# Mathematical Digest

### Short Summaries of Articles about Mathematics

in the Popular Press

"Evolution of Suicidal Signals," by Mike Speed and Graeme Ruxton. *Nature,* 28 March 2002, page 375.

From legions of thorny spines to bright colors indicating poison, animals'defense signals can be unmistakable. But the development of these signalsposes an evolutionary quandary: for a predator to learn that, for instance, abrightly colored species is poisonous, it would have to eat one. But rightafter the new species appears, it stands to reason their numbers would besmall, and this process of predator education would wipe them out. However,using a mathematical model of simultaneous evolution, biologist Thomas Sherratthas proposed a way out of the paradox.

*--- Rafe Jones*