    2. It still seems to me that explaining a phenotype as resulting from drift, or developmental constraint, or heterochrony, or whatever makes pluralists more happy, carries at least the same burden of proof as attributing it to selection.
    3. Any hypothesis of origin and/or maintenance of a particular phenotypic trait is legitimate if it can be tested, even "silly just-so stories." And you know what? it's OK to suggest hypotheses even without testing them right away, and even if testing them would be difficult or impossible, if they are stated as hypotheses. The naive adaptationism that suggests a possible adaptive value to a trait and then considers the matter closed and settled is indefensible, but so, equally, is an argument like "oh, it seems likely to be neotenic so no adaptive explanation is necessary," and leaving it at that.
    4. Read G.C. Williams. He makes the point that the adaptationist program applied to (fixed) phenotypes of extant populations is about maintenance of the phenotype in the face of ongoing mutation, geneflow, and drift, not so much telling tales of evolutionary origins; thus, modern adaptationism is more about explaining the absence of evolution.
    5. Related to the above, "neoteny" is not a sufficient explanation for the persistence of human hairlessness. Neoteny plus fitness-neutrality plus drift would be; neoteny plus population bottleneck would be; neoteny plus selection would be.
    Open any comparative physiology text and learn about the effect of pelage on mammalian energy budgets and the third explanation emerges as the most likely. It really does.
    6. Adaptation is empirical. There really are a gazilliion examples of phenotype/environment matching which even the most ardent pluralist would be foolish not to accept as adaptations. I therefore repeat: in a world of nails, why insist on trying screwdrivers, reciprocal saws, and jackhammers before reaching for the trusty hammer? This attitude I just don't get. But then, I study organisms, not sequences or rocks.
    7. I am unable to find any reference to the presence of pubic and axillary hair in chimp fetuses, only that (as in humans) the hair on top of the head is the first to begin growing. I'd be interested if anyone knows of such. In the meantime I'll continue to regard the Gould quote as stupid (in that regard).
    8. Geographic differences in relative body-hairiness among humans, combined with the marked sexual dimorphism within all populations, are strong clues that sexual selection was involved somehow in the origin and/or maintenance of the hairless phenotype. This is by no means mutually exclusive with natural selection (for running, antiparasitism, or whatever), and not even exclusive with an (otherwise) neutral/drift scenario (which I doubt for other reasons, above).
    And now I really will shut up...classes start Tuesday and there is much work to be done.

    p.s. re: "there is no example that I know of where an adaptation has been shown to be have been shaped by and accumulation of several gnes by natural selection."
    Very "pluralistic" of you.

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  67. JEeez!! Calm down, buddy. There is too much anti-structuralist resentment there to answer; you are not talking to ME, that's clear. I never said adaptaion does not exist, I never said adaptive hypotheses are intrisically silly or speculative. We all agree on the importance of adaptation.
    Plus, quite honestly, I think you are making a little bit of a chauvinsitic fool of yourself.

    What we don't agree, quite plainly, is that you backwardly think that adaptation=shaped by selection.
    And all i did was to ask you for an example where a new trait has clearly been shaped by the accumulative effect of directional natural selection.

    I'd even be happy with an example where there is yet no molecular resolution. Orr says the cases proposed by Dozhansky, Huxley, etc are in retrospective "apallingly weak". I want to know if I agree, but I juts haven't found where these authors refer to these cases...

    But then, Sven,,...are you really understanding what we are talking about here?

    One has to wonder...

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  68. "But then, I study organisms, not sequences or rocks"

    You mean you study ONLY organisms: no sequences or rocks.

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  69. Sanders says: "Chimpanzee fetuses have hair on the head, armpits and genitals only."

    Like Sven I can't find anything in the literature about this, but I'm not an anatomist so I may be looking in the wrong place. Chimp fetuses do indeed develop hair on their heads, but armpits and genitals?

    Sanders, could you please supply a reference for your claim.

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  70. I guess I must have read it years ago in "ontogeny and phylogeny", but I dont have it with. If anyone can look it up he may correct me if I am wrong or misunderstood something. I have at least remembered restriction to the head accurately, which is the bit relevant to our discussion.

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  71. But, I bet I'm right....I think I have read elsewhere more recently too...

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  72. Dears,

    Could you please tell me if the "founder effect" (= population bootlenecks?) can preserve non-adaptative features?

    If so, in this case, it would be interesting separate the concept of fitness from the usual definition (fitness = frequency in the population at generation t+1 divided by frequency in the population at generation t.

    That is, I would like to be able to say that a low fitness gene are preserved and propagated due to a founder effect. Is this correct?

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  73. "If the hairlessness of the foetal ape was being retained into
    adulthood by a process of neoteny, one would expect the
    human body to retain this characteristic throughout its
    whole development from embryo to adult. However, this is
    not the case. When the human foetus is 6 months old, it
    becomes completely covered with a coat of fine hair known
    as lanugo. Normally, this hair is shed long before birth;
    occasionally, a baby is born still wearing its woolly coat,
    only to lose it within the first days after birth (Morgan,
    1982).
    Another weakness of the theory is that while some
    characteristics may be retained as part of a neotenic package,
    this only applies to characteristics that are either benign
    or neutral in their effect on fitness to survive. No one claims
    that all foetal characteristics are retained in a neotenic
    species. For example, a human foetus and a human baby
    both have very short bandy legs, but natural selection
    ensures that this feature is not retained in adult life (Morgan,
    1990). Furthermore, the neoteny theory does not tell us
    anything about the value of nudity as a new character that
    helped the naked ape to survive better in his hostile environment
    (Morris, 1967)." Rantala, 2007

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  74. "aquatic ape just-so story"??
    I agree "aquatic ape" is inaccurate, "ape" should be "Homo" and "littoral" is more precise then "aquatic", but the "littoral theory" appears to be correct: early-Pleistocene Homo did not run over open plains as the conservative story wants, but simply followed coasts & rivers. This didn't happen in 5 or 10 Ma, as Elaine Morgan thought, but in the Pleistocene.
    Human Evolution publishes in 2 special editions the proceedings of the symposium with Don Johanson & David Attenborough on human waterside evolution "Human Evolution: Past, Present & Future" in London 8-10 May 2013:
    Special Edition Part 1 (end 2013)
    - Peter Rhys-Evans: Introduction
    - Stephen Oppenheimer: Human's Association with Water Bodies: the 'Exaggerated Diving Reflex' and its Relationship with the Evolutionary Allometry of Human Pelvic and Brain Sizes
    - JH Langdon: Human Ecological Breadth: Why Neither Savanna nor Aquatic Hypotheses can Hold Water
    - Stephen Munro: Endurance Running versus Underwater Foraging: an Anatomical and Palaeoecological Perspective
    - Algis Kuliukas: Wading Hypotheses of the Origin of Human Bipedalism
    - Marc Verhaegen: The Aquatic Ape Evolves: Common Misconceptions and Unproven Assumptions about the So-Called Aquatic Ape Hypothesis
    - CL Broadhurst & Michael Crawford: The Epigenetic Emergence of Culture at the Coastline: Interaction of Genes, Nutrition, Environment and Demography
    Special Edition Part 2 (begin 2014) with 12 contributions.
    FYI, google
    -econiche Homo
    -Greg Laden misconceptions Verhaegen
    -Vaneechoutte Rhys Evans


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