Thread by @QuantaMagazine

Rock-paper-scissors is a classic problem in game theory that’s also a touchstone concept in biology because of its relevance to evolution and ecology. ✊🤚✌️
Here’s why.
A thread: (1/9)

Since 1960, biologists have pondered “the paradox of the plankton”: How can ecosystems stably hold so many competing species? Why doesn’t the fittest eliminate the rest? (2/9)

One possible answer is the kill-the-winner hypothesis: As a predator thrives, it attracts more predators of itself. That response should in theory stabilize the system. (3/9)

But when modelers tested the original kill-the-winner idea rigorously, it failed — the ecosystem collapsed and all the species went extinct. (4/9)

quantamagazine.org/evolution-save…

So researchers modified the kill-the-winner theory to include the coevolution of predators and prey as their numbers changed. This change maintained species diversity much better. (5/9)

Rock-paper-scissors is another way to preserve species diversity. Some species compete intransitively — none is universally superior to the rest. Species can then coexist by cyclically trading off dominance over time or across space. (6/9)

Biologists continue to find naturally occurring examples of rock-paper-scissors scenarios that preserve biodiversity. Synthetic biologists have also taken advantage of this concept to build self-stabilizing systems of cells. (7/9)
quantamagazine.org/biodiversity-m…

In keeping with the idea that ecosystems can affect the dynamics of competition, researchers have observed that biodiversity itself can be a force in evolution. (8/9)
quantamagazine.org/biodiversity-a…

To learn more about how rock-paper-scissors and Nash equilibria affect systems of competition, read @MrHonner’s column on the subject. (9/9)
quantamagazine.org/the-game-theor…