Two Geneticists: J.B.S. Haldane and C.D. Darlington 

By Gavan Tredoux

Originally published in PINC, April 2000. Some typos are fixed here.

J.B.S. Haldane (1892-1964) and C.D. Darlington (1903-1981) belong to the great school of British geneticists and biological statisticians produced by a country basking in the afterglow of the eminent Victorians, Sir Francis Galton and his cousin Charles Darwin.   Darwin, of course, introduced evolution and banished superstition, but it was the more versatile Galton who elevated the studying of human traits to the level of science; inventing modern statistics, psychometrics and behavioural genetics in the process.  

Galton's long intellectual coattails started with his protégé and biographer, Karl Pearson, who followed Galton's lead in developing the mathematical statistics required to perform what came to be known as biometry - the measurement of biological phenomena, including the rigorous study of evolution.  Where Galton invented the 'regression' and 'correlation' statistics,  and 'percentiles of the normal distribution', Pearson generalized these concepts to provide an unprecedented level of mathematical sophistication and technical capability, most notably in goodness of fit to statistical models, and skew distributions.  Pearson's rival Sir Ronald Fisher formulated the analysis of variance; but he too was following Galton's lead,  since attention to statistical variance was totally absent before Galton insisted on it.  Joining Pearson and Fisher were Julian Huxley, J.B.S. Haldane and C.D. Darlington: between them, this eminent group not only cured the concrete foundations of the modern science of evolutionary biology, they also built the first dozen floors.  What is more, they were all eugenicists; commencing with Pearson, who become an especially zealous convert to Galton's dominating passion.

Galton himself had coined the word 'eugenics' in 1883, and had used his considerable prestige in the last decade of his life to publicly promote its cause.  Few realize now that this was always an unpopular cause, so much so that Galton kept relatively quiet about it for the first 30 years after he had first raised it in his pivotal Hereditary Genius (1869). Things had turned round by 1939, largely due to the work of Galton's disciples, when the Hermann Muller's "Geneticist's Manifesto" was signed by the leading scientists of the day, including Fisher, Haldane, Huxley, and Lancelot Hogben. This near-consensus of leading scientific opinion was destroyed by WWII and the aftermath of Nazi atrocities. 

The eminent geneticists and Galtonians, J.B.S. Haldane and C.D. Darlington, have now slipped from popular memory. First Haldane volunteered himself into obscurity by self-imposed Indian exile, then Darlington was drowned out by the Sixties cacophony and its after-din.  This despite both being highly successful, best-selling authors of popular science in their day.  Both still repay careful attention: Haldane for his tragic descent into Stalinist orthodoxy and irrelevance, Darlington for his genetically-based universal history - which is still unique, challenging and richly suggestive.

J.B.S. Haldane was the son of an distinguished scientist in his own right, J.S. Haldane.  An outstanding student at school, and rigorously trained at home by his father, he had original work on genetics accepted for publication while still a schoolboy.  Going up to Cambridge, he surprised everyone by changing his field of study after a year, from science to classics; exactly why we still don't know for sure. Nonetheless he took first class and went on to become an outstanding scientist anyway.  Haldane could do this because he possessed a rare combination of literary and scientific ability, becoming one of the most outstanding authors of science writing for broader audience - a field now known as popular science.  There are many writers of popular science, but few are first-rate scientists in their own right; Haldane was one, Richard Dawkins is another.

The field Haldane devoted his career to was genetics, more specifically the mathematical theory of evolutionary genetics, which he helped to construct from the elements put in place by Galton, Pearson, and Mendel.  His career moved from Cambridge, to the John Innes Agricultural Institute, to University College London, and eventually exile in India; not because he liked to travel, but because he inevitably quarreled with any and every institution he encountered. Stubborn and prickly, with a near-Serbian capacity for bearing grudges, and hard to get along with, he either made enemies or acolytes. Yet his career might easily have been stillborn altogether when he interrupted his Cambridge education to enlist in the Great War of 1914-8.

Haldane stands alone as the one veteran of the Great War to publicly admit that he thoroughly enjoyed the conflict. Robert Graves sullenly suffered in the trenches, and then bitterly wrote Goodbye to All That.  Siegfried Sassoon wrote poignant poems. Haldane conducted unsanctioned night-raids in no-man's land and mortared the Hun for kicks. He devised new bombs and thoroughly enjoyed the scientific aspects of poison gas and gas-masks. After the war, he would write a very interesting pamphlet on the merits of chemical warfare, pointing out (unanswerably) that fatalities and injuries due to poison gas were modest compared to bullets, bayonets and bombs; and his claim that governments supported the suppression of poison gas because they preferred prolonged and bloody conflicts to shorter and more clinical ones is still worth considering. 

Haldane had an unusually robust constitution, perhaps due to his Scottish ancestry, and a rock-solid grip of his sanity.  When he became interested in physiology, he experimented on himself and anyone who would care to volunteer with him.  He injected himself with substances and calmly noted their harmful effect.  He exposed himself to gases in closed chambers and calmly observed his deterioration under the influence of the gases.  Eventually this affected his health permanently, but not until he had scores of self-experiments under his belt.

Haldane was always left-leaning, a tendency that became exaggerated with age. Between the wars it was still possible to be a scientist, a socialist, a meritocrat and a eugenicist.  The left believed then in the value of science, and hoped that the Soviet union would lead the way in solving social problems through application of science and reason, replacing what they considered irrational superstition and prejudice.  For the left, science was a liberator. This is why Cyril Burt, the great psychometrician, was really a progressive and a social reformer, destroying the irrational elements of the class system by enabling elevation on the basis of objectively determined merit - which is what the new IQ tests did. Likewise,  Karl Pearson considered himself a socialist, and pointedly refused a knighthood.  Of course, the enthusiasm of the left for the Soviet union was misplaced; some saw this immediately and broke ties, like Bertrand Russell, but others became fellow-travelers or worse.

Aside from his work on mathematical biology, Haldane quickly established a reputation as an outstanding writer of popular science, turning out a steady stream of magazine and newspaper articles, interspersed with best-selling books.  This allowed him to live more comfortably than an academic might, and to acquire a degree of fame that few of his colleagues or rivals could match. Though he was gruff and difficult, he was generous with his relatively comfortable means, and often subsidized his students from his own pocket when he was unable to obtain grants for them.  This happened more than once, since Haldane was not suited to, and could not be bothered to play, the academic grant game.

Together with Haldane's growing popular reputation came a gradual descent into open politics, which sharply accelerated in the 1930s, by the end of which he had become a full-blown Marxist.  Nevertheless, Haldane was a biological realist, however strained the relationship between those views and his growing socialism, then Marxism, became. Marxism might obscure those views, but it never completely subsumed them. The most accessible guide to his biological realism, and his recognition of hereditary individual differences, can be found in his collection of popular essays, The Inequality of Man. First published in 1932, this predated his descent into ideological Marxism.  Here we find him remarking that:

The progress of biology in the next century will lead to a recognition of the innate inequality of man. ... In a scientifically ordered society innate human differences would be accepted as a natural phenomenon like the weather, predictable to a considerable extent, but very difficult to control.

Like many of his left-wing contemporaries, Haldane also endorsed a version of eugenics. Indeed, Haldane was a thoroughgoing Galtonian in all important aspects: not merely because he worked for many years in the division of  University College, London, that Galton had established and endowed; but because he had absorbed the Galtonian spirit that infused and sustained his field :

The only clear task of eugenics is to prevent the inevitably inefficient one per cent. of the population from being born, and to encourage the breeding of persons of exceptional ability where that ability is known to be hereditary.

Haldane was much impressed by a pioneering study of twins carried out by the German,  Johannes Lange. Lange had discovered that criminality is heritable, by showing that the criminality of a twin significantly increased the likelihood that the other twin would be a criminal.  Haldane energetically promoted Lange, writing a foreword for the English edition of Lange's engaging Crime as Destiny: A Study of Criminal Twins (German edition 1929, English edition 1931). His then-wife, Charlotte Haldane, did the English translation.  In his foreword, Haldane referred to Lange's study as a "masterpiece" of "scientific psychology". So he was well aware of the inheritance of behaviour traits. Anticipating Richard Herrnstein's syllogism by 40 years, he was also aware that heritability rises with equality of opportunity:

Universal education leads, not to equality, but to inequality based on real differences of talent.  Where there is equality of opportunity there is no excuse for failure. The self-made American man who realizes this fact, commonly appears ruthless to the European aristocrat, who, just because he knows that he does not owe his position to innate ability, is often more considerate of his inferiors.

But Haldane knew full well that these ideas were not going to be well received by the Marxists, and was able to state this clearly when his socialism had not yet developed into a full-blown case of Marxism:

The test of the devotion of the Union of Socialist Soviet Republics to science will, I think, come when the accumulation of the results of human genetics, demonstrating what I believe to be the facts of innate human inequality, becomes important.  I am a very strong believer in innate human inequality, but I would like to point out that there is another source of innate inequality, namely, segregation ... So a belief in innate inequality does not mean a belief in the omnipotence of heredity. But this belief is certainly incompatible with the sentimental and unscientific views often associated with Socialism.

Haldane resolved this obstacle for his own socialist (then pre-Marxist) beliefs by imagining a socialist that embraced human inequality.  It was never clear exactly what this kind of socialism would entail, because Haldane's politics inclined to the sentimental and not the systematic, so we have no exposition from him on the subject; just vaguely stated hopes of the following kind: 

It seems to me ... that while the conclusions to be drawn from a study of human inequality are not necessarily favourable to capitalism, they are, at any rate, favourable to some forms of socialism, though perhaps not to all forms.
[The Inequality of Man, 1932]

 As it was, his socialism became hard-core Marxism.  He was drawn into organized labour circles in the 1930s and eventually became a card-holding member of the Communist Party. He relished being photographed with striking labourites, and churned out 345 articles for the Daily Worker.  His attachment to the Soviets had become a distinct liability by the onset of WWII. The military valued his scientific advice, not to mention his generous habit of subjecting himself, and those foolish enough to accept his dare, to the effects of atmospheric poisoning while testing the prolonged confinement in submarines; but by now the military had to consider Haldane a security risk.  His liberal scorn for the opinions of the military could not completely disguise his steady alienation from society. This was a very English society of public intellectuals, ensconced safely in the freedom of academic institutions; their eccentricities tolerated and even admired. But Haldane's socialist eccentricity developed into a form of subjection, to the discipline of a party organization controlled and funded by an external power. Whereas the college eccentric is very much a part of his surrounding society, Haldane was progressively part of an external party and not of his own society. How did this square with his bloody-minded independence? It was the triumph of sheer stubbornness over good sense. 

The Lysenko affair provides a striking illustration of Haldane's damaging intransigence. The story of Stalin's glorified peasant farmer, Trofim Lysenko, and his stranglehold over Soviet science, has been definitively recorded by the Russian geneticist Valery Soyfer, in his recently republished samizdat: Lysenko and the Tragedy of Soviet Science (1994) .  Lysenko was a Lamarckian who relentlessly pushed a cockamamie account of agricultural genetics that amounted to the inheritance of acquired characteristics, well-larded with boundless contempt for those who would study flies rather than honest-to-goodness wheat.  This idea resonated with the creation of the "new Soviet man" by the sheer act of Stalinist will, so Mendelian genetics was exiled, its practitioners banished and murdered, and the biological sciences within the Soviet union were set back decades.  It is less well-known that the Lysenko farce played to smaller audiences in the West, among the intellectuals and scientists who had flocked to the communist left, like Haldane, before and during the war.  

Some turned away from Lysenko and the Soviets in disgust, notably Hermann Muller; others leapt to Lysenko's defense. One either defended Lysenko or left the party. Darlington and other mainstream Western geneticists were instrumental in exposing Lysenko's folly, especially in the pages of the journal Heredity (which Darlington had co-founded with R. A. Fisher).  But  Haldane came to Lysenko's defense, according him every benefit of the doubt; using his still considerable public prestige when appearing on radio debates, where he would argue Lysenko's case against none other than Darlington and Ronald Fisher, among others.  Eventually, this fiction became impossible for anyone to bear, and Haldane's intransigence could no longer restrain his intelligence. But rather than speak out against the destruction of Soviet biological science, he chose a sullen silence instead, and withdrew from active party activities.  Up to his death, Haldane remained loyal to Stalin, even years after the revelations by Khrushchev! 

 If  Haldane noticed that his friend, the great Soviet geneticist Nikolai Vavilov, had died in the "Saratov" Soviet labour camp in 1943, he didn't dwell much on it in public. Vavilov had trained in Britain with William Bateson, and had pioneered the study of plant genetics. It was Vavilov who had suggested that the history of humans could be traced through the genetic history of domesticated agricultural plants, the spread of the plant varieties giving a good idea of human migration. Vavilov had invited Haldane to visit the Soviet Union in 1928 and had befriended him. They corresponded for many years, and Haldane mentioned Vavilov frequently in his science popularizations.  But Vavilov had become the leader of (classical) Soviet genetics by the early 1930s, and this earned him the  undying enmity of Lysenko.  Arrested and tortured by Stalin's henchmen, he was relentlessly interrogated in sessions of the following kind:

Interrogator Khvat: Who are you?
Vavilov: I am academician Vavilov.
Interrogator Khvat: You're a bag of shit, not an academician.
[Soyfer, 1994: 145]

Vavilov eventually broke down and confessed to various crimes against the Soviet Union, including the cultivation of corn, implicating a galaxy of agriculture experts in the usual manner. He was sentenced to death but languished on death row until he died of the effects of malnutrition and ill-treatment, shortly after his sentence was commuted to 20 years of hard labour.   

By the early 1950s, Haldane had run out of British institutions to quarrel with. He used the Suez crisis to announce that he was emigrating to India, to join the Indian Statistical Institute, in high dudgeon over "Western imperialism".  The Vietnam war would later show that academic conceit really does know no bounds, when the eminent French mathematician Serge Lange visited Hanoi in the belief that his presence would deter US bombing.  Haldane cultivated precisely this sort of conceit, but not entirely honestly. In fact, he had been planning to emigrate some time before the Suez flap.  He was nearing retirement anyway, and was attracted to India because he had served there for a while in the First World War, training soldiers in the use of bombs, and had liked it.  Inevitably, his tenure in Indian academic institutions would proceed from enthusiastic beginnings to bitter endings. Despite all this, he continued to produce the stream of superb scientific work that distinguished his career, just as he had moved from squabble to squabble in England without diminishing his intellectual reputation. 

Haldane was diagnosed with rectal cancer in the early 1960s, and bore the news with characteristic fortitude and a wickedly grim sense of humour. He composed a poem called "Cancer's a Funny Thing", which commenced:

I wish I had the voice of Homer
To sing of rectal carcinoma,
Which kills a lot more chaps, in fact,
Than were bumped off when Troy was sacked.
I noticed I was passing blood
(Only a few drops, not a flood).
So pausing on my homeward way
From Tallahassee to Bombay
I asked a doctor, now my friend,
To peer into my hinder end,
To prove or to disprove the rumour
That I had a malignant tumour.

The longer-term effect of exile was obscurity.  By the time of his death in 1964, Haldane was no longer of figure of much public importance in the West, even if he was revered in India. Today Haldane is barely remembered in either India or England. His unswerving loyalty to Stalin is a great pity, since he deserves far better than the notice that we are forced to give him today: J.B.S. Haldane, the eminent geneticist, war hero and fellow-traveler to the end.

Cyril Darlington lived in much the same world as Haldane, but was entirely unlike him in temperament and politics. Where Haldane leaned, and then lurched, to the left; Darlington tended to the right.  His conservatism may have owed something to his own progress from unremarkable middle-class beginnings to the very peak of genetic science between the wars.  Younger than Haldane, he was schoolboy during the Great War.  At age 20, he entered the John Innes Agricultural Institute in 1923, as an unpaid voluntary worker, eventually becoming its director in 1939. The Innes institute was the center of British genetics at the time, and was home to another of Karl Pearson's bitter rivals, William Bateson. (Bateson had rejected one of Pearson's papers submitted to the Royal Society, which forced Pearson to found the journal Biometrika, assisted by Galton's backing, financially and intellectually; and Bateson had also trained Haldane's friend Nikolai Vavilov). Haldane himself had coveted the directorship that Darlington assumed, but he had been denied it by his reputation for being difficult and a poor administrator.   

Darlington  pioneered the study of chromosomes, through the study of plant genetics. Elected to the Royal Society in 1941, he moved to Oxford in 1953, becoming the Keeper of the Botanic Gardens and Sherardian Professor of Biology. He remained at the University until his retirement in 1971, and Oxford itself until his death in 1981. Like Haldane, he also reached a wide audience with popular expositions of genetic fundamentals, and published a prodigious bestseller;  first issued as The Facts of Life in 1953, this eventually became Genetics and Man and went through many editions ( like Haldane's popular science, it was published by the Pelican imprint of Penguin, in an inexpensive mass-market paperback).  He would also publish widely in fields that might be considered on the periphery of genetics: linguistics, scientific education, psychology and philosophy.

Variation in human abilities (a more accurate notion than 'human inequality') was as obvious to Darlington as it was to Haldane, and he completed his career with a remarkable universal history from the standpoint of a geneticist, The Evolution of Man and Society (1969).  Universal history was then as much in decline and disrepute as it is now; but Darlington succeeded marvelously. There are few aspects of human history that he did not touch on,  from human prehistory, through the foundations of agriculture, the ancient and classical civilizations, and the rise of Europe to the present day.  He also found time to explain why it was that early Christianity embraced monasticism and nunneries (lack of fertility due to overly aggressive outbreeding),  why the Jews collected taxes for Mediaeval Europe, and how it is that the genetic Irish propensity for story-telling made its way into Norse mythology (through the Irish settlement of Iceland).

The key to this history is the influence of genetic capability, as channeled and regulated by human breeding systems. Darlington's interest in the broader ramifications of genetic variation can be traced back, in print at least, to the early stages of WWII. An article in Nature in 1943,  "Race, Class and Mating in the Evolution of Man", Darlington laid the foundations for his massive universal history:

"The group effect of inbreeding is that it gives homogeneity, predictability of offspring from parent, adaptation, easy transmission of culture, sometimes too easy, and hence potential stability of culture, It is a conservative agent and it conserves itself best in the most conservative peasant communities. It opposes initiative. It reduces conflict, sometimes disastrously. If applied to specialized classes it conserves their differences and increases their fitness. In India the endogamous caste system has preserved a store of variation which, if released by free crossing or recombination, might well enable us to reconstruct the whole genetic range of mankind.

On the other hand, inbreeding, while increasing temporary fitness, reduces flexibility. It reduces the means of acquiring fitness to new conditions. ... Homogeneity provides the optimum condition for epidemic. Heterogeneity permits selective survival and recovery. This advantage of heterogeneity merely shows in a special way how inbreeding frustrates the long-term function of sexual reproduction, the recombination of genetic differences, recombination which cannot take effect without the combination of these differences by outbreeding.

The long-term function of outbreeding has moreover come to imply a short-term advantage. Species become adapted to outbreeding and the adaptation ... cannot be overridden without risk. ... [T]here is a conflict between the advantages and the disadvantages of out breeding at both genotypic and phenotypic levels and as between the short view and the long one. 

How then is this conflict to be resolved ? In general the combination of inbreeding and outbreeding in parallel rather than in sequence gives the greatest efficiency in the utilization and selection of the available variation of mankind and, consequently. the most rapid evolution. A subdivision of mankind into races and classes is, therefore, highly advantageous provided that we can assure its instability. This seems to be no insuperable difficulty at present. The rapidity of differential population changes, the increase of mobility, the changes of methods of production, and the technical requirements of government, have upset the stability of races and classes as well as the adaptation which partly justified that stability."
[Nature, no 3855; September 18, 1943; p 318]

Darlington was a race-realist, and an unusual proponent of the virtues of both inbreeding (race formation) and outbreeding (race submersion), depending on the historical context.  He was also a thoroughgoing sociobiologist, well before both William Hamilton and Edward O Wilson had made the subject famous.  He took the influence of genes on all aspects of human society and history for granted, proceeding to work out a sweeping account of human history that properly concentrated on details and  implications.  This is much more productive and interesting than yet another rehash of a pseudo-debate that had already been settled conclusively by Galton in the previous century. 

In his history, Darlington is especially aware of the distinctive contributions of certain populations (races) to their societies, and of their genetic adaptation to economic and cultural activities peculiar to them. Thus, Cornish tin miners, who were probably from Anatolia originally, were successful miners all over the world; not because of a fortuitous culture, but because they were genetically adapted to mining - that is, to those traits which tend to make better miners.  Similarly, the ancient Beaker culture was spread throughout Europe, not by imitation, but by the migration of the Beaker people themselves.

Inbreeding, coupled with long-term selection, produces groups with special abilities; historically, many societies have existed in more or less stable form as highly successful collections of specialized inbreeding groups laminated together by a caste system. At time, these societies have expelled some of their constituent racial castes. Spain expelled the Jews in the late 15th century; their catastrophic loss was Holland's priceless gain.  Likewise, the French expelled the Huguenots in the 17th century, only to lose a highly skilled and accomplished population to Britain, South Africa and other regions.  It is a central theme of Darlington's history that this loss was not simply a loss of acquired skills, it was a loss of genetic capability, and a permanent one at that.  This is a genuinely profound rethink of traditional history, which has always dealt in the acquisition of knowledge by culture alone, through education and imitation.  But notice that Galton too was well aware of the same phenomenon and had frequently drawn attention to the example of the Huguenot migration, and the distinctive contributions of natural ability that they had made to English society; typically, he had anticipated everyone else by over half a century:

Whatever other countries may or may not have lost, ours has certainly gained on more than one occasion by the infusion of the breed of selected sub-races, especially that of Protestant refugees from religious persecution on the Continent.   It seems reasonable to look upon the Huguenots as men who, on the whole, had inborn qualities of the most distinctive kind from the majority of their countrymen ... . Consequently England has been largely indebted to the natural refinement and to the solid worth of the Huguenot breed, as well as to the culture and technical knowledge that the Huguenots brought with them.
[Hereditary Genius, p xxii, Prefatory Chapter to the 1892 edition]

It need hardly be said that Darlington's view of history fell rapidly into disfavour as the radicalization of the 1960s took effect.  His acceptance of racial differences in intelligence did not endear him to the new breed of academics or the professional intellectuals of the magazine and 'new media' circuit.  If Hume's Treatise 'fell still-born from the press', Darlington's crowning achievement, The Evolution of Man and Society,  all but withered away in infancy. But do not judge a work by its current critical reputation.

Darlington's final work, The Little Universe of Man, was published in 1978.  Together with Genetics and Man and The Evolution of Man and Society, this completed his trilogy on Man.  Darlington acknowledged his debt to Haldane:

I may also add that, although I parted company with him over communism, it was in the long youthful discussions with the late J. B. S. Haldane, twenty years earlier, that my three books on Man had their roots.
[The Little Universe of Man, p. 17]

The theme of this final work is what Darlington called the 'created environment', and individual human differences.  Behaviour geneticists have recently realized that genes seek out conducive environments, but Darlington had long anticipated this. Not only do genes seek out favourable environments, among humans they create them too. This complicates any separation of the effects of heredity from environment, since, in practice, human heredity must completely dominate the environment.  Darlington was well aware that he was on dangerous ground here.  He identifies three taboos surrounding the study of man:

The European taboo on the discussion of man as an animal lasted until it was eventually broken by Darwin and Huxley. But in our dynamic world its place on the forbidden list was already being taken by another taboo, that on the discussion of sexual behaviour and this lasted, as we can still remember, more than another fifty years. In due course in the 1930s there followed a third taboo which now dominates the study of human problems and is likely to continue until another generation rejects and ridicules its parents' prejudices. This third line of defence against the understanding of man is the taboo on the study of hereditary differences. The one belief or emotion that unites the jarring nations today appears to be the need not to notice, and certainly not to discuss, the existence of differences between them in terms of their permanent underlying causes. Innate hereditary or genetic differences must not be admitted between individuals or groups, between classes or races, or even between the sexes. But above all what must not be discussed, what must be rejected, are differences in the foundations of human behaviour, the study of brains, of instincts, and of intelligence. These foundations are complex and happily concealed from the public view. They must remain concealed. In a world already overcrowded and over-troubled they might cause more trouble. 

Concealment, of course, means deception, pretence, and confusion. Successively with evolution, sex, and human differences, it has meant that scientists are pushed into deceiving, first themselves, then their pupils, and then the public. Thus fear of the truth, on the part of the public or of the establishment, which used to protect the central mystery of religion, has now shifted to fields of inquiry which are, next to religion, the most difficult. For in heredity and intelligence we have two subjects which inherently we can never entirely understand. Established opinion is objecting only to our making a start. 

The heredity of man is contained in a sperm having atoms in number of the order of 10^12. The cells in his brain are of a lower order of multiplication (about 10^10). In their totality, in the sense that every cell is qualitatively useful, these numbers are still inconceivable. Yet we can reach illuminating and even revolutionary generalizations about both sperm and brain. They are most illuminating and most revolutionary ... when we use what we know of heredity to enlarge what we know of intelligence.
[The Little Universe of Man, pp. 81-2]

Little has changed since Darlington wrote this.  If anything, the taboos have strengthened and the penalties for violating them have been toughened.  As the  'old guard' of modern genetics perished, few notable geneticists were prepared to take their place.  We are left with an embarrassed silence.

Further Reading:

The Darlington papers, some 240 boxes, are held in the Bodleian Library, Oxford (Reference code: GB 0161 C.D. Darlington papers).

The Haldane papers are housed in Bhubaneswar, Orissa, India.

Clark, Ronald JBS: The Life and Work of J.B.S. Haldane Hodder & Stoughton, 1968 (Oxford, 1984)
Darlington, C.D. "Race, Class and Mating in the The Evolution of Man" Nature, 3855 (1943), 315-319
Genetics and Man Penguin, 1953
"Psychology, Genetics and the Process of History" British Journal of Psychology 54 (1963), 293-298.
The Evolution of Man and Society Simon and Schuster, 1969
The Little Universe of Man George Allen & Unwin,  1978
Galton, Francis Hereditary Genius 1869
Inquiries into Human Faculty 1883
Haldane, J.B.S. The Inequality of Man Penguin, 1932
Soyfer, Valery Lysenko and the Tragedy of Soviet Science samizdat 1983 (Rutgers, 1994)