After that Great War, Europe was left stunned more than ever before. It was a major social catastrophe and it caused many people to change their lives dramatically. One who reacted with deep insight was the ecologist Arthur Tansley, apparently secure in academia after his recent election to The Royal Society. But still troubled by the war and the haunting dream, he decided to resign his lectureship at Cambridge and move to Vienna, with his family, for intensive psychoanalysis with Sigmund Freud.

That experience itself also had a profound impact on Tansley and he returned with new ideas for both psychology and ecology: “We must never conceal from ourselves that our concepts are creations of the human mind which we impose on the facts of nature.” Tansley was concerned at the high numbers of “feeble-minded” incarcerated in asylums to stop them contributing to national degeneracy by breeding. He had been particularly horrified by one young boy being detained for stealing a postal order and committed to a mental institution. Juvenile courts regularly institutionalised their charges for long periods and called them “morally defective”. He had a strong memory of Bloomsbury’s working class life and his rescue by the Great Ormond Street Working Men’s College.

Meanwhile, Tansley was working away quietly on gathering data from a few selected dynamic environments, listing the local movements of plant communities and checking changes in weather and species frequency. This went on to his idea of a complete “ecosystem” in the early 1920s though he didn’t coin the word until 1935. He was joining bits of his Vienna experiences of human community with his knowledge of plant communities, how separate individuals with independent powers of existence, lived together through different stages of growth and reproduction. Like Smuts’ holism, this eventually meant taking the basic laws of physics and chemistry into the realms of basic biology and then to the complexity of the human mind. They were adventures into the unknown that involved all of science and more beyond.

One of Tansley’s acquaintances was Ronald Fisher, desperate to become his own master after the war. He rejected the suggestion of his hero Pearson that they worked together at University College and quickly found the right opportunity at Rothamsted Experimental Station. Population genetics, experimental genetics and the systematic description of species were topics that needed to be brought together, and Fisher attempted to join Darwin’s natural selection with Mendel’s genetic ratios, helped by the pre-war realisation that gene particles lined up on the chromosomes. Fisher considered all the mathematical and statistical support for that model and showed for the first time that selection was the only way in which the process could be explained. Evolution couldn’t just be driven from inside the organisms: it needed a push from outside in the environment, one that led to the kind of small-scale continuous variability that Mendel’s recombinations explained so well. That explanation also meant that selection happened on a huge scale, between every organism in all places at all times, persistently testing the way forward and each time choosing the best option

Fisher’s mathematical insight drew comparisons between this style of evolution and the second law of thermodynamics. “Both are properties of populations, or aggregates, true irrespective of the units which compose them; both are statistical laws; each requires the constant increase of a measurable quantity, in the one case the order of a physical system, and in the other the fitness …. of a biological population.” Malthus’s warnings a hundred years before were always at the back of his mind, and his mission after the war was to do something about that.

     Fisher’s six daughters

This challenge led him to go too far and he spoiled his reputation in a book called The Genetical Theory of Natural Selection. In the spirit of the time, and doing himself no long-lasting favours, Fisher used the last part of the book for a long justification of the eugenics practices that he favoured so strongly. “The deductions respecting Man are strictly inseparable from the more general chapters.” He believed that industrial society was in decline due to “social promotion of the relatively infertile” and that the higher reproductive rate of less worthy classes will swamp the superior classes. His chapters carried statistical evidence for that view and it continued to attract support throughout the decade.

Two years after Fisher’s work was published, JBS Haldane came along with The Causes of Evolution, an easier book to read in which all the mathematics was relegated to the appendix. Like Fisher’s story, Haldane’s showed the power of natural selection and he began in characteristic mood: “I can write of natural selection with authority because I am one of the three people who know most about its mathematical theory.” Presumably the other two were Ronald Fisher and Sewall Wright. So the study of population genetics began, the mathematics of patterns of change coming from large numbers of individuals living together in the same community. Many biologists didn’t understand the mathematics, but a main reason for the intellectual movement they had accidentally created was to bridge these differences.

Although Haldane strongly rejected Lamarckian trends he did leave open the space for some evolution to happen by means other than natural selection. Hybridisation and some large mutations could make new species and Haldane urged that other processes may explain even more. He had plenty of evidence that “degeneration is a far commoner phenomenon than progress” and is usually hard to spot because it leads to extinction. From the fossil record he noticed “at any given evolutionary level we generally find one or two lines leading up to it, and dozens leading down”.

This kind of division within the biological community, between the rigid fixers and the more artistic flexers, was to continue for many years and was going to get much wider before anyone spotted the difficulties. But both sides needed to gain more knowledge about themselves before they could share their similarities and find out that way just how evolution worked. The two World Wars also kept scientists on these separate tracks, rigid armaments relied on a strong force of hard-nosed mathematicians, physicists and chemists. The more vague environmental sciences such as the new ecology and palaeontology didn’t stand much of a chance. Tansley and Huxley would have to wait.

Eugenics gave a very different outlook for all life on the planet and Fisher was hell-bent on exploiting biology in that single direction. He likened natural selection to the working of a casino where the odds were set for its own success. In his game the losers were equivalent to an extinct species, and the far right were the winners, supporting the casino owner who was only too pleased to let science make up the rules. Never one for philosophy or history, Fisher believed there was little new “that would not stand if the world had been created in 4004BC”.

Already a government committee had been set up to recommend how to sterilise the ‘feeble-minded’ in England and Wales where a quarter of a million people were classified as ‘mental defectives’ and suggestions had been made that they were suitable candidates for voluntary sterilisation. Some members of the committee thought that “Broadly speaking stupid people will produce stupid children” though Haldane and Hogben explained there was no certainty about that and that environmental factors were also likely to be a cause. The committee rejected compulsory sterilisation though even Haldane agreed with their conclusions: “Biologists may legitimately demand that a proportion of mental defectives should be prevented from breeding”.

Another popular debate between the two world wars was stimulated by Arthur Keith’s proposition that humans would become extinct without competition, and that meant war was necessary. Keith was an anatomist and anthropologist and wrote articles in the popular press advocating physical struggle and conflict as a vital biological characteristic.

In 1927 he told the British Association that cultural differences provide a mental barrier to social groups, suggesting that territorial behavior is a strong force in human evolution. He saw scientific and political merit in his idea of an ‘in-group’ and the less favoured ‘out-group’.

That view had been expressed earlier by a Prussian General, Friedrich von Bernhardi, in 1912, and several biologists agreed that it might be a possibility. Herbert Spencer had promoted the idea with his phrase “the survival of the fittest” and many in Europe during the 1920s and 30s believed that war played a role in this kind of biological process. They believed that the individuals and communities that survived were fitter in an evolutionary sense than those who died. This argument got tied up with some of the views of the eugenicists, inevitable consequences of those frightened times.

A forceful opponent of Keith was Joseph Needham, an influential member of the Cambridge left. He deplored the way that phrases such as “the struggle for existence” and “survival of the fittest” had become “the stock-in-trade of the man-in-the-street”, arguing that they were from old Victorian attitudes, then taken in by the public as part of their justification for joining-up to the armed forces. Keith continued with the idea that it was simply nature’s way of controlling populations, but the left-wing scientists would have none of that and instead sprang on to the offensive with their positive eugenics programme. Julian Huxley aimed for “the virtual elimination of the few lowest and most degenerate types” and he argued that biology should be the chief tool for rendering social politics.

The Huxley brothers called for some different thinking as part of a strategy towards the best interests of the planet earth and the human race. It involved a universal rhythm within earthly life, something they had been talking about for the last decade. As premier intellectuals they felt a responsibility to see to it that anything like the tragedy of the First World War did not happen again and that knowledge of the common features for all biodiversity might stop humanity being dragged down into the same mud. And from their family tradition, their grandfather’s smile beaming down on them constantly, Aldous and Julian had plenty more expected of them. Even those sceptical of Darwin’s ideas, broad minded men like Lawrence and Shaw, had their influence on Julian Huxley. More than most other scientists he was the cautious centrist, enjoying the foundations of Smuts’ holism very much within the fairness and functionalism of the English tradition. So prepared, Huxley went on to give another lecture that year in which once again he considered some of these wider aspects of his world view for our own species.

He called the lecture Eugenics and Society and repeated his call for a new Social Science to find ways to improve the living standards in the poorer parts of human communities, promote policies to favour more middle class babies and to discourage large families for the poor. But despite these hopes and concerns for a joined-up future it was hard in the 1930s to see any exciting new trends developing in biology and the evolution of life. Things were on hold, digesting the full impact of genetics, natural selection, cellular biochemistry and ecology as they became mixed together, waiting for their union to be approved and their significance understood. Krebs advances in biochemistry set an example against this pessimism that appealed to the Huxleys.

Meanwhile, even the attention of evolutionary biologists was directed to ways of trying to avoid war with the racist Nazis.  The League of Nations asked if “biology can end war?”, naïve in the view that war served some biological purpose. They thought that biologists still argued for some sort of “struggle for existence”, especially those who read Sir Arthur Keith’s regular articles in The Daily Mail, ostensibly about his subject, anthropology. He delighted his readers with his belief that Piltdown Man was a valid record of British supremacy and that it was important for humans to struggle to survive. Julian Huxley and many others tried to explain that there was no such scientific explanation, either of Piltdown Man or Nazi supremacy, but Keith held his ground against these scientists who he dismissed as left-wing extremists. It was a point well-made when Communist Party members such as the biologist Joseph Needham spoke publicly against Keith’s interpretations. “These men have deserted their heroes like Herbert Spencer and even Thomas Huxley” Keith argued, reminding his readers that in biology, both groups as well as individuals compete to be part of a healthy community: surely that validated war as part of the process of social evolution? Even Keith’s bitter enemy Haldane had urged in a lecture “that a proportion of mental defectives should be prevented from breeding”, while Sigmund Freud commented that violence was a character of the whole animal kingdom “from which men have no right to exclude themselves.”

These were still sensitive topics in those years when the Soviet experiment was just beginning and many biologists hoped that population might be controlled by eugenics. Some eugenicists even saw method in the madness of the First War that the weak were overtaken by the strong, but the large number of officers who died weakened their argument. By 1936 the support for voluntary sterilization of the less valuable members of society was on the wane and Pip Blacker, the Secretary of the Royal Zoological Society, thought it was all “a biological crisis unprecedented in the history of life”.