Haldane and the Emergence of Modern Evolutionary Theory 553 HALDANE’S “MATHEMATICAL THEORY”A possible apocryphal story told by Haldane himself states that his interest in
genetics began at the age of 10 when, in 1901, his father, the physiologist, J.
S. Haldane, had taken him to hear A. D. Darbishire lecture on the then new
Mendelism. In any case, while still in school, Haldane noticed evidence of link-
age in Darbishire’s data on mice. He carried out breeding experiments with the
collaboration of his sister and a friend (A. D. Sprunt) but, due to the outbreak
of World War I, these results were only published in 1915. It was thus the first
discovery, though not the first published report, of linkage in mammals. During
part of the war Haldane was convalesced to New Delhi, where he read the reports
on Drosophila genetics from Morgan’s laboratory at Columbia University. Extend-
ing a method of Trow [1913; 1916], he devised the first explicit mapping function
to translate recombination frequencies to distances between loci on chromosomes
[Haldane, 1919].^12 In 1922, Haldane also published his rule of interspecific hybrids:
“When in theF 1 offspring of two different animal races [species] one sex is absent,
rare, or sterile, that sex is the heterozygous [heterogametic] sex” [1922, 101]. But,
in spite of his long-standing interest in genetics, until 1923, the mathematical
problems of natural selection had escaped his attention.
Why that changed so drastically during that year remains unclear. There is com-
pelling circumstantial evidence that part of the answer lies in religious objections
to evolution on the ground that natural selection is insufficient as a mechanism
to account for all of the past evolutionary changes. The early 1920s witnessed a
spirited public controversy between H. G. Wells and Hilaire Belloc over Darwin-
ism. Belloc’s religiosity — he hated Wells’ materialism — led to a rejection, not
of evolution, but of natural selection. Meanwhile, Bateson’s and other geneticists’
continued doubts about natural selection, as well as efforts to ban the teaching of
evolution in some US states, generated ample public controversy about the status
of that theory.^13 The prominent anatomist, Arthur Keith [1922a,b], stepped into
the dispute. In theRationalist AnnualKeith exhorted fellow “Darwinists” to pop-
ularize their views. The “very fact that Mr. Chesterton and Mr. Hilaire Belloc
could confidently assure readers of the Sunday Press that Darwin’s theory was
dead”, Keith [1922b] argued, “showed that those who are studying the evidence
of our origin, and who are Darwinists to a man, had lost touch with public intel-
ligence”. Five years later, Haldane rose to Keith’s call and also published a piece
in theRationalist Annualdefending and explaining Darwinism.^14 Eventually,The
Causes of Evolutionwould develop that argument in detail.
(^12) Wimsatt [1992] examines this work in its historical context, as well as its philosophical
underpinnings.
(^13) See Belloc [1920a,b], Bateson [1922], Huxley [1922], Keith [1922a], Livingstone [1922], and
Robinson [1922].
(^14) See Haldane [1927c]. This interpretation of the history was originally put forward by McOuat
and Winsor [1995]. The extent to which natural selection had fallen into disrepute was empha-
sized by Bowler [1989] who argues that the evolutionary synthesis should be regarded as a
Mendelian rather than Darwinian revolution.