Theophilus Shickel Painter (1889–1969) was an American zoologist famous for his work on chromosomes. He became the distinguished Professor of Zoology at the University of Texas, and was its president during most of WW2 and until 1952.

By way of aside, during his presidency of the University he was named as official defendant in the landmark civil rights case Sweatt vs Painter. That legal stepping stone towards full integration of US education came about because one Hermon Sweatt had been denied admission to the University of Texas due to his race.1

Well before that, though, Painter was renowned for having given the world the official number of chromosomes in each human cell. In 1921 he first used sperm cells to make the count under the microscope. Sperm cells and egg cells each contribute half the number, so this would presumably make it easier to count what was, using the methods of that time, a fairly tangled appearance. He arrived at the figure of 24, and is recorded as having said, “I feel confident that this is correct”. Repeats of his experiment by others gave the same count, so the total number of chromosomes, it was decided, must be 2 x 24, i.e. 48.

Of course, the real number is actually 23 pairs, i.e. 46, not 48. But so powerful was the ‘authority’ of the distinguished Theophilus Painter, that this number was unchallenged for more than 30 years. According to BBC commentator Robert Matthews, “For years biochemists refused to believe humans possess 23 pairs of chromosomes”.2  Why? “Because it contradicted the claims” of this “influential American zoologist”. So, “many ignored the evidence of their own eyes rather than challenge the great man”.2….

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