Sad news today of the death (at age 100) of Ernst Mayr. His must-read What Evolution Is will always have a vital place in my library. It’s one of the major classics of biology–or science writing in general.

As an ornithologist, Mayr classified many birds, most notably risking the hostile terrain of New Guinea to catalogue the region’s birds of paradise. But he will arguably be best remembered for formulating the concept of species that students still use today.

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.


We may never again see someone so influential, in this era of large research groups and even larger databases, [Walter] Bock [Columbia University evolutionary biologist] adds. “Things have changed,” he says. “You can’t look at single people any more.”