Ernst Mayr

The controversial part is obviously a reference to Mayr’s theory of speciation. This is from Mark Ridley’s eloquent review of Coyne and Orr’s book on speciation in the TLS Dec 23, 04:

“Coyne and Orr divide research on speciation into three historical phases. The first began with Darwin in 1859. Then, from about the mid- 1930s, research moved on to a second phase. The influential figures were two immigrants to the United States, one from Germany (Ernst Mayr) and the other from Russia (Theodosius Dobzhansky). Mayr (who celebrated his 100th birthday this year), in particular, argued that new species arose when an ancestral species is fragmented into a number of geographically separate populations – for instance, when some colonists establish a separate population on an island at the edge of a species’ range. Now the separate populations will start to evolve in different ways, as they evolve adaptations to their different environments. If the food supply on the island differs from that on the mainland, an island population of, say, birds, might evolve different beaks or digestive machinery.

As the island and mainland populations evolve apart, they could eventually become so different that they are no longer able to interbreed. Speciation has then occurred. The crucial thing about the geographically separate populations is that they can easily evolve apart. Within one population, it is much more difficult to get two distinct forms to emerge. The constant interbreeding within the population tends to homogenize the forms, keeping them all much the same. But there is no interbreeding to stop the geographically separate populations from evolving apart. Since the 1940s, most biologists have accepted that new species can readily evolve from geographically separate populations of an ancestor.

The second phase tended to ignore genetics. In a way, this is odd, because it corresponded to, or just post-dated, the period when genetics was being incorporated into Darwin’s theory. (The science of genetics dates from about 1900. It turned out to provide a sound basis for Darwin’s theory – as was worked out in the 1910s and 20s.) There was research on the genetics of speciation during this phase, but the main research was biogeographic, looking at how the forms of a species vary in space. After all, if species arise from geographically separate populations, we expect to see signs of incipient speciation in those populations today: and that is the kind of prediction Mayr and his followers looked into.”

Mayr’s truly one of the greats.

My understanding of why Mayr has been a controversial figure is his adherence to the Biological Species Concept, which essentially holds that reproductive compatibility is the defining feature of a species. This concept, while generally quite applicable, breaks down when one considers natural hybridization in plants and animals. Certain bird species with separate ranges have zones of hybridization where their ranges meet. How then can these be defined as separate species if they freely hybridize (and produce viable offspring) under this definition. There is quite a diversity of species concepts (quite bewildering actually), but more accepted subsequent concepts call for unique traits to be incorporated in defining species.

Mayr was a great, however. 20 books and over 600 articles, and I believe something like 5-10 books in his 90s alone.