Biologists have a problem that game theorists have already solved. The puzzle is called the competitive exclusion principle: in theory, when two species compete for the same resource, the better competitor eventually drives the other to extinction. This should mean that high-diversity ecosystems — like tropical rainforests with thousands of coexisting tree species filling similar ecological roles — shouldn't exist. They clearly do. The theoretical explanation turns out to involve Rock Paper Scissors.
The key is a concept called intransitive competition. In standard competition, if A beats B and B beats C, then A beats C. This leads to a single winner. But in Rock Paper Scissors, the relationships are circular: Rock beats Scissors, Scissors beats Paper, Paper beats Rock. No single player dominates. The cycle persists indefinitely.
Ecologists have documented this pattern in real systems. The best-known example is side-blotched lizards in California, where three male color morphs compete in a cycle: aggressive orange-throated males dominate blue-throated males, but blue-throated males outcompete yellow-throated males, and yellow-throated males do better than orange-throated ones because they adopt a sneaky mating strategy that orange throats can't counter effectively. Three types, circular dominance, stable coexistence.
The same dynamic appears in bacterial colonies. In a landmark experiment, three strains of E. coli competed in culture — each strain produced a toxin that killed one of the other two but was itself vulnerable to the third. Left to run in petri dishes with spatial structure (patches of bacteria rather than a stirred broth), all three strains persisted. Mixed together in a homogeneous environment, one strain won. The spatial dimension was necessary for the Rock Paper Scissors dynamic to maintain diversity.
The mathematical models extend the logic beyond three species. Researchers have shown that with enough trade-offs between competing traits, the intransitive logic can sustain much larger numbers of coexisting species. The catch is fragility: remove one species from the cycle and you can trigger cascading extinctions. In the game analogy, take Rock out of the deck and Scissors has nothing to lose to. In an ecosystem, a missing competitor can collapse the cycle that was keeping everything in balance.
The research doesn't mean nature is literally playing a tournament. But the competitive structure that makes Rock Paper Scissors work — circular dominance, no single winner, stable cycling — turns out to describe real ecological relationships well enough to predict which species can coexist and which ones can't. That's not a metaphor anymore. It's a model.