Haldane and the Emergence of Modern Evolutionary Theory 81of the Chetverikov school, of Dobzhansky, and of Mayr himself were important
contributions to evolutionary biology. But, the question that Mayr never an-
swered is why this work should not be regarded as, another naturalist, Sheppard,
had regarded it in 1954, as providing experimental data testing the models of by
mathematical population genetics.
What has so far been said recovers a central role for mathematical population
genetics in the history of evolutionary theory. It remains to discuss Haldane’s place
in it relative to Fisher and Wright. But this will require some philosophical choices
about the nature and role of theories. If it is accepted that global (“unifying”)
theories constitute the benchmark for what constitutes good theorizing, then it
is arguable that Haldane was not as important as Wright and Fisher or, later,
Kimura. But there are at least two reasons to question such a benchmark in
general, and especially in the context of evolutionary theory:
(i) much of that theoretical enterprise consists of the construction of models to
explore and test different proposed mechanisms of change: different models
of hereditary transmission of genes (polyploidy, haplodiploidy, so on), rela-
tions between genes and traits, population structures, and modes of selec-
tion at different intensities. Here grand theory recedes into the background.
What replaces them is,first, the strategy of model construction articulated
first — and with full clarity — by Haldane in 1924 at the beginning of the
“Mathematical Theory”; andsecond, to a surprising extent, many of the
mechanisms that he first modeled (certation, kin selection,etc). Theoretical
population genetics in practice proceeds largely by Haldane’s methods, so
much so, that his role in their origin has disappeared in a remote history
that everyone has internalized to such an extent that any explicit mention is
occasion for surprise. (The last point is similar to what Haldane [1953] said
in his response to Waddington);(ii) while universal theories may have many appeals, it is an independent ques-
tion whether they are correct. No one knows whether the alternatives pro-
posed by Fisher, Kimura, or Wright are correct in the sense that evolutionary
history on Earth is best accounted for by any of their single preponderant
mechanisms. Haldane did not think so and it may well turn out that this was
a wise choice, that evolution has proceeded by a plurality of mechanisms,
different ones in different ecological and genetical contexts, and the idea of
a univocal theory is a chimera best cast aside as an inspired dream of a dif-
ferent and more heroic age. At the beginning of the twenty-first century, as
modes and models of selection proliferate, it appears that Haldane, rather
than Fisher or Wright wasmethodologicallywise.In 1990, Princeton University Press reissuedThe Causes of Evolutionwith
annotations and a long “afterword” by E. G. Leigh.Causes, Leigh [1990] argued,
“was eclipsed somewhat by the work of Fisher and Wright, apparently because
Haldane refused to found a system” (p. xxii). Nevertheless, this was exactly