Posts Tagged ‘dissertation research’

What’s sexier than sex and warfare? Taking the “arms race” one turn too far.

Wednesday, March 25th, 2009

Talk about sexy science. How could any science be any sexier than sexual selection?

Then combine sexual selection with “nature’s arms race,” and what do you get?  Science so titillating that even a seasoned science journalist might get a little…carried away.

This was the only explanation I could contrive yesterday morning after I read Nicholas Wade’s latest contribution to the New York Times Tuesday Science section. Only last week I posted about the importance of the arms race analogy to my dissertation research on the history of coevolutionary research. So I was very excited to see Wade’s piece, “Extravagant Results of Nature’s Arms Race,” gracing the cover of the Science Times.

Sexual selection is not really my bag—the evolutionary “arms races” that I write about are between hungry herbivores and unpalatable plants, not males of the same species. But the general concept is the same: offense and defense is heightened over many generations as a result of natural selection for the best-fed herbivore, or the least palatable plant, or, in the case of the sexual selection, the most successful (read: sexiest) male.

Sexual selection is a special case of natural selection where the most successful features do not always seem obviously adaptive. Take the classic example, the peacock’s plumage. Its lavishness makes no sense when you imagine the peacock trying to outrun a tiger. What can be more evolutionarily important than avoiding being eaten? Being sexy, of course. At some point in evolutionary history, females developed a preference for gaudy tails, and since the males with the gaudiest tails were the ones getting the action, more pretty boys in the next generation had gaudy tails. And so on– you get the picture.

This “female choice” type of sexual selection does involve an “arms race” of sorts: Peahens’ preference for gaudy tails escalates even as the gaudiness of male tails escalates—female preference and male success mutually reinforce and drive each other to greater extremes.

But invoking the “arms race” seems a lot more convincing when you are talking about out-and-out evolutionary combat. The second type of sexual selection, “male-male competition” is all about the escalating evolution of better and better weapons. In some species, males actually fight for sex, as with these male elephant seals battling for control of a harem of females. But in other species, it’s enough to look big and scary, to intimidate the other guy before he even tries to fight you. If your antlers are large, you might fight other males and win. But if your antlers are humongous?  You could be king of the lek without ever having to tangle. Possible bonus: Your “armament” may also serve as an “ornament” if females find your big antlers sexy. These University of Minnesota researchers found that lion’s manes did double duty, attracting females AND intimidating other males.

Wade’s Science Times article profiled a recent review paper on the diversification of male animal “weaponry” by Douglas Emlen at the University of Montana.

Dung beetles -- from a nice Discover Mag blog posting about the evolution of female dung beetle horns.


For your viewing pleasure, the piece focuses especially on the dramatically beautiful “horns” of dung beetles. And, as in most profiles of sexy science, Wade could not resist taking the next step, pushing toward that ultimate climax of sexy science.

What’s sexier than sex and warfare?

Sex and warfare and humans, of course:
“People have pathetically puny teeth and claws compared with the armaments of other dominant species. This is a sign not of pacific intent but of the fact that they manufacture their weapons.”

In other words, the “arms race” is more than just a metaphor that allows us to comprehend the evolution of elaborate organic weaponry on our own terms, those of technological weaponry. It’s an analogy between human and nonhuman evolved features.

If you read what I wrote about analogies last week, you’ll know that when evolutionary biologists posit such an analogy, they are claiming that evolved tusks and manufactured guns were generated in response to the same selective pressures. They have different evolutionary histories–in this case, the difference is even more extreme, since one has a biological evolutionary history and the other has a cultural evolutionary history.  But they are analogous because they share an adaptive function.

I am most fascinated by analogies like these, which effectively blur the boundary between biological evolution and cultural evolution. But it’s not just the boundary between biology and culture that becomes a bit blurry here. Wade interviewed a primatologist who claimed that it’s “very reasonable to assume that, as humans evolved and our culture became more complex, skills in tool making or other cultural behaviors took over from anatomical traits as ‘markers’ of a male’s competitive skill.”  In other words, the proposed mechanism for such a shift is also kind of hazy.  Claiming that cultural evolution just “took over” from biological evolution is not exactly a substitute for a testable hypothesis.

In any case, whether or not you think this is a reasonable assumption, you have to admit that it’s very compelling. Analogies are compelling—that’s why they are so useful.  They motivate us to make analytical leaps that, in the best of scientific circumstances, may also be empirically verified.

Sometimes those gravity-defying leaps also defy logic, however. Even a seasoned science journalist like Nicholas Wade may be seduced by sexy analogies into making such a logic-defying leap.

Wade analogizes between the organic “weaponry” featured in Dr. Emlen’s paper and a samurai helmet or a crossbow. So far, so good—these could make sense within the context of sexual selection.

Then, suddenly, Wade leaps into the geopolitical domain of the “menacing tanks and rockets that paraded through Red Square in Moscow in the days of the Soviet Union.” This is where the allure of the arms-race analogy becomes dangerous. Was the Cold War a result of sexual competition? Is the “the advent of chemical, biological and nuclear arsenals” really relevant to a piece on male-male competition?

The arms-race analogy has been scientifically productive, helping biologists imagine a series of evolutionary interactions that mimic the military escalation of the Cold War.  But when it leads us to relate sexual selection to global politics, it has probably overreached the limits of its utility. And when this overreaching happens on the cover of the Science Times, we must take pause.

Evocative analogies are powerful tools and—just like that nuclear arsenal—they should be used only with the greatest of caution.

Make an analogy between humans and cockroaches and then read this posting.

Friday, March 13th, 2009

At this moment in my dissertation work, I am transcribing my two-hour interview with ecologist Daniel H. Janzen.  In early December 2007 I flew to Philly and stayed there for one night, interviewing Janzen in his office at the University of Pennsylvania just 6 hours before I flew back to Toronto.  Clearly, I have waited far too long to transcribe the interview, which is typical of me.  I am always excited to rediscover what I learned during an interview.  Somehow I manage to forget almost everything we discussed in the minute after an interview ends—it’s as if my intense relief that it’s over triggers some sort of spontaneous amnesia.  So there are always many pleasant (and some excruciatingly embarrassing) surprises awaiting me.  But I find the process of the transcription totally grueling.  I really try to get every “um” and “ah” and grammatically disastrous sentence recorded for posterity, and this requires a lot of rewinding.  In the case of Janzen, who sprints from topic to topic in a rusty Minnesotan accent, rarely pausing for the insertion of a period or comma, my rate of transcription slows down considerably.  Not to mention that there are so many more words per minute in this interview.  I am 1 hour and 36 minutes into this interview and I have a 15-page transcript already.

There is a lot of good stuff here.  There’s an absolutely incredible story about botanist G. Ledyard Stebbins, who purportedly slept through Janzen’s thesis defense, but woke up just in time to compare the ants that Janzen studied to the chemical defenses that other plants produce, which protect them against attack by herbivorous insects.

At that moment, Stebbins gave Janzen what would become one of his most persuasive analogies.

My (point-and-shoot) pics of ant acacias from Santa Rosa National Park in Costa Rica (2006)

My (point-and-shoot) pics of ant acacias from Santa Rosa National Park in Costa Rica (2006)

Some background will help you understand this analogy.  Janzen’s dissertation research in Mexico exhaustively detailed the mutualistic relationship between “bull’s-horn” acacias and acacia ants.  As a graduate student in entomology at Berkeley, his first notion was just to study these ants—why were they so bizarrely fond of these prickly acacia trees?  It was by chance, or at least “serendipity,” that his attention shifted to the relationship between the ants and the acacia tree.  In his thesis, he concluded that there is a real mutual reliance between the two species.  The ants cannot live without the acacias: they take shelter and breed in the acacia’s oversized thorns and feed from the plant’s nectaries and Beltian bodies (little nutritive tabs that grow at the leaftips of the acacia).  Conversely, acacias that grow without a resident ant population rarely thrive. Without the ants to fight off other insects and the choking lianas that like to drape themselves across other plants, the acacia falls prey to both herbivory and competition with other plants.

Now, Janzen was not, by any means, the first to turn his attention to this surprising relationship.  Thomas Belt, a 19th-century British mining engineering who worked in Nicaragua for years, called the ants a “standing army” that defends the acacias against their enemies.   Harvard entomologist William Morton Wheeler challenged the claim that the ants were protecting the acacias, writing in the early 20th century that plants needed ants like a dog needs fleas.  Strong words, gentleman!  A raging academic debate that did not subside till Dan Janzen’s paper, “Coevolution of Mutualism Between Ants and Acacias in Central America,” published in the journal Evolution in 1966.

One of the things I’ve always loved about evolutionary biology is the evocative language that biologists use to describe processes and relationships.  Are the ants a “standing army” or a pack of voracious sap-sucking fleas?  Gives you two pretty distinct ecological pictures, right?

The study of coevolution between plants and insects has been built upon suggestive language like this.  This was a field that came into being during the Cold War, so who could really resist using the term “arms race” to describe the back-and-forth evolutionary responses between plants and insects?  Plants escalate their toxic biochemical defenses against hungry herbivorous insects, and insects escalate the tools they use to overcome those defenses.

So, what does it mean to claim that acacia ants function just like the chemical defenses used by other plants to fend off the insects that would eat them?  First, this analogy crosses categories: the ants, organisms in their own right, become (merely?) evolutionary adaptations of the acacias.  The ants are, Janzen would claim, an extension of the plant’s genome—in the same way that human technologies are extensions of our genome (which he also claims).  In essence, then, the ants become an adaptive technology.

But an analogy always operates in two directions.  The reciprocal effect is to grant the chemicals produced by plants a new identity.  The best analogies (just like the best metaphors) associate entities that seem, otherwise, completely dissimilar.  In this case, the analogy between ants and plant chemicals breaks a long-accepted boundary between what animals can do and what plants can do—or, rather, what plants can’t do, passive pieces of green furniture that they are.

I mean, when we talk about animals, we use active verbs.  We see them causing things to happen, acting—in short—with agency, if not intentionality.  Plants, on the other hand, when they’re not simply invisible, don’t tend to act.  They don’t move, they have no sensory organs.  Even when we see them, we don’t think of them as agents.   Even when a plant has an effect on its environment, it appears somehow passive, and the effect is often considered a by-product of some other more planty function.

Coevolutionary analogies, by contrast, make plants and animals equal partners.  More accurately, they’re adversaries. And plants, so long seen as the wallpaper of the world, suddenly become embattled veterans of an ancient chemical war with animals.

This kind of transmission of meaning and agency between plants and animals has real effects on science (this is one of the themes of my dissertation).  It’s one reason that I became so interested in Janzen.  The man analogizes like it’s going out of style.

More importantly, he is very careful to distinguish between “analogy” and “metaphor.”  Janzen does not speak in metaphors, because metaphors make comparisons that could not be literally true.  If he makes a comparison between, say, armyworms gobbling up an entire field of corn and Germany invading Poland, he does not mean this comparison metaphorically.  To him, hungry caterpillars and power-hungry humans are the same thing. The entities interacting are unimportant: locusts or leopards, hummingbirds or humans, it doesn’t matter—only the interactions themselves are important.

Janzen describes this as a fundamentally ecological perspective on the world, but I see it as a fundamentally evolutionary perspective, instead. In evolutionary biology, limbs or organs are analogous when they perform the same biologically adaptive function but have different evolutionary origins.  When Janzen draws an analogy between human warfare and plant-insect warfare, this is also what he means: same adaptive function, different evolutionary origin.

Ants or wild parsnips, humans or cockroaches—we might organize them into different categories, but evolutionarily, they are all subject to the same forces.  It’s part of what gives evolutionary biology its explanatory power.  And also, let’s face it, what makes it so darn fascinating.

This is one good-looking cockroach, right?  Also from Santa Rosa National Park.

This is one good-looking cockroach, right? Also from Santa Rosa National Park.

On really striking out and (sometimes) striking el oro

Tuesday, February 24th, 2009

About luck. The notion has been irritating me for the past few days. I’ve always been interested in how chance operates in my own life. Like most people, I usually construct a nice satisfying retrospective narrative about my life. But chance has always played an unsettling starring role, throwing a wrench in the aesthetics of that erstwhile smooth story arc—you know, the one where I make wise conscious decisions and directly control the events of my own existence?

My sense of the importance of chance has only been heightened in my dissertation research, in observing its importance in the lives of pretty prominent scientists. This is not just the historian’s impartial eye, observing how life deals different hands to different players. This is the witness borne by those players themselves! Renowned biologists—known for their brilliance and not, typically, for their humility—have repeatedly credited chance with the paths of their careers. Paul Ehrlich. Dan Janzen. These guys have taken unusual and sometimes unpopular stances on ecological issues—in other words, they give the impression of deliberately charting their own courses. And yet, Janzen loves the words “serendipity” and “serendipitous,” and applies them liberally to the story of his own career.

Of course, when Janzen speaks of “serendipitously” stumbling upon an ant acacia while roving across Costa Rica in the early 1960s, he is not talking about pure chance. He is talking about the convergence of luck and preparation; the effect of a particular experience upon a mind primed with just the right kind of knowledge and previous experiences. The true luck is almost always in the timing of that critical experience.

Like Janzen, we’ve been doing some roving across the Costa Rican landscape, hoping for such a lucky convergence. We have no concrete information directing our mushroom search at the moment; only a knowledge of the general rainfall patterns for the season and a sense of where oak trees might be found.

Walking along a forest trail during the dry season might remind you of autumn in North America. Deciduous trees lose their leaves here just as they do in the temperate zone—it just happens to be during the “summer,” the drier and sunnier time of year. According to the Costa Rican bird Bible, Skutch and Stiles’  Birds of Costa Rica, it was the Spanish that declared the dry season summer, arriving with their memories of a hot and dry verano and cool and wet invierno.

If you’re lucky enough to have made it to an oak-dominated forest, however, you might still look up and see a truly regal canopy above your head. These oaks are closely related to the evergreen live oaks of the Southern U.S. And while “regal” might seem a cliché, under the circumstances, it’s spot-on. The oaks we have seen here are hundreds of years old, many feet in diameter, and verdantly populated with mosses, lichens, and bromeliads. There’s something so vital about the silhouette of an oak tree. The leaves burst so densely from the awkward joints of its branches. Its body looks haphazardly assembled and, at the same time, absolutely coherent. Coherence is a concept, but I would even say that an oak tree is cohesive, in a purely physical sense, as if it is gathering its deep green pigmentation along with moisture and light and a body of cool air, directly from the air around it. When each branch supports a dozen bromeliads, and their bright fuchsia and maroon and yellow-green leaves glowing translucently from above, this sense of pure organic gravity, of substance and sustenance, is intensified.

Rhapsodies over the beauty of oak trees, however, do not a successful collecting trip make! Oak trees are also mycorrhizal symbionts, living in intimate collusion with fungi, whose hair-like mycelia connect with their roots underground, sharing nutrients and minerals in an exchange that sustains both tree and fungus. Finding an oak means finding its fungal symbionts, which, if we’re lucky, have fruited above ground, producing those reproductive organs that my dear husband so desperately seeks: mushrooms.

This is where serendipity comes in. There are thousands of acres of forest reserve and national park in Costa Rica. Most of this is completely inaccessible, or else only moderately accessible, especially for people that need to collect mushrooms, photograph them immaculately, in situ and against a gray background with an herbarium collection number, take DNA samples (because this is, after all, part of a DNA barcoding project), and then dry them completely in a food dehydrator. So, via various points of entry, public, private, and otherwise (meaning, we’re not quite sure who owns the land or the road by which we reach it), we try to get at this inaccessible core of forest.

For our purposes then, these roads and trails are essentially random cuts in the forest. We can steer ourselves toward higher altitudes, where oaks and other mycorrhizal tree species are more common, or toward the rainiest provinces, but the decisions made decades ago to build a trail along this ridgeline or blast a switchback for the road into that hillside, may or may not take us precisely where the mushrooms just happen to be fruiting today. As much we have prepared for this trip, there will always be the discomfiting suspicion that somewhere—maybe even just a measly kilometer to the east or the south—the mother lode of mushrooms is elbowing its way up through soil and detritus, where we will never find it.

Anyway, that’s how it feels today. Fieldwork, especially when the task is opportunistic collecting in an attempt to document fungal diversity in the region, can sometimes boil down completely to luck. And luck is not with us in other ways, as well. We are three days into this collecting trip and have yet to see the collection and export permits for the mushrooms we are supposed to be collecting. Bryn started the process of applying for these permits more than two months ago, at the moment he knew that his teaching trip would be extended into a collecting trip. Unfortunately however, the term “process” implies that there is a straightforward method for obtaining such permisos. In reality, successfully scoring a permit turns mostly upon finding a reliable contact on the ground, a contact who also has a functional working relationship with the relevant bureaucratic body. It’s not entirely clear what went wrong, but it seems to be a little bit of a failure in both aspects (maybe more heavily the former than the later, I might add).

In any case, we have not yet been able to collect in Parque Nacional Tapantí-Macizo de la Muerte, as we do not have the relevant permits. So, we are reduced to making even more random forays into the landscape, in hopes of finding mushrooms on land where park rangers are not likely to be breathing down our necks. This morning, over weak coffee (Costa Rica is a coffee-producing nation that reserves its most drinkable beans for export and tends to disappoint the palate with weak and bitter brews in person.), Bryn identified a small “protection zone” called Cuenca Rio Tuis, perhaps a couple of hours drive from our hotel in the small village of Orosi. It seemed a little far away, but also unlikely to be heavily monitored, and according to our topographical map, it reaches a peak elevation of 1963 meters and may even have oaks.

It was a lovely drive, on a fantastically sunny day, over mountainside roads that rapidly drop and fall while they and around Lake Cachí. Everywhere that we drove, a brief wave or a “Buenas!” out the window of our car transformed that standard hard-edged impersonal glance you turn toward a strange car into smiles—people are incredibly nice to strange gringos blowing unexpectedly through their tiny little hamlets.

coffee plantation

At first, at the higher elevations, we drove through coffee plantations. Coffee is Costa Rica’s grano de oro, “grain of gold,” which brought prosperity to this nation named “rich coast.” Workers alongside the road were spraying the beans with a pesticide. These workers are, reportedly, mostly Nicaraguans, since Costa Ricans are no longer willing to lower themselves to earning something like $1/bushel for picking el grano de oro. The shade-grown varieties actually appear to receive a good deal of sunlight, especially since many of the scattered trees planted to give them shade are deciduous, with only bare branches remaining, which cast crooked shadows (if not actual shade) over the coffee. Other plots are stocked with imported eucalyptus, trees that at least retain their leaves during the dry season.

dscn0249Halfway through the drive we made delicious tomate, aguacate, y queso fresco sandwiches for ourselves at the roadside. At lower elevations we began to see the sugarcane fields, where men with machetes hacked away at their stalks. Near the end of the day we passed a plant where trucks full of sugarcane stalks pulled in for processing. The men trailed down the roads slowly in the wake of the trucks, looking exhausted, machetes still in hand, while a smoggy burnt-caramel smoke filled the Orosi valley.sugarcane truck

Finally we reached our little forest reserve. Or…..we’re pretty sure that we did. After all, most of the roads are not signed and the GPS is often little help in finding our position on what seems to be a pretty imperfect map (it’s missing an entire huge lake?!). Driving into the reserve on the potholed dirt road through increasingly tiny villages (where people seemed even friendlier, in inverse proportion to the size of their towns), we started to get excited about the wooded hills that we could see ahead. When a road winds around so much, you really just have to keep faith that eventually you will reach that mirage of forest on the horizon.

abandoned houseWe passed a couple of abandoned house, one with half-collapsed porticoes and arches and windows that still contained shards of glass. We’ve tried to decipher graffiti from the side of the building, but it’s hard to read from my passing photograph: Aqui es solamente / No se aqui que / porque aqui.” Bryn says I’m wasting my time trying to read this nonsense, like a bathroom wall in the basement of some bar in Toronto. It’s something like: “Here is only / I don’t know here what / why here.” Indeed.

Anyway, eventually, we had to turn on the 4-wheel drive to cross a little river with steep embankments on either side and a little catarata (waterfall) in the center. But we never got much higher, and we never got much closer to that elusive deep core of forest. We drove as far as we could on the road, to a place where the mud was ridged so deeply in a sharp turn that we couldn’t imagine the car handling both challenges simultaneously. So we did a little bit on foot. And it was disappointing mycologically.

But for me, with the mud on my boots, and the humidity that layered my face in sweat the moment I started to climb the steep trail along the hillside, and my first glimpse of something as common as a bird-of-paradise flower—all of these started to melt that icy nucleus of Torontonian slush and snow at my center. Running my hand along a mossy boulder, I had a tempting moment of synesthesia, and I was certain that I could taste the deep green in the blade of a bromeliad just above my head. So, although we struck out mycological today, I feel finally that I have really arrived in Costa Rica, and I’m excited to try our luck again tomorrow.sunset drive back to Orosi