Mayr on speciation

2 minute read

OK, that headline looks like the title to a dissertation, which this isn't. But in honor of Mayr's recent death, I was looking through some of the things he has written about hominids, and I came across his book review of Jeffrey Schwartz's book, Sudden Origins. Reading this at once reminded me why Mayr has been such a giant in evolution that he spilled over into anthropology, and saddened me that there are so few representatives of such wisdom left.

Here are some quotes:

[Schwartz] correctly criticizes the strictly linear view of descent held by most anthropologists (p. 43), but by not thinking in terms of populations, Schwartz does not convert hominid history into a dynamic picture of the movement of geographically vicariant populations and subspecies. Such multidimensional thinking, introduced by the founders of the Evolutionary Synthesis, is not yet popular among physical anthropologists (978).
Phenotypic discontinuity does not conflict with Darwinian theory. If, for instance, a phyletic line evolves form the possession of two to the possession of three molars, the change does not occur by mutations giving one tenth, later one fifth, and one half of a new molar, but by one tenth, later one fifth, and then one half of the population having one new molar (978).

And here's rubbing it in:

What is the reason for Schwartz's failure in spite of his extensive reading and his efforts to make use of some of the most recent findings of molecular biology? Perhaps it is due to an insufficient consideration of some of the basic concepts of the synthetic theory. For instance, nowhere does he adequately emphasize that evolution takes place in populations and consists of the replacement of individuals, generation after generation. Furthermore, in numerous discussions of mutation in this volume, it is always implied that the gene (mutation) is the target of selection rather than the phenotype of the individual, and this favors acceptance of a theory of a saltational role of homeobox genes. Nor does Schwartz seem to appreciate that natural selection is a two-step process. Homeobox mutations occur during the first step, the production of variation. The fate of these mutations, after they have become components of new genotypes, however, is decided at the second step, the actual selection. Therefore, no conflict exists between the occurrence of homeobox mutations and the classical Darwinian process (979).

Consider that here, Mayr was in his early 90's. That some of us forget the lessons of the Synthesis is a discredit to us and our teachers, certainly not to the founders. Yet he patiently explains the way that today's developments in genetics should be incorporated into an evolutionary model, using the understanding that he helped the field to develop some sixty years before.


Mayr E. 1999. Sudden origins (book review). BioEssays 21(11):978-979. Wiley InterScience