Category Archives: Biology

Humans are the only animals that …

When I saw this tweet by Ed Yong, I had to smile:

… because it reminded me of a quote I love from Daniel Gilbert’s awesome book Stumbling on Happiness:

Priests vow to remain celibate, physicians vow to do no harm, and letter carriers vow to swiftly complete their appointed rounds despite snow, sleet, and split infinitives. Few people realize that psychologists also take a vow, promising that at some point in their professional lives they will publish a book, a chapter, or at least an article that contains this sentence: “The human being is the only animal that . . .” We are allowed to finish the sentence any way we like, of course, but it has to start with those eight words. Most of us wait until relatively late in our careers to fulfill this solemn obligation because we know that successive generations of psychologists will ignore all the other words that we managed to pack into a lifetime of well-intentioned scholarship and remember us mainly for how we finished The Sentence. We also know that the worse we do, the better we will be remembered. For instance, those psychologists who finished The Sentence with “can use language” were particularly well remembered when chimpanzees were taught to communicate with hand signs. And when researchers discovered that chimps in the wild use sticks to extract tasty termites from their mounds (and to bash one another over the head now and then), the world suddenly remembered the full name and mailing address of every psychologist who had ever finished The Sentence with “uses tools.” So it is for good reason that most psychologists put off completing The Sentence for as long as they can, hoping that if they wait long enough, they just might die in time to avoid being publicly humiliated by a monkey.

Of course, he writes this just before going on to put his own Sentence in print for everyone to see, but with an introduction like this I’ll cut him some slack.  Perhaps one day I’ll write The Sentence myself…

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What is an animal’s “choice”?

Image by loryresearchgroup

In behavioural ecology, we face a number of limitations in trying to ferret out the relationship between behaviour and evolutionary forces.  These range from the philosophical and theoretical (e.g. what makes a behaviour adaptive or an adaptation?) to the mundane and methodological (is that experimental set up really measuring aggressive behaviour?), and solving these problems is one of the most pressing tasks facing a behavioural ecologist attempting to make useful statements about a behaviour’s evolution.  However, while some of these issues are recurrent and obvious, others are more subtle and can sometimes slip under the radar.  One such problem is the topic of a recent paper by Véronique Martel and Guy Bovin, published recently in the Journal of Insect Behaviour and entitled “Do choice tests really test choice?”  (DOI: 10.1007/s10905-011-9257-9).

The thrust of their argument is that there is a difference between “apparent choice”, and “true choice”, which is driven largely by the fact that we can’t ask animals what they would have done under different circumstances.  As Martel and Bovin point out, animals may make one choice when presented with a particular set of stimuli, or resources as they call it (which may mimic natural conditions!), but express a different preference when presented with a larger set of resources, or when the conditions of the choice are changed.  They distinguish three characteristics of a true choice, only one of which is met by an apparent choice:

  1. The choice must be non-random, i.e. that individuals must choose one resource more often than the others;  testing only this criteria means that researchers are measuring apparent choice, while this is a necessary but not sufficient criteria for true choice.  (I would add to this that the choice probability should be fairly stable if the animal is made to choose under exactly the same conditions).
  2. The choice should be the same even in the “absence of a differential response by the resource” (p. 332). The authors state this to avoid situations in which the resource (e.g. a potential mate) is manipulating the choice of the focal animal, a problem which reminds me very much of the literature on animal signalling.
  3. It should be demonstrated that every resource is perceived, to avoid issues of sensory bias and the like.  It strikes me that this criterion will be hard to meet;  for example, if while testing mate choice the researcher tries to demonstrate a lack of bias by showing responses by the focal individual to each of the potential mates in isolation, how does that prove that one or more of the potential mates aren’t being ignored when the focal individual is given the choice between all of them?
As the authors state, meeting criterion 1 is sufficient for an apparent choice, but 2 and 3 are required for a true choice.  They spend the bulk of the rest of the paper giving examples of both apparent and true choice and elaborating the differences between the two.  It should be noted that they are not claiming that one type of methodology is “better” than the other;  in fact, they take pains to point out the pros and cons of both.  Here’s an example:

The importance of distinguishing between apparent and true choices depends on the objective of a study. If the objective is to establish which resources will be exploited under natural conditions, then the apparent choice is appropriate. If the experimenter wants to know which female will be mated by a male in a natural situation, then the results of this test (the apparent choice) will provide the answer. However, if the objective of the experiment is to establish the mechanisms of this choice, then it becomes important to look more closely at the results. If a male does not perceive a mated female as a resource because she does not produce sex pheromone, the male is thus inseminating virgin females as they are the only resource perceived. In this case, an apparent choice (the virgin female) is expressed, but this choice is the result of the non-perception of the mated female, which prevents this apparent choice from being a true choice. Measuring an apparent rather than a true choice does not remove the relevance of the test, but only modifies its interpretation. Consequently, it is important for the experimenter to state a clear question before identifying the adequate experimental setup to use.

I think that it’s important to mention here that the ideas expressed in this paper aren’t terribly groundbreaking;  a number of people ranging from economics to psychology to behavioural ecology have, at one time or another, made largely the same argument or a variation thereof (one example of a related problem is raised by a really smart guy, Jeffrey Stevens, in this book chapter here).  In fact, I’m a co-author on a paper currently in press at Behavioural Ecology talking about this issue from the opposite direction, wherein we argue that the mechanisms that underlie behaviour may be constrained and that these constraints need to be taken into account when assessing the evolution of behavioural outcomes[1].  I even made an argument very much like the one in this paper during my Ph.D. synthesis exam!

Having said that, I like the paper for its laser-like focus on raising awareness about a very specific part of animal behaviour and cognition that can seriously undercut the conclusions drawn from experimental or field work if the appropriate test isn’t matched to the hypothesis the researcher wishes to explore.  I suspect that their definition of apparent and true choices is incomplete and leaves out issues that will be hashed out in future papers, but if the journey of a thousand steps has to start somewhere, it’s not a terrible first stride.
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[1]. I’ll write more about this here when the paper is published.

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Got questions about inclusive fitness?

Over at his blog, Andrew Gelman briefly mentions the recent profile of E. O. Wilson in the Atlantic, and along the way mentions the dustup over inclusive fitness that I may have mentioned here before  (did I? It’s hard to remember).   At the end, he makes a throw-away comment which drove me nuts:

The article also discusses Wilson’s recent crusade against selfish-gene-style simplifications of human and animal nature. I’m with Wilson 100% on this one. “Two brothers or eight cousins” is a cute line but it doesn’t seem to come close to describing how species or societies work, and it’s always seemed a bit silly to me when people try to loop everything back to a selfish-gene story.

I’ve been trying to think of a similarly aggravating comment to make about statistics in return;  maybe “lies, damned lies, and statistics”?  “You can prove anything with statistics”?  “Bayesian statistics suck because I don’t understand where priors come from?”  It bugged me enough that I left this comment:

It doesn’t seem like you know much about inclusive fitness, a theory has been massively successful in evolutionary biology. Despite the odd and unsupported comments made by Nowak et al., it stands firm as a well-supported and useful body of theory. Here’s a link to the letter published in response to Nowak et al.’s original article, signed by 137 authors including most of the field’s brightest minds:

http://www.nature.com/nature/journal/v471/n7339/full/nature09831.html?WT.ec_id=NATURE-20110324

The appeal to authority doesn’t mean that they’re right, of course, but extraordinary claims require extraordinary evidence; Nowak et al. have done nothing but ignore the entire published literature on inclusive fitness spanning decades and comprised of hundreds if not thousands of studies, while proposing a mathematical model that adds nothing to our understanding beyond what current theory already provides.

I respect your work on statistics, have always enjoyed reading your blog, and your book (BDA) is sitting on my shelf right now, but your offhand comment above is uninformed and very aggravating; I’d like to deal with that aggravation by offering to assist you in understanding one of the most powerful explanatory mechanisms in evolutionary biology. The letter above provides a succinct summary of the evidence that Nowak et al. ignore, but it might be a bit much for a non-technical audience; I haven’t published directly in this field, but I do work in evolutionary biology and I should be able to answer any specific questions you may have if you would like to pose them. If I can’t answer them myself, I will find people who can.

I’m not going to go into a full blown recapitulation of inclusive fitness theory and then defend it, because I’d have to write several inconveniently long books to do so.  But since I made the offer over there, I’ll make it here too for any interested readers:  if you have questions burning you up about this whole “inclusive fitness” thing, ask them here in the comments and I will do my best to answer them for you.  And if I don’t know what the answer is, I’ll find it.  No question is too small, though I make no promises on how long or short my answers will be!

I’ll leave off with a quotation from a fantastic book by Andrew Bourke that I’m reading right now, Principles of Social Evolution:

Like any large and active field of investigation, the theoretical study of social evolution is not free from disagreements and unresolved issues (e.g. Taylor and Nowak, 2007; West et al. 2007a).  Paradoxically, while the potential richness of inclusive fitness theory as a general theory of social evolution is still underappreciated, the theory is sometimes perceived as an entrenched orthodoxy. A tendency therefore exists for iconoclastically-minded theoreticians to derive models of cooperation in novel ways and then announce them to be fundamental additions to existing theory (e.g. Killingback et al. 2006; Nowak 2006; Ohtsuki et al. 2006; Traulsen and Nowak 2006).  It is healthy for orthodoxies to be continually challenged by new theories and new data.  However, to date, these models have fallen short of true novelty, as other authors have shown that their results are capable of being derived from inclusive fitness theory (e.g. Grafen 2007a, 2007b; Lehmann et al. 2007a, 2007b; West et al. 2007a).  Indeed, inclusive fitness theory has a long history of successfully assimilating apparent challenges and alternatives (Grafen 1974; Queller 1992; Lehmann and Keller 2006a).  This is not surprising when one considers its deep foundations in the theory of natural selection.  Although it is premature to declare a consensus, a substantial body of opinion therefore holds that claims of fundamental extensions to inclusive fitness theory will have to be radically innovative, as well as robust, to be accepted as such (e.g. Lehmann and Keller 2006a; West et al. 2007a).  For all these reasons, Hamilton’s (1964) inclusive fitness theory will underpin the conceptual reasoning employed throughout this book (pp. 22-23).

 

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Death in the nest: trade-offs rule the day.

Underlying many research programs in biology is the meta question: why is there more than one type of X?  (In continuous form, why is there variation in X?)  This question recurs in many areas of animal behaviour, and indeed in the entirety of the study of evolution itself.  Some examples include:

  • Why do animals show variation in “personality” – why are some consistently more aggressive, more exploratory, bolder, etc.
  • Why are there more than one type of male that females select between?  Why are some “attractive” and others “unattractive” – why aren’t they all attractive? (Sexual selection).
  • If aggressive signals like roaring can make other animals give up a resource or back down from a fight, why don’t all animals use the aggressive signal?  Why is there variation in signal type when all animals should use the same signal, which would then lose all meaning and be ignored?
  • Why do some animals invest heavily in each offspring while others produce as many as they can and invest very little in each?
The general response to most of these questions hinges on the idea of a trade-off.  In its most basic form, a trade-off involves giving up one thing to get (or avoid) another.  In particular, animal behaviour often hinges on cost-benefit tradeoffs.  It is desirable to have some trait or perform some behaviour, but doing so may come with a cost if we have too much of the trait or perform the behaviour too often or at all.   Examples of this litter the pages of any textbook in the biological sciences, from molecular biology up to zoology and ecology;  in particular, we can begin to address the questions I listed above by appealing to trade-offs:
  • Some personality types, like aggressive or exploratory, can confer benefits – such as always winning fights or being the first to find food – but also come with costs – such as the injuries from always fighting or the cost of being eaten while you try to be the first to eat.  Some individuals will be willing to make this trade-off, others will not.
  • The answer to this question has filled entire bookshelves, but here’s one tiny example:  in 1975, Amotz Zahavi published a landmark paper proposing that attractive males are “handicapped”;  they willingly trade off the cost of the handicap for the increased number of matings of come with it.  Zahavi’s “handicap principle”  suggested that this was a reliable indicator of quality to females because only some males would have the required quality (be strong enough, fast enough, etc) to bear the cost of the handicap in order to reap the benefit.
  • One of the most well-known answers to this question began the field known as evolutionary game theory;  at the end of the 1970s, the tragic figure of George Price and the eminent John Maynard Smith answered the question by showing mathematically how frequency-dependence could lead to a trade-off between Hawks, who are aggressive, and Doves, who back down at the first sign of trouble;  when Hawks are extremely common, their aggression leads them into costly fights against each other, which reduces the benefit of aggressiveness and makes Dove-ish behaviour more attractive.  But when Doves are common, Hawks get immense benefit with no cost by bullying Doves around.  (There’s actually significant overlap between this point and the previous, but that’s a topic for another blog post!)
  • An entire branch of evolutionary biology, life history theory, deals with questions like this:  in the face of limited resources, how do individuals make choices about the timing and sequence of events in their life to maximize their fitness?

This general pattern underlies the story behind a neat new advance-access paper from the groups of Alex Kacelnik and Juan Reboreda that manages to give away the good stuff in the title:

Ros Gloag, Diego T. Tuero, Vanina D. Fiorini, Juan C. Reboreda, and Alex Kacelnik. The economics of nestmate killing in avian brood parasites: a provisions trade-off. Behavioral Ecology, 2011.

Here, the question of types and the answer of trade-offs arises in the context of brood parasitism.  Brood parasites are organisms – birds, fish, insects – that relieve themselves of the responsibility of parenthood by tricking other organisms into doing it for them.  In birds, this usually takes the form of brood parasites laying their eggs in other species’ nests, where the enterprising young tykes then pretend to be the offspring of the unlucky suckers who are to play host.  Brood parasites can be specialists that only parasitize the nests of a target host species (or small group of species); an example of this is village indigobirds, who generally parasitise fire-finches (and who also display an interesting mechanism where the young copy the songs of the host species).  Generalists, on the other hand, will parasitise a range of host species;  cowbirds, for instance, are generalists.  Brood parasites can also vary in whether they eliminate the other offspring of the host that they have colonized (nestmate killing) or whether they attempt to blend into the crowd (nestmate tolerant).  To make this more concrete, take a look at this short video showing a newly-hatched cuckoo ejecting a reed warbler chick from the host nest:

The paper I’m talking about here explores an interesting question about brood parasites, namely:  why are some brood parasites nestmate tolerant while others are nestmate killers? Gloag et al. propose a mathematical model that explains this in terms of a “provision trade-off”.  Host nestlings can help the newborn parasite by stimulating the host parents to bring more food than the parasite could solicit alone, and if the parasite can outcompete its nestmates for that additional food, then it does better to let them live.  Thus the trade-off:  when the host offspring increase the fitness of the parasite, it lets them stay, but otherwise it kills its flatmates.  Gloag et al. take the time to break this trade-off down into its constituent parts, namely (in their words, p. 2):

  • The total provisioning rate stimulated by the whole brood, and
  • The share of the provisions received by a parasite nestling.
The simple model they derive shows that when the ability of a parasite to stimulate food provisioning by the host parents is greater than its ability to compete for food with its nestmates, the parasite will do best if it is reared alone and the murder spree begins.  This relationship depends on the interaction between these two variables;  in other words, “[i]f each host nestling causes a greater increase in provisioning than the amount it consumes, then the presence of host chicks would result in higher consumption for the parasite, even if a host chick takes a bigger fraction of the extra food than the parasite.”  The model helps to predict where each scenario – nestmate killing or tolerance – is plausible as a function of this intuitive trade-off.
VIRA-BOSTA (Molothrus bonariensis)

VIRA-BOSTA (Molothrus bonariensis) by Dario Sanches, on Flickr

Gloag et al. then use this model to explain differences not only intra-specific differences between specialist species in their level of nestmate tolerance, but also inter-specific differences within generalist species as well.  This would have been a good paper even if they had stopped there, but they then go on to test their ideas in the field using a generalist parasite, the shiny cowbird (Molothrus bonariensis). Working in South America, they searched for the nests of two types of shiny cowbird hosts, chalk-browed mockingbirds and house wrens, and set up two experimental conditions.   In the “mixed group”, the a single cowbird egg was placed among host eggs, and in the “alone” group, the cowbird eggs were placed in the host nest with dummy eggs so that the cowbird young would be reared alone.  They measured the food amount and quality brought to the nest from video recordings, and measured the physical quality of the resulting offspring (weight and tarsus length).  They also compared the mortality rates of the cowbird chicks to see if there was a difference between the conditions.  Their findings?

In our field study, nestmate tolerant shiny cowbirds encountered both sides of a provisions trade-off depending on the host used. When reared by chalk-browed mockingbirds, nestling cowbirds had higher food consumption, mass gain, and survival when alone in the nest than when sharing with 2 mockingbird young. In contrast, cowbirds reared in the nests of house wrens had higher food intake and growth when reared alongside 3 or 4 host young than when reared alone. (p. 7).

The results of their work suggest strongly that there is a trade-off at work here, and that the virulence of parasite offspring will be affected by the provisioning characteristics of the host environment.  Of course, they are quick to suggest that there are other factors potentially at work in differential growth rates, such as thermoregulation (larger broods can help each other thermoregulate) or size of the nestlings.  Nestling size is an interesting issue, because as the authors mention, cowbird young are larger than house wren nestmates but equal in size to or smaller than their mockingbird counterparts.  This may the competitive ability of the young either through physical competition between nestlings where size would be important, or because parents preferentially feed larger offspring.  (As a by-product, this also raises the longer-standing question of why host parents don’t do a better job at discriminating among their young for parasites in the first place;  for an explanation in terms of yet another trade-off, I’d refer you to this letter to Nature by Arnon Lotem as a possibility).

Wilson's Warbler feeding it's Cowbird chick  "offspring"

Why are you feeding this monster? (by Alan Vernon, on Flickr)

The work on trade-offs in this paper provide a simple and intuitive model for the action of brood parasites across a wide variety of situations, and then back it up with empirical data that demonstrate this trade-off in action.  It’s hard to ask for more from a paper!  Of course, as with every paper you’ll ever read, “more research is needed” (we have to say that, or we’re straight out of a job, aren’t we).  It wil be interesting to see if this trade-off does actually hold in other species, and combining the principles in this paper with a phylogenetic analysis would make for a fascinating approach. In the meantime, though, if you’ve read this far I’d urge you to take the lesson of this paper to hear and learn to look for the trade-offs inherent in many biological systems.  As a guiding principle of biology, I guarantee that you’ll see it almost everywhere you look.

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Group selection a done deal? Hint: no.

The modern theory of natural selection derives...

Image via Wikipedia

In reading Jerry Coyne’s review of David Sloan Wilson‘s new book, The Neighborhood Project, I came across this succinct summary of what I agree is the current feeling on group selection:

Group selection isn’t widely accepted by evolutionists for several reasons. First, it’s not an efficient way to select for traits, like altruistic behavior, that are supposed to be detrimental to the individual but good for the group. Groups divide to form other groups much less often than organisms reproduce to form other organisms, so group selection for altruism would be unlikely to override the tendency of each group to quickly lose its altruists through natural selection favoring cheaters. Further, we simply have little evidence that selection on groups has promoted the evolution of any trait. Finally, other, more plausible evolutionary forces, like direct selection on individuals for reciprocal support, could have made us prosocial.

These reasons explain why only a few biologists, like Wilson and E. O. Wilson (no relation), advocate group selection as the evolutionary source of cooperation. […]

At least, this agrees with my reading of the literature;  I’m hardly an expert in this area, but I’ve been swayed by the writings of people like Coyne and the pair of Stuart West and Andy Gardner (e.g. this paper, if you can get it;  this video is also well worth watching).  And nothing D.S. Wilson has ever written has convinced me otherwise.  Thus, I was especially surprised when I picked up a free copy of New Scientist from the Ultimo Big Night of Science – which, incidentally, was fantastic –  and saw that they had published an 8-page hatchet job (which is behind a paywall online here) by Wilson in which he claimed that group selection (a.k.a. multi-level selection or MLS) “is firmly re-established” in evolutionary biology.    “Today, though,” he writes, “there is near-universal agreement among those familiar with the subject that the wholesale rejection of group selection was mistaken and that the so-called alternatives are nothing of the sort” (p. viii).

One of the biggest problems with group selection is that it’s mathematically equivalent to other, better explanations of evolution like kin selection.  Wilson knows this:  he rather transparently tries to co-opt the criticism in the paper by stating it as though it works in reverse (“In addition, it has become clear that the supposed alternatives for the evolution of prosocial behaviour are actually equivalent to group selection”).  In what I consider a despicable move, he even quote mines Andy Gardner:  “‘Everyone agrees that group selection occurs,’ stated evolutionary biologist Andy Gardner in 2008.”  But it’s instructive to look at what Andy Gardner actually said, in this 2008 Nature summary of the ‘debate’:

 “Everyone agrees that group selection occurs,” says Andy Gardner of the University of Edinburgh, UK. Yet Gardner and his colleagues Stuart West and Ashleigh Griffin have trenchantly criticized David Sloan Wilson’s arguments on this subject — a critique to which David Sloan Wilson responded by initiating a lengthy debate in the community under the heading ‘If the theorists cannot agree…’.

Wilson leaves off the part where Gardner and his colleagues don’t agree with him at all, which is a favourite tactics of creationists.  I’ll leave the implication of that up to the readers.

So if everyone agrees that the two are mathematically the same, why not use group selection?  I’ll highlight the strong argument made by West, Griffin, and Gardner which you can read here.  In responding to Wilson’s critique of an article that the authors wrote, West et al. point out three things (p.376):

  1. “No group selection model has ever been constructed where the same result cannot be found with kin selection theory.”
  2. “The group selection approach has proved to be less useful than the kin selection approach.”
  3. “The application of group selection theory has led to much confusion and time wasting.”

If you’re interested in this issue, I urge you to read the linked PDF and follow up with some of the references they give.  I don’t know of clearer writers on this subject, and it’s a great place to start.

I disagree with a lot of what D. S. Wilson writes, but I respect his right to hold the opinions and his efforts to prove his position right.  That’s how science progresses, and if he can ever come up with some strong evidence for his position (which I don’t believe that he has yet), I’ll take a good hard look at it and make up my mind anew.  Until then, though, I would take him much more seriously if he would stop with the claims that everyone agrees with him when they obviously don’t.

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The Nowak controversy resurfaces…

Over at Boing Boing, Maggie Koerth-Baker takes up the issue of eusociality in insects that Martin Nowak and E.O. Wilson (and Tarnita, though she doesn’t get much attention when this issue is raised – I wonder if that makes her happy or sad?) raised such a hullabaloo over last year.  If you’re new to the issue or just enjoy good science writing, it’s well worth reading all the way through.  My own perspective?  I’m with most of the field in thinking that Nowak et al. were out to lunch on the evidence for kin selection, and as to whether group selection is in operation … well, let’s just say that I found this talk very convincing (h/t for that to Jerry Coyne).

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Gay zebra finches, oh my. Oh, wait…

Taeniopygia guttata (Zebra finch)

Image via Wikipedia

I’ve seen this paper about strong homosexual pair bonding in zebra finches pop up in a couple of places around the web, but it only really caught my eye when I read Carin Bondar’s somewhat breathless report on the matter entitled “The astounding strength of homosexual bonds in Zebra Finches: Ladies need not apply…”.  In essence, the researchers discovered that when you manipulate the sex ratio of zebra finch groups to be male-biased, male pair bonds form that display all of the same behaviours that female-male pair bonds do, and that when females are later reintroduced to these homosexual pair bonds, the male pair-bonds don’t break up.

It’s an interesting paper, and the findings are, well, pretty cool.  But I have to disagree – respectfully – with Dr. Bondar’s assessment of the startling nature of these results.  First, given that zebra finches tend to mate for life anyways, the finding that male-male pair bonds are strong shouldn’t come as a surprise if you think mechanistically.  In fact, I think it would have been a lot more surprising if the male-male bonds had been of a different quality;  if you think through the evolutionary implications, having a different mechanism for male-male as opposed to male-female bonds would imply that selective pressures on these types of bonds was different for some reason, and would really beg the question of why.  Instead of a single ‘mating’ mechanism (a combination of hormones and neurobiology among other things, which I’ll touch on again in a moment), this ‘conditional’ pair bonding would require either a single mechanism with an unintended consequence, or two separate mechanisms, one for male-male bonds and one for male-female.  That’s not out of the question, certainly;  many potential explanations for same-sex sexual behaviour in animals imply such mechanisms.  But to me, having a life long pair bond with females and then an entirely separate short-term pair bonding mechanism for male-male interactions would need explanation.  Indeed, as Dr. Bondar’s own blog post notes, “homosexual couples both COURTED and COPULATED with each other”;  even if homosexual pairings are adaptive (as they might well be!), it seems odd to waste even a little energy on copulation and suggests a single mechanism or set of mechanisms at work.

Second, it was already established that there are both hormonal and social / developmental mechanisms affecting same-sex preferences in zebra finches;  in particular, Elizabeth Adkins-Regan did a lot of work from the late 90s onwards on both of these mechanisms (and her student, James Goodson, has done a lot of great follow-up work on mapping the endocrinology and neurobiology of social behaviour in estrildid finches).  The finding in the article by Elie et al. that biased sex ratios promote homosexual pair bonds is interesting, but I wonder how different it is from the social deprivation work by Adkins-Regan and her collaborators.

Don’t get me wrong:  this is a cool article.  It deserved to be published, and it seems to make a couple of important contributions- exploring and quantifying the strength of these bonds was a worthwhile task, and the evidence it provides for the “social partner hypothesis” is worth looking at.  But the media has, as per usual, gotten most of the story wrong here (for instance, the BBC Nature story made it sound like the paper was the first to establish same-sex bonds in zebra finches – <sigh>), and while I share Dr. Bondar’s interest in the results, I don’t think that they’re nearly as shocking as she does.

As a postscript to this:  at the end of her article, Dr. Bondar says:

 However, long term studies will shed light on whether males will seek out females for the sole purpose of genetic propagation outside of their homosexual partnerships.  For the sake of their evolutionary future I hope they do :)

I’m not aware of anyone having tested this specifically.  But it’s been known for a long time that zebra finches engage in a fair amount of extra-pair copulating (i.e. they’re socially monogamous, but not sexually monogamous), so I would expect that the males are stepping out to enhance their reproductive fitness.

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Bees going, going, gone? Maybe so, but…

Honey Bee Colony Collapse Disorder, In Context – MYRMECOS.
Drove through a series of posts on colony collapse disorder today as linked to cell phones today following the hoopla over a report on the matter a couple of weeks ago and ended up at this awesome post with a truly eye-opening graphic.  It turns out that maybe the bees aren’t suddenly dying off like the news stories would have us believe.  It turns out that the western honey bee population has been declining since World War II!  Who knew?  It’s definitely worth reading, so have a click.

Oh, and cell phones?  Seems unlikely that they’re killing bees or giving us brain cancer.

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Odd happenings at Psychology today: did Kanazawa go too far?

I noticed – in my RSS feeds a day or two ago – an article entitled “Why are Black Women Less Physically Attractive Than Other Women”?  by Satoshi Kanazawa over at The Scientific Fundamentalist blog at Psychology Today.  Kanazawa is the guy behind the “why beautiful women have more daughters” idea that Andrew Gelman took apart on statistical grounds in that talk I linked to before, and he’s no stranger to provocative headlines in general.  Given the nature of the title and the often dubious nature of his evolutionary psychology claims, I left it unread in Google Reader to come back to.  However, when I clicked through today, I immediately got a 503 error, and a 404 (page not found) when I clicked through from Google, as in the screenshot.  The article is also nowhere to be found on the front page of the blog.  And so I wonder:  what happened?  It’s considered bad form to pull down articles with no explanation once they’ve gone up on the web, so barring some sort of easy-to-explain technical problem (somebody poured coffee on the server … that only publishes that page, since the rest of his blog is accessible?) I can only assume that Kanazawa or somebody higher up the chain pulled the plug.  There’s a good chance that no-one will notice this, but I’ll say it anyways:  this needs an explanation.  Wherefore art thou, oddball article?  I was so hoping to take a swipe at you…

Update: If you’d like to read the actual article, some enterprising soul has put it up on Scribd.  I’ll take a look at it later when I have a few minutes…

Update 2: PZ Myers at Pharyngula is unimpressed with the post.  I don’t think I need to add much here.

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My Ph.D. in plain English…

I guess that this meme has been going around on Twitter for a bit – I picked it up over at Carly Tetley’s blog Wildlife Research and Training – but I thought that since I had submitted my thesis to the department for review (avant de la défense), it was a good time to write about my Ph.D. work in plain English.

My Ph.D. research has been about the evolutionary foundations of social foraging behaviour in animals.  What does that mean?  Well, social foraging is the study of foraging decisions that animals make when they’re in groups, and when the decisions that they make depend on what the other members of the group are going to do.  This is an inherently game theoretical problem.  Now, that won’t mean much to you unless you know what game theory is, so here’s an illustrative example:  imagine that you’re at a party, and you get snackish.  You look over and see the snack table loaded with all sorts of goodies, from cookies to cakes and everything in between.  Individual (a.k.a. optimal) foraging research would study your decision of what snack to take based only on what snack you prefer.  Social foraging research would consider your decision-making process when you and your two best friends head to the snack table at the same time.  If all three of you like cookies, and there’s only two cookies left on the table, then it might be a smart decision for you to switch to cake – even though you prefer cookies over cake – rather than engaging in a bare-knuckle brawl over the last piece of chocolate chip heaven.  We can apply the same logic to the study of animals foraging and interacting in groups.  (If you’re paying attention, you might notice that there’s a third possibility where individuals forage in groups but make decisions independently;  this scenario corresponds to the outcome where everyone at the party has their own plate of goodies to choose from.  You forage together, but your decisions don’t affect each other).

Birds foraging socially...

A slide from my Ph.D. seminar: birds foraging socially.

We know that a lot of species across many taxa forage socially; for instance, it has been observed in birds, fish, mammals, and there’s even evidence for insects and possibly bacteria.  In these foraging species, the most common social foraging game observed is what’s known as the “Producer-Scrounger game”.  This is a game in which individuals take one of two roles, as the name suggests:  producers or scroungers.  Producers spend their time searching for food resources, while scroungers wait for a producer to find a food resource and then they join in the discovery.  Extending the party metaphor above, if you were producing you would be searching through the room to find a table with food on it;  a scrounger would be that lazy friend who waits for you to do the work of finding the goodies before strolling over to take advantage of your effort and help themselves to whatever’s on the table.   In foraging systems, there will be an mix of these two tactics where the “fitness” (usually measured by proxy as food intake, i.e. the number of cookies you scarf) of the two are equal.  This is what’s known as an ESS, or evolutionarily stable strategy.  I don’t want to delve too deeply into evolutionary game theory here, but you can think of the ESS as the best mix of producing and scrounging for you to play given the mix that everyone else is playing.

That’s the back-story to my Ph.D.  My research has focused on the theory of these social foraging games, and how to extend them to match real foraging situations more effectively.  For instance, most of the work done on the producer-scrounger game to date has been very agnostic when it comes to representing the world spatially.  This is deeply weird to me, because if you spend more than a few seconds looking at animals foraging in the wild it becomes obvious that spatial relationships – both between foragers and between foragers and their environment – have a significant impact.  Close foragers will interact more heavily; a patchy, broken landscape will be different to forage on than a regular grid with patches spaced evenly;  and so on.  Adding these spatial components into the theory of social foraging has been a major focus for me.

The other major theme of my thesis has been information use.  In behavioural ecology, “information” has a specific meaning that relates to how animals use observations of the world around them, especially other animals, to make decisions.  In foraging terms, this often works out to “Hey, how is Bob getting along at that patch over there?  Oh, he hit the jackpot!  Let’s go get some of that!”  Anthropomorphism aside, we can ask sensible questions about how animals collect and use public and private information.  Glossing over some nuances, we can think of private information as information gathered by the animals itself and not accessible to any other observer, like information about the richness of a patch gathered by sticking your head into it.  You can see what’s in there, but no-one else can.  Public information, on the other hand, is information that is accessible to anyone who’s paying attention.  If I’m a producer who has found a food table at a party, this becomes obvious to anyone tracking my movements when I begin stuffing cookies into my mouth as fast as I can.  Scroungers rely on public information to scrounge, otherwise the game would break down;  this means that information use is central to the study of social foraging.

For historical reasons, though, behavioural ecologists haven’t spent much time thinking about the mechanisms by which animals use this information.  They’ve vaguely assumed that natural selection will have worked this out, but haven’t done much to figure out what that product will be.  In social foraging, it has always been assumed that natural selection will bring animals to the producer-scrounger ESS (the optimal foraging strategy) on its own.  But we see animals adjusting their use of the producer and scrounger tactics over their lifetime, and often on a very short time scale (seconds, not generations) as they respond to rapidly changing environments. So how do they do this?  I’ve spent a fair bit of time looking at mechanisms that will allow an animal to learn an ESS, and how natural selection might act on those mechanisms instead of fixing an ESS right off the bat.

Answering these questions, both about space and learning, has required the use of computer simulations to augment the mathematical models that currently exist;  unfortunately, creating new formal models of these processes is an extremely difficult task and I prefer to let the computer do that work for me.  Therefore, I’ve spent a lot of time creating individual-based models and genetic algorithms to study these questions;  in the interest of keeping this post to a reasonable length, I’ll refer the interested reader to the Wikipedia pages for those topics, and I would be happy to answer any questions in the comments.

And I could talk about this for hours, but I think I’ll cut off the level of detail there so that I don’t drown innocent readers in progressive elaborations.  In any case, that’s a high-level view of the type of research that I have been involved in for the past four years.  Please feel free to ask questions in the comments!

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