American biologist and co-discoverer, with Francis Crick and Maurice Wilkins, of the double-helix structure of DNA. He died on November 6th 2025, aged 97.
Watson grew up in Chicago, where as a boy he wanted only to watch birds. His interest shifted to genes after reading Erwin Schrödinger's "What is Life?" He studied at university but spent years avoiding the chemistry that seemed essential to his field.
In 1951, at a lecture in Naples by the physicist Maurice Wilkins of King's College, London, Watson saw an X-ray diffraction photograph of DNA that strongly suggested its molecule had repetitive motifs. He went on to work at the Cavendish Laboratory in Cambridge with the physicist Francis Crick. Their chief competitor was Linus Pauling at Caltech.
Watson persuaded Wilkins to show him a key X-ray photograph without seeking the permission of the crystallographer Rosalind Franklin, who had taken it. Watson and Crick determined the double-helix structure of DNA in 1953, showing that two twisting sugar-phosphate chains were linked by chemical bases forming alternate pairings of adenine with thymine and guanine with cytosine. As they laid out in Nature, the pairing "immediately suggests a possible copying mechanism for the genetic material."
Watson, Crick and Wilkins won the Nobel prize for physiology or medicine in 1962.
After 1953 most of Watson's work was in the United States. He led Harvard's molecular-biology department from 1961 to 1976. He first came to Cold Spring Harbor Laboratory in New York in 1947, when it was like a run-down summer camp; under his guidance it became a first-class centre of genetic research, especially into cancer.
Watson gathered scientists for the human-genome-mapping project, first meeting in 1986, and became its first director. He was the second person to have his genome fully sequenced, publishing the results free online in 2007. In the early 1990s he argued against the head of the National Institutes of Health that genes should never be patented.
His second son Rufus, born in 1970, developed schizophrenia, which sharpened Watson's interest in the treatment of mental illness. Watson's vivid 1968 book on the DNA discoveries, "The Double Helix" (originally titled "Honest Jim"), caused wide offence; both Crick and Wilkins persuaded Harvard not to publish it. He later expressed controversial views on women's intellectual abilities and the IQs of black people, among other subjects. His emeritus positions at Cold Spring Harbor were stripped as a result.
In 2014 he sold his gold Nobel medal for $4.8m; the buyer at once returned it to him.
Life is like a tin of sardines. We're, all of us, looking for the key.