Posts Tagged ‘analogy’

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.


Friday, March 13th, 2009


















