Graeme Mitchison
Scientist and musician who found mathematical beauty in plants and worked with Crick on dreams
GRAEME MITCHISON, who has died aged 73, was a Cambridge mathematician and scientist of extraordinarily wide interests; as well as publishing in fields such as neuroscience, physics and molecular biology, he was a gifted pianist and an elegant writer credited by the novelist Ian Mcewan with “reverse engineering” a spoof Nobel Prize presentation address for the appendix to his tragicomic novel Solar (2010).
Such broad interests might have been expected to dilute his contribution to science. But, as suggested by the presence at his funeral of the previous and present Presidents of the Royal Society – Martin Rees (Lord Rees of Ludlow) and Venki Ramakrishnan – this was wide of the mark.
Mitchison worked with Horace Barlow on the neuroscience of vision; with Richard Jozsa he investigated “counterfactual computation” which he defined as a “process by which the result of the computation may be learnt without actually running the computer”, and he wrote numerous papers on pattern formation in plants including “Phyllotaxis and the Fibonacci series”.
This paper, published in Science in 1977, explained why spirals in pine cones, sunflowers and many other plants develop according to Fibonacci numbers (in mathematics the Fibonacci sequence – 1,1,2,3,5,8,13,21,34,55, 89, 144 etc – is characterised by the fact that every number after the first two is the sum of the two preceding ones).
The phenomenon, Mitchison concluded, follows as mathematical necessity from the combination of an expanding apex of a plant and a suitable spacing mechanism for positioning new leaves.
In later life Mitchison became affiliated to the Sainsbury Laboratory in the Cambridge University Botanic Garden, where he returned to his work on pattern formation in plant growth in the light of modern molecular genetic knowledge.
Mitchison attracted interest in the general press for a 1983 paper in the journal Nature, published with Francis Crick, the co-discoverer of the structure of DNA and a good friend, in which the two scientists challenged the Freudian assumption that dreams bear meaningful psychological messages which can be analysed on the psychiatrist’s couch.
They proposed that during a day the brain makes many more connections between brain cells than are needed for efficient thinking and memory. The function of the REM (rapid eye movement) phase of sleep, when most dreams occur, they suggested, is to purge the brain of these unneeded connections.
Their theory, they argued, explains some facts which Freudian theory cannot. For example, newborn infants have a great deal of REM sleep, but presumably suffer none of the psychological conflicts or upsetting impulses that Freudians claim lead to dreams. On the other hand infants have the same need as adults to rid the brain of accidental or meaningless connections, and thus they have dreams.
Most dreams, Crick and Mitchison observed, are never remembered – and that is as it should be, because remembering might strengthen neural connections that should be discarded. “We dream in order to forget,’’ they wrote.
Graeme Mitchison was born on August 26 1944 into a notable scientific, literary and political family. His father, Professor Denis Mitchison, was an eminent bacteriologist. His mother, Ruth Gill, was a consultant pathologist.
His paternal grandfather was GR “Dick” (later Lord) Mitchison, a barrister who would serve as Labour MP for Kettering from 1945 to 1964. His paternal grandmother was the novelist Naomi Mitchison, whose fantasy book Graeme and the Dragon (1954), featured her then 10-year old grandson as the protagonist. She was the daughter of the Edinburgh physiologist John Scott Haldane, who introduced canaries into British coal mines to detect carbon monoxide. Her uncle, Lord Haldane, was Lord Chancellor in the first Labour government of 1924, while the geneticist JBS Haldane was her brother and Graeme’s great uncle.
Mitchison attended East Sheen Grammar School and won a county scholarship to study Mathematics at New College, Oxford, graduating in 1965.
After taking a PHD in Pure Mathematics under Dr Graeme Segal at St Catherine’s College, Oxford, in 1969 Mitchison joined the cell biology division of the MRC Laboratory of Molecular Biology (LMB) in Cambridge. He was initially involved in investigating pattern formation with Michael Wilcox, who was studying filamentous bluegreen algae. The two men went on to describe the sequence of events leading to the formation of a spaced pattern of differentiated cells called heterocysts that carry out nitrogen fixation.
Later Mitchison published papers containing mathematical models which could explain the formation of vein patterns and leaf growth in plants.
The years 1980-82 were spent at the Salk Institute for Biological Studies, La Jolla, California, where Mitchison worked with Francis Crick, publishing several papers on the workings of the brain, including their paper on dreams.
Back in Cambridge, Mitchison joined Horace Barlow’s group in the university’s Physiological Laboratory working on the way that the brain relates the images from the two eyes to see in depth, proposing a radical alternative to the standard theory of binocular matching. He also worked on neuronal branching patterns – the “wiring” in the brain which keeps it working efficiently.
In 1995 he returned to the LMB as a programme leader in the Structural Studies Division and worked with Richard Durbin in applying pattern recognition techniques to biological sequences such as DNA and with Sarah Teichmann on evolutionary signals in bacterial proteins. He also became interested in quantum information and computing and in 2005 he joined Cambridge University’s Department of Applied Mathematics and Theoretical Physics to pursue these interests.
Away from the laboratory, Mitchison was a gifted pianist whose house on Maids Causeway was a centre of Cambridge musical life, where friends could come and listen to performances by up-and-coming young musicians. A musical group has now taken his name in memory – the Mitchison Ensemble. He also painted, climbed and travelled widely, including cycling trips to India and a trip to Mongolia with the anthropologist Dame Caroline Humphrey. A fearless risk-taker, he once crashed a paraglider into cliffs at La Jolla.
Mitchison was a generous man with a gift for friendship, and a much-valued mentor for many students and younger colleagues. For four years he gave houseroom to Pascal Khoo Thwe, a Burmese English Literature student and political dissident rescued from the jungles of Burma by the Cambridge don Dr John Casey. In his memoirs From the Land of Green Ghosts: A Burmese Odyssey, Khoo Thwe gave an affectionate account of Mitchison’s bachelor academic lifestyle, noting that while a gas stove kept the kitchen warm, “the other rooms were deliberately kept cold … only my room was heated – to a tropical temperature … Graeme slept in an austere room on the first floor.”
In later life Mitchison struck up a friendship with Ian Mcewan after meeting him on a yacht in the Galapagos. Mcewan, who was working on his novel Solar, asked Mitchison to check the physics of the final draft and to draft a Nobel presentation speech for the novel’s egomaniacal hero, Michael Beard. The result was described in one review as “a satire on exclusive collegiality”. With James Sherlock, Mitchison also performed a section of Rachmaninov’s Symphonic Dances for two pianos, for the soundtrack of the film of Mcewan’s novel On Chesil Beach.
Mitchison died of an aggressive brain tumour.
He is survived by his brother and sister.
Graeme Mitchison, born August 26 1944, died April 13 2018