The most promising ideas about evolutionary biology were kept alive by five brave men, and as with so many campaigns of those years tragedy came to many of their projects. But as well as some serious set-backs two of these men did help sort through the murky detail that had accumulated since Darwin’s death.

The soldiers were JBS Haldane, Ronald Fisher, Jan Smuts and Julian Huxley, while Arthur Tansley worked in munitions. As a group they were never close and they didn’t meet together. Huxley was a polite diplomat and could have been a discrete host, for only he had a relationship with all the others. Instead, they mostly thought and worked alone, though Fisher and Haldane had strangely close and parallel lives. They had similar backgrounds, similar age, schools, Oxbridge, and ended up as biologists at University College London, one was a Christian right winger and the other an atheist and to the left. Fisher the Christian saw God as a benign casino owner with what he called a “design by chance” policy, challenging humanity to work together by self-discipline to save the planet. This made it easy for him to explain natural selection by probability theory. Fisher and Haldane always worked on separate projects, and despite their strong rivalry there are no well-known stories that they ever seriously fell out. However, they did argue incessantly, and when they worked in the same building during the 1920s they were heard to disagree about anything and everything every tea-time.

Of the five warriors only Huxley and Tansley had trained as biologists: Smuts was a lawyer, Haldane a classicist, and Fisher a mathematician. Such intellectual variety enabled them to imbibe rich evolutionary diets, and the violent times cut out a lot of the pre-war rubbish, confusion and personal bickering. It was the time to review the best of what remained and use that to rebuild with fresh plans and techniques.

JBS Haldane (1892-1964), also known as Jack, said he had a good war. As Lieutenant Haldane he raided the German lines at night by throwing grenades into their trenches. As part of an aristocratic family of Scottish baronets, he had been brought up to relish fear and how to work with it, skills that he enjoyed showing off to his uncle who was Minister of War. He was also influenced by his eccentric father, the Professor of Physiology at Oxford, and they often used their own bodies as experimental animals. His mother told how, when Jack was eleven, his pet guinea-pigs were killed by a friend’s dog the day before he came home from Eton. He hated school and had been bullied there from the day he started: then he broke an arm and he discovered that his only defence was his academic brilliance. The tragedy with his guinea-pigs was especially frustrating to him because he’d been counting the progeny to give him precious data so he could test his equations that modelled their breeding. Then his father soon came up with some other new challenges that involved quite dangerous tests breathing toxic gasses. After one decompression experiment he suffered a perforated ear drum which left him somewhat deaf: “one can blow tobacco smoke out of the ear in question, which is a social accomplishment.”

Jack Haldane couldn’t wait to finish his finals exams at Oxford because he was so looking forward to trying out some of his physiology experiments in the real battleground. He joined up as a soldier with the Black Watch as soon as he graduated and went off to the front in Belgium with equipment to monitor respiration and other bodily functions affected by poisonous gas. Before the battle of Aubers Ridge in 1915 Rajah the Bomb, as he was known by his men, wrote to his father: “I am enjoying life here very much. I have got a most ripping job as a bomb officer.”  For Haldane, the war seemed to make little difference to the way he lived and thought in normal life; it was just the kind of work that was new and the company different. What most people thought to be uncomfortable and frightening he didn’t seem to notice.

The same applied for different reasons to Haldane’s great rival Ronald Fisher (1890-1962) who left university for work as a statistician in the City of London. This was not an easy thing for an eager young man to do in that troubled decade but even his good record as a part-time officer in the Territorial Army couldn’t prove that his eyesight was good enough for the recruitment board. Reluctantly he settled for teaching physics and mathematics to cadets and rented a cottage out in the country with his 17 year old wife so they could help the war effort by farming. It also gave him an ideal opportunity to fulfil his own political ideals: if you believed strongly in eugenics, and if you and your mate were healthy and intelligent, you had a duty to society to have a lot of children. It might even begin to help make up for the very high number of officers being killed.    

The quiet country evenings allowed them to concentrate on their work and Fisher continued to try to solve the problem that had kept Cambridge and London apart, the difference between evidence from single characters such as genes and their mutations and evidence from questionnaires about things like height and intelligence. Fisher wrote an article attempting to reconcile the differences between Cambridge and London, focussing on the use of new methods to analyse the data.

Similarly stretched in those times, but from a very different culture, Jan Smuts (1870-1950) was an Afrikaner who had become enough of a professional soldier to live with the new conflict in Europe as his normal routine. Earlier he had led raids in the Boer War, became a Unionist politician hoping to unite the country, was elected to join the government and served as Education Minister. By the outbreak of the First World War he was a General and so he led the British Army to take German East Africa in 1916 while in his free time he pursued his hobby as a field botanist. Already he had become a specialist in South African grasses and had supported a big survey of plants in South Africa, finding great pleasure in looking at nature in the vast African landscape. It was an interest he had enjoyed as a law student at Cambridge in the 1890s, going off for long walks making field observations of wild life in the fens. It was one of his few pleasures in those lonely years, the beauty of nature starkly contrasting with his attraction to some political mission in his homeland. These two apparently extreme parts of his personality were brought together by his actively creative mind as he developed a grand idea he called holism and which he later adapted to controversial ends.

In South Africa, botany had been a popular hobby for the white elite after the Boer War and Smuts wanted to share its wonder and variety as a national treasure. His vision was to compare his homeland’s great biodiversity with the range of human interests in culture and philosophy. It was what he called holism, and his hope as Education Minister was to bring that broad concept to unite all classes in the new nation. With an essay entitled An Inquiry into the Whole he argued against the tendency of most scientists to split things up into their component parts, preferring to see the system as a whole. It was an unpopular suggestion then, and with little very clear evidence that it might mean anything, so as with Fisher’s manuscript, another set of stiff referees agreed that it should not be published.

That was a pity because the manuscript contained some original ideas about uniting the ever-widening branches of the life sciences. He described these as “the external physical world of energy” and “the internal world of mind and spirit” and argued that these two parts of living systems were needed together, an indivisible unity of The Whole. It was a way of thinking that didn’t fit into war-torn Europe and so Smuts’ good ecological thoughts became lost in history. Something very much like them was to return almost a century later, too late to rescue the world’s natural environment.

Despite his unpopular manuscript, Smuts was a hero in Britain for very different reasons: not only for his military success in South West Africa but later in 1916 for his important advice to the war cabinet. Through those months he lived in the Savoy Hotel overlooking the Thames and the Palace of Westminster, but he found hotel life in the middle of a big city a “very severe strain”. It prevented him from “walking in the country in unity with nature and in quiet from human beings.” But the end of the war was in sight and he felt that Europe had had its day. With his belief that “Holism shall find healing in the Whole from the grievous wounds of the spirit, for the sick soul the Whole is the only Healer” he returned to South Africa as soon as he could. He wanted to promote his own version of holism and that was as good a place to do it as any other.

Meanwhile, the ecologist from Bloomsbury, Arthur Tansley, was 43 years old in 1914 and spent most of the war at the Ministry of Munitions in London. He also tried to keep tabs on the struggle between plants and their changing environment, and he monitored his long-term experiments near the Cambridge fenland that Smuts knew as a student. Tansley went further north to the Norfolk coast, and continued his surveys of woodlands and heath in other parts of Britain. He was doing something more than making static descriptions and lists of species that had become the normal way of conducting this field work. Instead he sought to compare these data alongside the physiological and genetic features of the organisms he saw, integrating as much as he could.

But even at home, war-time life was a hard struggle and at times it got Tansley down. He was especially traumatised by what had happened to so many young men in the war and he began to have restless nights haunted by vivid dreams. One of these influenced him deeply, causing him to develop an interest in the young discipline of psychology.

I dreamed that I was in a sub-tropical country, separated from my friends, standing alone in a small shack or shed which was open on one side so that I looked out on a wide-open space surrounded by bush or scrub. In the edge of the bush I could see a number of savages armed with spears and the long pointed shields used by some South African native tribes. They occupied the whole extent of the bush-edge abutting on the open space, but they showed no sign of active hostility. I myself had a loaded rifle, but realized that I was quite unable to escape in face of the number of armed savages who blocked the way.

Then my wife appeared in the open space, dressed entirely in white, and advanced towards me quite unhindered by the savages, of whom she seemed unaware. Before she reached me the dream, which up to then had been singularly clear and vivid, became confused, and though there was some suggestion that I fired the rifle, but with no knowledge of who or what I fired at, I awoke.

After a lot of thought about its meaning, the dream inspired Tansley to read the new medical journals and sort through what he thought was the most important work being done in psychology. Then he decided to write about this new way of understanding the human mind and after the war his New Psychology and its Relation to Life soon became a standard introduction to the subject. It sold by the thousand and was read by even more. Inevitably he drew comparisons between his two interests, one attracting much more attention and praise than the other. Only a few specialist scientists read his ecological work in as much detail and the relatively poor response drew him away from ecology towards psychology. It was a challenge that kept attracting those many people still wanting to know what makes humans unique.

The fifth warrior, more an adjudicator, was the 1909 zoology graduate from Oxford, Julian Huxley (1887-1975). He was a much more relaxed and rounded character than the others and even at Eton he had a happy time. Haldane remembered the five-year-senior Huxley trying to cheer him up by giving him an apple, a rare act of kindness. In the spirit of his important grand-father TH Huxley, well-known as “Darwin’s Bulldog”, Julian studied zoology at Oxford and then stayed on to study water birds. With that pedigree and background he was soon invited to set up the biology department at Rice University in Texas. When he first arrived in America in 1912 Huxley visited Harvard and met Sewall Wright, a modest mathematician looking for evolutionary trends and working on guinea pig data.

Among the explanations for some of these was one that all the characters he had chosen were controlled by genes on the same chromosome. These concepts of genes as particles that coded for a character were pretty advanced breakthroughs for the times, and to find evidence for their location on one particular chromosome was even more staggering. But Wright was cautious as well and he wasn’t going to shout about that possibility until he was sure.       

Likely as not Wright mentioned the new discoveries when Julian Huxley passed through on his way to Texas, but Huxley was also a tactful listener and he was hearing a lot of other exciting new ideas on that journey. The work there meant that he missed joining the war at first but the call to arms was strong and he came back to join the Intelligence Corps. He wrote of being pleased to feel physically fit and then: “In the spring we were sent to a camp at Upstreet, near Canterbury. I remember riding about the peaceful Kentish lanes, lined with white May bushes and pink-flowering horse-chestnuts, in strange contrast to the distant boom of heavy artillery from across the Channel.”

These different war-time experiences had similar effects on all these scientists, focussing their outlook on science to seek clearer and more objective targets. The pain of their friends’ deaths, their own guilt and loneliness as survivors was intense. Haldane and Smuts, the toughest of the group before the war, retained that aggression and arrogance, while Fisher became even more committed to eugenics with its even wider link to facism. They were all hardened by that war and all five of them had developed strong political aims that were to influence their work for the rest of their lives.