SANTA CRUZ, CA--An intricate three-way mating struggle first observed in a species of North American lizard has been discovered in a distant relative, the European common lizard. The two species are separated by 5,000 miles and 175 million years of evolution, yet they share behavioral and reproductive details right down to the gaudy colors of the males, according to new research published in the November issue of American Naturalist and now available online.
The triangle of competing strategies, which biologists liken to the children's game rock-paper-scissors, may be far more common than previously recognized--and may even shape the way humans behave, according to lead author Barry Sinervo, professor of ecology and evolutionary biology at the University of California, Santa Cruz.
"The models we propose in this paper are a general phenomenon for all animals, humans included," Sinervo said. When faced with the task of gathering food or finding mates, he said, "You either cooperate, or take by force, or take by deception. Those are the three ways you can make a living in any social system. It's one of those basic games that structures life."
Male European common lizards (Lacerta vivipara) adopt one of those three strategies when pursuing females. A quick look at their undersides reveals the strategy: males who sport orange bellies are brutes who invade other lizards' territories to mate with any female they can catch. But while they're gone, drab yellow-bellied males slink onto the vacant territory and mate with unguarded females. White-bellied males guard their mates closely, and cooperate with other white-bellied lizards to keep the yellows at bay. Hence the analogy to rock-paper-scissors: force (orange) defeats cooperation (white), cooperation defeats deception (yellow), and deception defeats force.
Predicted to exist by evolutionary theorists Sewall Wright in 1968 and John Maynard Smith in 1982, rock-paper-scissors games
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University of California - Santa Cruz