By the time of the 1929 Cape Town meeting of the British Association Julian Huxley was working well with HG Wells and his son Gip. All three were as surprised at the goings-on at the British Association meeting as most others back in Britain. They were as determined as ever to keep open the pluralist approach that Tansley had been advocating, to be considered in conjunction with the new genetics without being drawn into the politics of eugenics. Then Huxley got the job of Secretary to the Zoological Society of London, running the zoological gardens in Regent’s Park and at Whipsnade Park. This was a controversial appointment, for the zoo had been run along very conservative lines where the Fellows retained a lot of power on how the place was run. Huxley quickly introduced charges for members’ guests and fought hard for it to open to the public on Sundays. Young people were encouraged for the first time with a new children’s zoo and the backroom research flourished. It was an exciting place to be in that lull before the war.      

The zoo canteen even became well-known to a small group for its exceptional English cooking. With the help of a professional chef called Philip Harben the Half Hundred Dining Club often met there for such rare delicacies as bison’s heart and silverside of antelope. These dishes were only available at culling times and members sometimes complained that there were “not enough middle-sized snakes” to produce the soup they wanted. Meanwhile, alone in his study on many dark nights that led up to the London blitz, Julian Huxley embarked on a serious project similar to what he had done so well before with The Science of Life. From a confusing disarray of knowledge, he had the skill to bring together a new case for understanding how evolution worked. Unknown to anyone at the time including himself, this work was to become one of the great climaxes of twentieth century science. Not only did it cover variation and natural selection but every topic bearing on the subject, from the biochemical basis of heredity to the evolution of consciousness, the effects of human cultural development and the problem of defining evolutionary progress. Some say it was also the last, and the lost, opportunity to save our planet from the environmental catastrophe that was soon to get underway.

Bernal, Zuckerman and Needham all served as science advisors during the war, and Bernal was particularly busy as advisor to Mountbatten. He tested several extreme proposals for landing aircraft and tanks in difficult places. One involved mixing wood chips on icebergs to make them into strong and transportable landing strips; another tested the strength of beaches with only thin coverings of sand over peat and salt-marsh, and their advice helped decide the location of the D-Day landings in Normandy. This was when Huxley and Haldane often took part in the popular war-time radio show The Brains Trust, together with others such as Gilbert Clark, Robert Boothby, Malcom Sargent, Arthur Bliss, William Beveridge and Jacob Bronowski.

Huxley remembered one question that completely stumped them. “It came from a young girl, who asked how a fly managed to land upside-down on the ceiling. The answer was provided much later by high-speed cinematography – the fly does not reverse and turn a back-somersault, but executes a sideways roll.” Such challenging broadcasts cheered-up millions of other dark nights during the black-out. Bernard Shaw, still campaigning against Darwin’s ideas, forty years after that back-stage party for Jekyll and Hyde and sent Huxley a post card in May 1942: “I listened in on Tuesday and thought you got mixed up between evolution and education. Education goes on for a lifetime: but the evolution of perhaps thousands of years is recapitulated and compressed into as many minutes by the foetus. ….  Biology is in a bad way. The Laboratory mind is more degenerative than malaria. The descent from Huxley, Darwin and Spencer – broken by Butler, Bergson and Back to Methuselah – to the simpleton Pavlov is a precipitous degringolade (Mrs Huxley will translate).”

After another broadcast later that year Shaw wrote to the editor of The Listener: “My friend Dr Huxley, in his broadcast on Charles Darwin, dismissed me from consideration as a biologist on the ground that I am “emotional”, offering as a sample a passage from one of my prefaces, which was recited by the actor who impersonated me in such a manner as to make it sound like the raving of a sentimental drunkard. “I am not the author of this passage. It is a quotation from the Canticle in the order for Morning Prayer entitled Benedicte, Omnia Opera. Dr Huxley is unacquainted with the Book of Common Prayer, having been brought up as a Natural Selectionist; but I shall be happy to lend him my copy if he desired to verify the quotation. “P.S. Darwin did not exclude the emotions from the biological field. He wrote a whole book about them which I read before Dr Huxley was born.”

Shaw held on as one of the last supporters of Lamarckian vitalism and always hit out at people like Huxley who he labelled as “materialists” believing in natural selection. While he was living this eclectic life-style, Huxley was busy thinking about how he would make as big a mark on the world of biology as his grandfather. With his experience of the experimental genetics that was still growing in the United States and parts of Europe, with his knowledge of systematic zoology and ornithology in particular, and with his unusual outlook on life, he was well-placed to do something big. He began in his Presidential Address to the zoologists at the 1936 meeting of the British Association, and called for the re-unification of all biology around Darwin’s theory of evolution. Enough was known then about mutation, recombination and selection to bury non-Darwinian theories.

Bateson had died in 1926 without resolving the mystery about mutation and Fisher’s group hadn’t made any break-through either. The time was ripe to build some new way out of this stalemate. Huxley did well to publicise the way natural selection works, with radio talks, lectures and books. He used two principles to get his main ideas across: that natural selection works through reproduction and mutation, and that with time it gives improved systems in nature. These were loaded expressions: reproduction involved the self-copying of genes, improvement was such a subjective notion yet concerned adaptation to change. Just as water changes from liquid to gas at a critical point, and other chemicals change their molecular organisation at different points, so, Huxley argued, organisms change their species at their own kind of critical point, making new species into real new entities. In contrast, he saw genera as strings of species descended from ancestors, products of history rather than something with their own dynamic, and he realised it was the environment that changed the critical point through geological time.

Another important feature that he emphasised was stability, the time between these changes of the critical points, the “persistence of types” and known now as “punctuated equilibria”. Then Huxley had a bit of timely good luck, an unexpected boost to these ways of uniting all the evolutionary evidence and it came from an unexpected source. He realised that if he was to bring a lot of different specialists together he needed a strong link between experimental biologists and the more classical taxonomists at museums, zoos and botanical gardens, so it was timely that the taxonomists were setting themselves up with a new society in May 1937. It was auspiciously named the Association for the Study of Systematics in Relation to General Biology and Huxley was invited to edit its first publication, The New Systematics. This gathered together state-of-the-art reviews from nearly every field of biology and set the scene for Huxley to take a strong lead in bringing all the players together.

One of these infant disciplines which had enormous importance in understanding evolution was cellular biochemistry. Hans Krebs (1900-1981) had been barred from his work in medicine at Hamburg in 1933 and settled in Sheffield in 1937. That was also when he determined the ten or more intermediates of the citric acid cycle that played a central part in the metabolism of all animals and plants that breathe oxygen for aerobic respiration. He discovered how this links to all of photosynthesis, fat metabolism, amino acid and protein chemistry, carbohydrate storage and nucleic acid chemistry. Krebs’ discovery of this single and universal pathway for respiration was of central importance to how species are related, but it was rarely realised and acknowledged outside his field. These biochemical reactions were important to keep cells working together and also occurred universally in all species, with only few refinements and exceptions. It was striking how most animal and plant cells all used these basic reactions to obtain, store and use energy, and that the bits inside cells such as chromosomes, nuclei, mitochondria and chloroplasts followed the same structural and chemical formats. It was also realised in the 1930s that most living cells have this same kind of modular architecture, essential if they are all related to one-another through the same tree of common ancestry.