Male enhancement works!

I hate those commercials on cable TV for Enz*te, that fake “male enhancement” product that promises a “boost of confidence” for all the guys who take their little pill. I don’t believe it, of course—it’s probably a concoction of sawdust and rat droppings. But the phenomenon of male confidence as a function of the size of their physical attributes might just have some validity.

AL Basolo, who did some well-known work on mate preference in swordtails a few years ago (short answer: lady swordtails prefer males with longer swords), has a couple of new papers on the subject. She has looked at competition between males—the fishy equivalent of checking out the other guy’s equipment in the lockerroom—and found that the length of the sword makes a big difference in the struggle between males, even with no females involved.

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Xiphophorus helleri is a common aquarium fish with a distinctive feature: that long sword on its tail. The males have competitive interactions with each other that are fairly easy to assess: dominant males chase away inferiors, and inferiors avoid the winners, so you just have to record who is chasing who to sort out who thinks they are in charge. Usually, it’s the fish that is bigger overall that wins. The investigators suspected that the size of the sword might also be a deciding factor. Observations of pairs of fish matched for body size, but with natural differences in sword length, did not bear this out, however, showing little correlation. That suggests, as one might expect, that there are multiple factors that influence competitions.

To simplify those factors, they carried out what sounds to me like a very cruel experiment. Pairs of fish matched for body size were anesthetized, their swords chopped off, and replaced with transparent plastic swords of identical size. The difference, though, was that different length swords were painted on the transparent plastic—one lucky fish got a new painted sword roughly the same length as the old one, while the other got a sword half the length.

After recovering from their implant surgery, they were put together in a tank…and the truncated male consistently lost all competitions. I guess size matters, after all.

Without the gross surgical modifications, however, size wasn’t such a clear indicator of victory, so other factors must also play a role. A companion paper looked at stripes on the sword, and how they affected female interests. This work modified the tails digitally; a video recording of a hunky male was made, and then edited to either remove the stripes from its entire length, to remove them from the proximal half or the distal half, or left intact. The video was played back to a female, and the length of time she paid attention to it measured (longer is better).

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Female response to the four male video stimuli (pictured above each bar from left to right: complete sword, distal stripes, proximal stripes, no stripes). Bars with the same colour pattern did not differ significantly.

The lessons are clear. Having a long sword will help you intimidate and beat up your competition, and painting stripes along its length (or at least at the tip) will win you the admiration of females.

If you’re a fish, that is.

There is no necessary expectation that it will help at all if you’re a hairless ape, but if anyone tries it, let me know how it turns out.

Benson KE, Basolo AL (2006) Male–male competition and the sword in male swordtails, Xiphophorus helleri. Animal Behaviour 71(1):129-134.

Trainor BC, Basolo AL (2006) Location, location, location: stripe position effects on female sword preference. Animal Behaviour 71(1):135-140.

A rising starlet in evo-devo

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Nematostella, the starlet anemone, is a nifty new model system for evo-devo work that I’ve mentioned a few times before—in articles on “Bilateral symmetry in a sea anemone” and “A complex regulatory network in a diploblast”—and now I see that there is a website dedicated to the starlet anemone and a genomics database, StellaBase. It’s taking off!


Two legged goats and developmental variation

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Variation is common, and often lingers in places where it is unexpected. The drawing to the left is from West-Eberhard’s Developmental Plasticity and Evolution(amzn/b&n/abe/pwll), and illustrates six common variations in the branching pattern of the aortic arch in humans. These are differences that have no known significance to our lives, and aren’t even visible except in the hopefully rare situations in which a surgeon opens our chests.

This is the kind of phenomenon in which I’ve become increasingly interested. I work with a model system, the zebrafish, and supposedly one of the things we model systems people pursue is the ideal of a consistent organism, in which the variables are reduced to a minimum. Variation is noise that interferes with our perception of common underlying mechanisms. I’ve been thinking more and more that variation is actually a significant phenomenon that tells us something about where the real constraints in the system are. It is also, of course, the raw material for evolution.

Unfortunately, variation is also relatively difficult to study.



[Read more…]

I’m redundant-who needs a blogger?

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There’s a lovely article in this week’s Nature documenting a transitional stage in tetrapod evolution (you know, those forms the creationists like to say don’t exist), and a) Nature provides a publicly accessible review of the finding, and b) the primary author is already a weblogger! Perhaps there will come a day when I’m obsolete and willl just have to turn my hand to blogging about what I had for lunch.

For an extra super-duper dose of delicious comeuppance, though, take a look at this thread on the Panda’s Thumb. I wrote about Panderichthys, and a creationist (“Ghost of Paley”) comes along to mangle the phylogeny and make wild negative assertions about the validity of interpretations of fossils based on work from the Ahlberg lab…when Martin Brazeau of the Ahlberg lab and author of this new paper shows up to straighten him out.

And for my next trick, let me introduce you to Marshall McLuhan…

Brazeau MD, Ahlberg PE (2006) Tetrapod-like middle ear architecture in a Devonian fish. Nature 439:318-321.

Where are the spineless?

Hey! I’m supposed to host the Circus of the Spineless next week (I think on 29 January), and I’ve only received one submission so far! Someone must have written something somewhere about invertebrates, right? There is a set of rules for submissions, but it’s going to be simple: I’ll accept anything about any organisms outside the class Vertebrata.

I’ll spell it out. You can write about the phyla Acanthocephala, Acoelomorpha, Annelida, Arthropoda, Brachiopoda, Bryozoa, Chaetognatha, Cnidaria, Ctenophora, Cycliophora, Echinodermata, Echiura, Entoprocta, Gastrotricha, Gnathostomulida, Hemichordata, Kinorhyncha, Loricifera, Micrognathozoa, Mollusca, Myxozoa, Nematoda, Nematomorpha, Nemertea, Onychophora, Orthonectida, Phoronida, Placozoa, Platyhelminthes, Pogonophora, Porifera, Priapulida, Rhombozoa, Rotifera, Sipuncula, Symplasma, or Tardigrada, and that’s fine. You can even write about the Urochordata, the Cephalochordata, and the Myxini within the phylum Chordata. The overwhelming majority of animal species are fair game, so there is absolutely no excuse if anyone tries to send me a picture of their cat. Understand? Fish, frogs, lizards, birds, mammals, dinosaurs, and your baby pictures are right out.

I’m also going to accept multiple submissions, if you’ve been manic about documenting the breadth of biodiversity. We shall do our best to overcome the bias of the blogosphere for kitties and other furred and feathered and scaled beasties.

Although the tagline for the circus says it is a monthly celebration of “most anything else that wiggles”, I’m also going to break the shackles of metazoan chauvinism, so if you want to send in something about protists, lichens, fungi, plants, whatever, anything but things with a spinal column, I’ll accept them and put them in an honored category of their own.

Open Thread

Open Thread

I’m doing some traveling and touristy things with grrlscientist today, on top of somehow coping with the first week of classes (physiology and our freshman seminar in biological principles), and attending Drinking Liberally at the 331 Club tonight. I also have to get tickets to the Prairie Home Companion show that will be taped here at UMM on 11 February…it all adds up to me being a little scattered and distracted and otherwise occupied for much of today. You all are just going to have to fend for yourselves for a bit.

Here is a short list of things I should write about, but won’t get to today.

I do have some Science!!! to write about, but first I have to clear up some time in an overloaded schedule.

Deficiencies in modern evolutionary theory

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This is a post originally made on the old Pharyngula website; I’ll be reposting some of these now and then to bring them aboard the new site.

There are a number of reasons why the current theory of evolution should be regarded as incomplete. The central one is that while “nothing in biology makes sense except in the light of evolution”, some important disciplines within biology, development and physiology, have only been weakly integrated into the theory.

Raff (1996) in his book The Shape of Life(amzn/b&n/abe/pwll) gives some of the historical reasons for the divorce of evolution and development. One is that embryologists were badly burned in the late 19th century by Haeckel, who led them along the long and unproductive detour of the false biogenetic “law”. That was a negative reaction; there was also a positive stimulus, the incentive of Roux’s new Entwicklungsmechanik, a model of experimental study of development that focused exclusively on immediate and proximate causes and effects. Embryology had a Golden Age of experimentation that discouraged any speculation about ultimate causes that just happened to coincide with the time that the Neo-Darwinian Synthesis was being formulated. Another unfortunate instance of focusing at cross-purposes was that the Neo-Darwinian Synthesis was fueled by the incorporation of genetics into evolutionary biology…and at the time, developmental biologists had only the vaguest ideas about how the phenomena they were studying were connected to the genome. It was going to be another 50 years before developmental biology fully embraced genetics.

The evolutionary biologists dismissed the embryologists as irrelevant to the field; furthermore, one of the rare embryologists who tried to address evolutionary concerns, Richard Goldschmidt, was derided as little more than a crackpot. It’s an attitude that persists today. Of course, the problem is mutual: Raff mentions how often he sees talks in developmental genetics that end with a single slide to discuss evolutionary implications, which usually consist of nothing but a sequence comparison between a couple of species. Evolution is richer than that, just as development is much more complex and sophisticated than the irrelevant pigeonhole into which it is squeezed.

In her book, Developmental Plasticity and Evolution(amzn/b&n/abe/pwll), West-Eberhard (2003) titles her first chapter “Gaps and Inconsistencies in Modern Evolutionary Thought”. It summarizes the case she makes in the rest of her 700 page book in 20 pages; I’ll summarize her summary here, and do it even less justice.

She lists 6 general problems in evolutionary biology that could be corrected with a better assimilation of modern developmental biology.

  1. The problem of unimodal adaptation. You can see this in any textbook of population genetics: the effect of selection is to impose a gradual shift in the mode of a pattern of continuous variation. Stabilizing selection chops off both tails of the distribution, directional selection works against one or the other tail, and disruptive selection favors the extremes. This is a useful, productive simplification, but it ignores too much. Organisms are capable of changing their specializations either physiologically, in the form of different behaviors, morphologies, or functional states, developmentally in the form of changing life histories, or behaviorally. Evolution is too often a “theory of adults”, and rather unrealistically inflexible adults at that.
  2. Cohesiveness. There is a long-standing bias in the evolutionary view of development, that of development imposing constraints on the organism. We can see that in the early favor of ideas like canalization, and the later vision of the gene pool as being cohesive and coadapted, which limits the magnitude of change that can be permitted. It’s a view of development as an exclusively conservative force. This is not how modern developmental biologists view the process. The emerging picture is one of flexibility, plasticity, and modularity, where development is an innovative force. Change in developmental genes isn’t destructive—one of the properties of developmental systems is that they readily accommodate novelty.
  3. Proximate and ultimate causation. One of the radical secrets of Darwin’s success was the abstraction of the process away from a remote and unaccessible ultimate teleological cause and to a more approachable set of proximate causes. This has been a good strategy for science in general, and has long been one of the mantras of evolutionary biology. Organisms are selected in the here and now, and not for some advantage many generations down the line. Evolutionary biology seems to have a blind spot, though. The most proximate features that affect the fitness of an organism are a) behavioral, b) physiological, and c) developmental. These are the causes upon which selection can act, yet the focus in evolutionary biology has been on an abstraction at least once removed, genetics.
  4. Continuous vs. discrete change. This is an old problem, and one that had to be resolved in a somewhat unsatisfactory manner in order for Mendelian genetics (an inherently discrete process) to be incorporated into neo-Darwinian thought (where gradualism was all). Many traits can be dealt with effectively by quantitative genetics, and are expressed in a graded form within populations, and these are typically the subject of study by population geneticists. We often see studies of graded phenotypes where we blithely accept that these are driven by underlying sets of graded distributions of genes, such as the studies of Darwin’s finches by the Grants, yet those genes are unidentified. Conversely, the characters that taxonomists use to distinguish species are usually qualitatively distinct are at least abruptly discontinuous. There is a gap in our thinking about these things, a gap that really requires developmental biology. Wouldn’t it be useful to know the molecular mechanisms that regulate beak size in Darwin’s finches?
  5. Problematic metaphors. One painful thing for developmental biologists reading the literature of evolutionary biology is the way development is often reduced to a metaphor, and usually it is a metaphor that minimizes the role of development. West-Eberhard discusses the familiar model of the “epigenetic landscape” by Waddington, which portrays development as a set of grooves worn in a flat table, with the organism as a billiard ball rolling down the deepest series. This is a model that completely obliterates the dynamism inherent in development. Even worse, because it is the current metaphor that seems to have utterly conquered the imaginations of most molecular biologists, is the notion of the “genetic program”. Again, this cripples our view of development by removing the dynamic and replacing it with instructions that are fixed in the genome. This is bad developmental biology, and as we get a clearer picture of the actual contents of the genome, it is becoming obviously bad molecular biology as well.
  6. The genotype-phenotype problem. Listen to how evolutionary explanations are given: they are almost always expressed in the language of genes. Genes, however, are a distant secondary or tertiary cause of evolutionary solutions. Fitness is a collective product of success at different stages of development, of different physiological adaptations, and of extremely labile interactions with the environment. Additionally, a gene alone is rarely traceable as the source of an adaptive state; epigenetic interactions are paramount. We are rarely going to be able to find that a specific allele has a discrete adaptive value. It’s always going to be an allele in a particular genetic background in a particular environment with a particular pattern of expression at particular stages of the life history.

One unfortunate problem with discussing these issues in venues frequented by lay people is, you guessed it, creationism. Any criticism of a theory is seized upon as evidence that the theory is wrong, rather than as a sign of a healthy, growing theory. The Neo-Darwinian Synthesis is not wrong, but neither is it dogma. It was set up roughly 70 years ago with the knowledge that was available at the time, and it is not at all surprising that the explosion of new knowledge, especially in molecular biology, genetics, and developmental biology, means that there are radically different new ideas clamoring to be accommodated in the old framework. The theory is going to change. This isn’t cause for creationists to rejoice, though, because the way it is changing is to become stronger.

Textbook vs. Frontier

The Hwang Woo Suk stem cell research scandal has triggered quite a bit of concerned introspection in the scientific community. Orac has some useful comments on a good article in the NY Times that makes the distinction between “frontier science” and “textbook science”, where much of the current stem cell research is clearly on the frontier.

Much of science at the very frontiers turns out not to be correct. However, the way it is all too often reported in the press is that it is correct. We in science understand the difference between textbook science and the sort of frontier science that makes it into journals like Science. Indeed, we often lament that the very highest tier journals, such as Nature, Science, and Cell, tend to be too enamored of publishing what seems to be “sexy science,” exciting or counterintuitive results that really grab the attention of scientists–in other words “cutting edge” or frontier science. Such journals seem to pride themselves on publishing primarily such work, while more solid, less “sexy” results seem to end up in second-tier journals, which is why they are so widely read and cited.

I would add another factor, though: Hwang Woo Suk’s results were not at all unexpected, did not contradict any accepted scientific concepts, and were dramatic because they represented a methodological breakthrough. In a way, it was almost a “safe” category in which to cheat: lots of people are trying to transform adult cell nuclei into totipotent stem cells, it looks like a problem that’s just going to require a lot of trial-and-error hammering to resolve, and what Dr Hwang did was steal priority on a result he could anticipate would be “replicated” (or more accurately, done for the first time) in short order. This is one of the hardest categories of science to police, I would think. It’s frontier science all right, but it’s only one step beyond the textbook.

Orac’s comments about those sexy hot scientific results that get into the top-ranked journals also applies to weblogs. I’m guilty of the same thing: the articles I tend to summarize here are the ones that push at the edges of what we know, rather than the ones that consolidate what we already knew, which actually represent the majority of what I read. The solid stuff that is packed with gobs of detailed data on expression patterns of a single gene, for instance, is hard to make exciting to a general audience—when the conclusion of a long paper is that Hox1 represses transcription of Pax1/9 in the endoderm, it takes an awful lot of background exposition to try and make that interesting.

For the creationists out there, by the way, most of evolutionary biology is solidly in the “textbook science” category, which is one of the reasons biologists are so baffled about why the general public embraces criticisms of it.

Orsten fossils

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Bredocaris admirabilis

Ooooh, there’s a gorgeous gallery of Orsten fossils online. These are some very pretty SEMs of tiny Cambrian animals, preserved in a kind of rock called Orsten, or stinkstone (apparently, the high sulfur content of the rock makes it smell awful). What are Orsten fossils?

Orsten fossils in the strict sense are spectacular minute secondarily phosphatised (apatitic) fossils, among them many Crustacea of different evolutionary levels, but also other arthropods and nemathelminths. The largest fragments we have do not exceed two mm. Orsten-type fossils, on the other hand, have the great advantage in being three-dimensionally preserved with all surface structures in place and thus easier to interpret than any other fossil material. Orsten fossils are preserved virtually as if they were just critical-point dried extant organisms. Details observable range down to less than 1 µm, and include pores, sensilla and minute secondary bristles on filter setae and denticles. Orsten fossils also give an insight of meiofaunal benthic life at small scale, including preservation larval stages, and hence a life zone inhabited by the earliest metazoan elements of the food chain.

It’s a good browse over there. I think it’s useful to remember that the majority of the fauna of the world both extant and half a billion years ago is and was tiny and unfamiliar.