EVOLUTION

Not a Flock of Dodos

The Latest Chicken Research Flies in the Face of Creationism

Why did the chicken cross the road … and start clucking out a series of raucous alarm calls?

That is the question that scientists in Australia recently asked—and nicely answered—in a study that offers new and elegant support for the inexplicably maligned theory of evolution.

More than 40 percent of polled Americans agree with the statement: “Humans and other living things have existed in their present form since the beginning of time.”

The research, described in the September issue of the journal Animal Behaviour, is the latest in a seemingly endless stream of nails, screws, and spikes that scientists have driven into the coffin of creationism—albeit with shockingly little impact on Christian fundamentalists, many of whom remain committed to undermining evolution’s teachings in public schools. More generally, the research deserves celebration as a quintessential example of why the scientific method is the way to understand the world around us.

The findings are worth highlighting because the battle over evolution is still far from won in this country, despite the overwhelming mass of scientific evidence that supports this model of how the biological universe works. School districts are still having fights over how to address evolution in curricula. And astonishingly, more than 40 percent of polled Americans agree with the statement: “Humans and other living things have existed in their present form since the beginning of time,” while less than half agree that “humans and other living things have evolved over time.”

Which gets us to the chickens.

Chickens have long been popular subjects for studies of “sexual selection,” an aspect of evolutionary theory first proposed by Charles Darwin himself. The more widely taught evolutionary principles of “natural selection” and “survival of the fittest” speak to the importance of an individual’s ability to weather life’s challenges, occasionally with the help of new, advantageous mutations. Sexual selection refers to a particular component of that formula for success: Convincing a member of the opposite sex to mate with you, so you can have more offspring than your less-fit competitors before you die. And as anyone who has visited a bar knows full well, generally it’s the males that need to do the convincing.

Toward that end, the males of many species are heavily ornamented. The theory of sexual selection says that such visual extravagances can serve as a signal of an individual’s health. It takes energy, after all, to maintain colorful tufts of hair, brilliant waddles, or other seemingly goofy goo-gahs. Indeed, in many instances these accoutrements are barely manageable—think about the peacock’s tail—and are the first to go shabby when a male gets sick or is parasitized. Over generations, as females repeatedly choose the most flamboyant males as a surrogate means of picking the healthiest sperm on the block, these exotic traits become more prevalent.

Experiments have generally confirmed that females are suckers for male décor. When female ornamental chickens (Gallus gallus) are given a choice between two males, presented to them in separate cages simultaneously, they go for the one with the most brilliant orange feathers and the reddest, fleshiest comb. The new experiments sought to go further: Do a mate-choice experiment in a more natural setting, in which males could not just show off their colors but literally strut their stuff—that is, behave in ways that might contribute to their attractiveness.

Here is where the Australian research team helped resolve a longstanding quandary in evolutionary biology. Chickens, it has long been known, are among a number of species in which individuals—generally males—will let out warning calls of various sorts when a predator is near. These calls are extremely valuable to the group as a whole. When, for example, a male chicken lets out the call that means “aerial predator approaching!” other chickens in the vicinity crouch low and look upwards, as though watching for a hawk. When a male gives the signal indicating an approaching land-based predator, the others stand erect and look toward the horizon, as though searching for a fox.

But what’s in it for the one doing the signaling? Under the strict rules of natural selection, an animal ought to do whatever it can to boost its own odds of survival—like hiding as soon as trouble appears and leaving others to fend for themselves. Running around making a lot of noise (okay, not necessarily crossing the road while at it) is surely not the best way to avoid being noticed by a predator. It just didn’t sit well in evolutionary theory, though possible explanations have been proffered.

Beyond the specifics of evolution itself, the new research on poultry paramours is also worth highlighting because it is such a fine example of the simple power of the scientific method.

Some scientists have suggested that even if the signaling individual sacrifices himself, he may at least end up saving some close relatives, a perhaps reasonable, though imperfect, substitute for saving his own DNA for posterity. Others have suggested that the chaos that often ensues after raising a predator alarm may confuse the would-be attacker and help protect the whole group.

But for chickens, at least, the real advantage did not become clear until David R. Wilson, Christopher S. Evans and their colleagues at Macquarie University in Sydney did their unprecedented mate-choice experiments, which involved small groups of male and female chickens in natural, open spaces—places where females could base their choices not just on the degree of decoration among a few caged males but on the actual behavior of those males.

To their surprise, the team members found that in naturalistic conditions, feather brightness and comb color were not the best predictors of which male a female would swoon for. Outside of caged conditions, behavior, it turned out, was more important than sartorial style. And specifically, “the best predictor of mating and reproductive success was the rate at which males produced anti-predator alarm calls.”

No one knows, of course, what is running through those little female bird brains. Perhaps the gals are attracted to the selfless heroism of those who shout warnings. Or perhaps, as Animal Behaviour’s editor Daniel T. Blumstein opined in an accompanying commentary, female chickens “are attracted to honestly scared males.”

These are, after all, chickens.

Whatever is going on, the males willing to squawk when danger looms are the ones who get the girls. And the math suggests that even if, now and then, this bold behavior does prove fatal, the overall odds are that, by then, those pluckily clucking pieces of prey will have sired more offspring than their quieter cousins. And thus, gratifyingly, another puzzle piece that seemed not to fit into Darwin’s theory—a behavior that had been presumed to decrease a male chicken’s chances of evolutionary enlightenment but which, in fact, now appears to increases those odds—clicks into place after all, like so many before it. Darwin’s rules keep proving true.

The fact that nearly half of Americans refuse to acknowledge this could be tolerated if these very same people were not tirelessly foisting their beliefs upon others—and not just upon their own children, who are arguably victims of child abuse for being taught such a warped picture of reality, but upon school districts across the country. Once again, for example, the Kansas board of education is poised for an electoral war over the teaching of evolution in that state’s classrooms. The Louisiana legislature also recently passed the Louisiana Science Education Act, which calls upon the state’s Board of Elementary and Secondary Education to “create and foster” a school environment that promotes “objective discussion of scientific theories being studied, including, but not limited to, evolution, the origins of life,” and a other indisputable elements of the scientific canon.

Beyond the specifics of evolution itself, the new research on poultry paramours is also worth highlighting because it is such a fine example of the simple power of the scientific method. There was a presumption: a male chicken that clucks when a predator is present is essentially a dead duck, one that female chicks would hardly consider dating. And there was a hypothesis: Maybe there is more to clucking than meets the eye. There was an experiment: Let’s see how these blustering boys really do. Then there was a result, and a revamping of scientists’ thinking—a revamping that if anything only bolsters the overarching framework of evolutionary theory.

So here’s to the scientists who, while school boards and others wave the flag for creationism and “Intelligent Design,” just keep on following their beaks, and sticking to the facts. Perhaps someday a majority of Americans will believe the evidence these researchers have repeatedly confirmed. Perhaps someday we, like the proverbial road-crossing chickens, will get to the other side.

Rick Weiss is a Senior Fellow at the Center for American Progress and Science Progress.

Tags: evolution

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