The only problem was, the costs didn’t always exist. “If the handicap principle is true, people thought they should be able to observe the cost of signaling in the various signaling systems observed in nature,” said Michael Lachmann, a theoretical evolutionary biologist at the Max Planck Institute for Evolutionary Anthropology in Germany. “And that hasn't always panned out.”
Consider a baby bird that wants to grow as big and strong as possible. The chick should beg its parents for food whether it is hungry or not, unless the begging is costly. But careful experiments over the years have revealed that for most bird species, begging is cheap. “It’s easy to do and doesn’t attract predators,” Zollman said.
In Grafen’s signaling game, the low signal cost should lead to runaway begging among chicks, causing this mode of communication to lose meaning and disappear. For cheap signals to be stable, evolution must be playing a different game.
In a 1997 paper, the theoretical biologist Carl Bergstrom and his colleagues identified another conundrum: In order for honesty to be stable, the cost of the signal — even an honest one — has to be so steep that both signalers and receivers would be better off if the signal had never evolved. It is unclear to scientists how this situation might arise. “Simply identifying an evolutionarily stable strategy isn’t enough to tell you whether evolution can actually end up there,” said Bergstrom, of the University of Washington, who also co-authored the new study.
In the January issue of “Proceedings of the Royal Society B,” Zollman, Bergstrom, and Simon Huttegger of the University of California, Irvine, show that a partial-honesty model solves both problems. It is evolutionarily stable for both costly and cheap signals, with an equilibrium point that is reachable in a computer-simulated game.
For peacocks, partial honesty works like this: High-quality males will always grow long tails, but low-quality males will be polymorphic, with some growing long tails and some short. “So if you see a peacock with a long tail, it’s more likely he’s of high quality than low quality, but you’re not sure,” Zollman said. Meanwhile, peahens won’t fall for every long tail that sashays by. “If she sees the long tail, she sometimes chooses to mate with him and sometimes declines.”
Partial honesty works similarly when the signal comes cheap. Hungry chicks will always beg, and not-so-hungry chicks will sometimes beg too. “The parents should sometimes but not always feed a chick that’s begging, and should never feed a chick that isn’t begging,” Zollman said.
It’s a winning strategy in theory, but further research is needed to determine if real-world birds actually use it. Hugh Drummond, a biologist at National Autonomous University of Mexico who studies parent-chick interactions among blue-footed boobies, said parent boobies sometimes ignore intensely begging chicks for up to 20 minutes before suddenly coughing up a morsel, behavior that is seemingly consistent with the partial-honesty model. “But is the parents’ responsiveness capricious?” Drummond asked. “Or are they waiting for food to be sufficiently predigested to be ready for regurgitation?”
Biologists must unravel these subtle interpretations of animal behavior in order to answer larger questions about the evolution of honesty and deceit. "Although predictions of Zollman's model are superficially clearcut," Drummond said, "tests of them could get mired in ambiguities."
Reprinted with permission from Simons Science News, an editorially-independent division of SimonsFoundation.org whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the computational, physical and life sciences.
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Reply | Report Abuse | Link to thisIf the author would re-read if ever "The Selfish Gene" by Richard Dawkins in his seminal work or fast-forward to the 3rd Edition, he wouldn't need to bother proving all this deja vu all over again.
Reply | Report Abuse | Link to thisThank you for taking time to read the article. Could you please point me to the part of Dawkins' book that you have in mind?
Reply | Report Abuse | Link to thisChapter 9, Battle of the Sexes. Perhaps you got it going some finer way but it that distinction is without enough of a difference for my taste.De gustibus, non disputandum sit.... and over and out.
Reply | Report Abuse | Link to thisZollman et al. developed a model which suggests that often cheating or not giving honest information is a stable evolutionary state. However, their model, like all other formal models that have been offered for the handicap principle, considers only one signal. But birds and other organisms interact by multiple signals both in courtship and during aggressive interactions. If one of the signals becomes easy to fake to the extent that individuals of different quality can use it regardless of their real quality, or when a signal provides incorrect information, receivers that ignore it and prefer other signals to it can better decide about their options than individuals that include it in their decisions. In the case of peacocks, peahens demand not only a long, heavy tail but also defending an arena, raising the heavy tail and spreading it, and even rattling it. The peahen then chose the peacock that outperformed its rivals in all these tasks. By using multiple signals, it is easy to find out when a certain signal becomes easy to fake. I call the process by which signals lose their value by reducing their cost "inflation of signals," and provide examples from the real world of situations in which signals are ignored in the evolutionary process once they do not provide better information to receivers (Zahavi and Zahavi 1997, 2013). I suggest not sending field biologists to collect information to test a formal model when it is clear that the model does not represent the real world.
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