Architect of evolutionary synthesis - Ernst Mayr - dies

The evolutionary biologist Ernst Mayr died on 3 February at the age of 100, after a short illness. A hugely prolific writer and researcher, he was instrumental in developing modern ideas in evolutionary theory.

It was Mayr who defined a species as a group of individuals that are capable of breeding with one another, but not with others outside the group. This led to the idea that new species can arise when an existing species becomes separated into two populations that gradually become too distinct to interbreed; it was an answer to a biological conundrum that had eluded Charles Darwin.

Walter Bock, a student of Mayr's in the 1950s and now an evolutionary biologist at Columbia University in New York, places Mayr's work on a par with two other great biologists, Theodosius Dobzhansky and George Gaylord Simpson. The three were, he says, architects of the 'evolutionary synthesis', the reconciliation of evolutionary theories with the processes of genetic inheritance.

Mayr's contribution was to define the species, which he did through his 25 books, including his first, Systematics and the Origin of Species, in 1942. "His books pointed out what was going on with the whole notion of the species concept," Bock says.