Fritz Müller was an important early Darwinian and frequent correspondent with Darwin. Until now, nothing about Müller's life has been in the public domain, apart from a series of pamphlets by his cousin, Alfred Möller (1915-1921). To a linguistically challenged person such as myself, Möller's German volume was as good as no publication at all. David West has translated Möller's biography and included previously unpublished information into a readable yet carefully documented narrative.

Müller left Germany for Brazil because of his radical political and religious convictions. He was an atheist and advocate of "free love." In the face of the clampdown on freedom of academic thought and speech in Germany after 1848, most of us would have buckled under "the system," perjuring ourselves by swearing allegiance to church and state for the sake of a job.

Not Müller. He ditched the middle-class sweetheart whose parents would never have accepted his beliefs. He eschewed university positions in zoology and medicine to which he had formerly aspired, and lived for a while "in sin" with an uneducated laborer's daughter, Caroline Tollner. Müller married her only because his sister insisted that Caroline's life in Brazil would otherwise be ruined. The couple and their young children emigrated in 1852 to become subsistence farmers in Blumenau, a small German colony in southeastern Brazil.

Between clearing forest, building his homestead, farming (no chainsaws, just axe work), and defending against Indians, Müller somehow found time to keep up with science. In 1856, he left the farm, becoming a mathematics teacher in the high school in Desterro, on the coast. He had always preferred walking barefoot in the forest, so he found shoes irksome when confined to the city.

But freedom from agricultural labor gave him time to study the diversity of local animals and plants. He read Darwin's On the Origin of Species soon after it appeared. His major book "Für Darwin: Facts and Arguments for Darwin" (1869. London: J. Murray) was an extraordinary reductio ad absurdum of alternatives to Darwin, based on an early cladistic phylogeny of crustaceans. He discovered "Müllerian bodies," egg-like food provided by the petioles of Cecropia leaves (Moraceae) to the mutualistic Azteca ants that protect them, and did important research on marine invertebrates. Until his death, he spent most of his time (when not teaching or farming) as a field naturalist, gathering data on tropical biology.

Müller in 1866, with characteristic bare feet

Müller's greatest discovery is still, for me, Müllerian mimicry. In 1879, he used his flair for mathematics to show that one unpalatable, warningly colored species would benefit from resemblance to another unpalatable species by a factor equal to the square of the inverse ratio of the species' relative abundances.

With this nonintuitive result, based on simple algebraic assumptions about predator behavior, Müller must surely be the first mathematical evolutionary ecologist, as well as one of the most widely known, even to this day. His was also the first model of density-dependent selection (long before frequency-dependent and frequency-independent selection had been distinguished), and the first mathematical treatment of any mutualism.

David West should be congratulated for enabling a much richer understanding of this extraordinarily gifted naturalist than was previously possible. And what a pleasant surprise to learn just how unconventional and yet principled Müller was in everyday life!