In 1976 a Sydney doctor asked in print whether the new cooking oils were causing melanoma. His reasoning was simple. The sun had not changed. What the people were made of had. Hunters lived naked on the African savannah for 2 million years, on the equator, under the same sun all day. Egyptian labourers dragged limestone up the pyramids in a loincloth, in 45 degree heat. Greek athletes trained and competed stark naked at Olympia, in August, from dawn to dusk. Medieval families brought in every harvest of their lives with their faces, necks and arms turned to the July sun for 14 hours a day. Nelson's sailors worked the rigging stripped to the waist in the Caribbean. The palest people on earth, Scots and Irish, were shipped to Australia and cleared the bush by hand, under a sun their skin had never met. The Anzacs dug trenches at Gallipoli with their shirts off. Bondi Beach in 1935 was shoulder to shoulder with fair-skinned Australians, and the only thing anybody rubbed on was coconut oil. Not one of them owned a bottle of sunscreen, and melanoma was a medical curiosity. As late as the 1930s an American's lifetime odds were 1 in 1,500. Today they are nearer 1 in 50. The sun did not get 30 times stronger in 90 years. The fat changed. Sunflower, soybean and corn oil replaced butter and dripping, and linoleic acid began building up in human tissue, including the fat in and under the skin. Linoleic acid oxidises under ultraviolet light. Butter and dripping hold firm. In the lab, the more corn oil the mice were fed, the more skin tumours the same lamp produced. Australia never took up the question. In 1981 it launched a cartoon seagull telling everyone to slop on sunscreen. B. S. Mackie kept measuring. By 1987 the linoleic acid in Sydney's body fat had climbed well past its 1975 level, and the melanoma patients carried significantly more of it than the people without. Sunscreen sales have risen every decade since the seagull. So has melanoma. Office workers now get more of it than farmers and fishermen, who are in the sun all day. The sun has been up there for 4.5 billion years. Seed oil has been in the human diet for just over a century. Only one of them was ever put on trial.