# Mathematical Digest

### Short Summaries of Articles about Mathematics

in the Popular Press

"How the Species Became," by Ian Stewart. *New Scientist,* 11 October 2003, pages 32-35.

This article describes a novel use of mathematics in understanding speciation, the process whereby new species emerge. Biologists recognize two kinds of speciation: The first arises when a group separates into two groups that are geographically separated; the second arises spontaneously without separation. The latter type, called sympatric speciation, was thought by biologists to be less common than the former, but since the mid-1990s that view has shifted. The article discusses how the mathematical notion of symmetry-breaking, which is used to describe many physical phenomena, could provide a basis for understanding sympatric speciation. Symmetry-breaking is the principle that describes, for example, why wind flying over a uniform desert of sand will cause parallel lines to appear in the sand. Speciation is far more complex, but basically the idea is that environmental stresses or other instabilities can cause the symmetry in a population to break, creating two groups with different species characteristics.

*--- Allyn Jackson*