I bought a copy of Wilfrid Le Gros Clark’s autobiography, Chant of Pleasant Exploration, when I was a junior doctor, but I was pleased to see a very clean copy in a secondhand bookstore in La Jolla in southern California. It was priced higher than I was willing to pay, and the miser in me was putting it back on the shelf when I noticed it had been inscribed by the author. I realized that although I must have read many hundreds of pages of Le Gros Clark’s writings, I had never before seen his hand-writing. He was meticulous in his writing and research, so Le Gros Clark’s small, neat, copper-plate script, should not have come as a surprise, but it did. It also reminded me how little, these days, one sees hand-writing. At school we were made to learn ‘proper’ hand-writing and, given my own poor hand-writing, my colleagues and students will be surprised to learn that I won third-prize in a national hand-writing competition organized by The Children’s Newspaper. But back to the inscription (see below). It reads, “To my friend Jacob Bronowski – with grateful memory for his help in disentangling myself from an artful controversialist and leading to my subsequent vindication.” Thereby hangs a tale that is part of the history and folklore of paleoanthropology.
The “artful controversialist” Le Gros Clark refers to was Solly Zuckerman. In 1934 Le Gros Clark was elected to the Dr. Lee’s Professorship in Anatomy at the University of Oxford, and Zuckerman was among the talented young scientists he recruited to join him. Zuckerman, a South African by birth, was medically-qualified, but he never went into medical practice. Instead, he studied primate reproduction at the Zoological Society of London; his findings were published in 1931 in The Social Life of Monkeys and Apes. Even before he arrived in Oxford, Zuckerman’s forceful personality, self-confidence and charm had marked him out as a force to be reckoned with. It also made him socially the polar opposite of Le Gros Clark, who, perhaps in part because he stammered, was shy, quiet and introspective.
Initially all went well enough for them to collaborate on a paper about the endocranial morphology of the chimpanzee (Le Gros Clark et al., 1936), but by the beginning of WWII the difference in their personalities and philosophies had begun to reveal itself. Le Gros Clark had been greatly affected by WWI. He had a harrowing time in the trenches as a young officer in the Royal Army Medical Corps, and by the end of the war he had lost one brother, and had seen another brother blinded on the final day of hostilities. In effect he became a pacifist. Zuckerman, on the other hand, came into his own during WWII. In 1939 he had joined the aristocracy by marrying the daughter of the Marquess of Reading, a marriage that provided him with both wealth and influence. Soon after the outbreak of WWII Zuckerman was drawn into what became known as ‘Operations Research’. For him, this included a range of projects, including testing which bombing strategies wrought most havoc (i.e., damage and injury), what was the best protection from blast injury, etc. In 1939 Zuckerman was appointed to the Sands Cox Chair of Anatomy at Birmingham University, but he did not take charge of the Anatomy Department there until his work on the war effort ended in 1946.
In December of 1946 Le Gros Clark visited South Africa to see at first hand the fossils that Broom, Robinson and others had been recovering from cave sites in and around Johannesburg. Le Gros Clark had initially been skeptical of the claims by the South African scientists that these fossils represented close relatives, if not ancestors, of modern humans, but his careful inspection of the evidence converted him from skeptic into supporter (see ‘Sideways Look’ 'Publications That Made a Difference: No. 1: ‘Sometimes Clout Matters'). Zuckerman, however, remained deeply skeptical of the claims and in April 1950 he wrote a letter to Nature (Zuckerman 1950a) in which he summarized the results of what then was still an unpublished analysis carried out with Eric Ashton, a junior colleague of Zuckerman’s at Birmingham (Ashton and Zuckerman 1950a and b). Zuckerman reported in the letter that of seventy-five dental characters of Plesianthropus and twenty-six dental characters of Australopithecus prometheus, “none differed from the orang-outang” (ibid, p. 652). Later in the letter he suggested that the fossil hominin teeth were even less like those of modern humans than were the teeth of the orang-outang. In short, he thought the South African fossils sampled apes, not hominins.
In the first of the two papers published at the end of August, Ashton and Zuckerman presented their comparative data (Ashton and Zuckerman 1950a), and in the second they compared the fossil data with their comparative great ape sample. Making much of the fact that they had used “appropriate statistical methods” (Ashton and Zuckerman 1950b, p. 485), they included a citation from Le Gros Clark’s long 1947 paper in the Journal of Anatomy in which he states, “there can be no question of any close affinity of the Australopithecinae with the modern Anthropoid apes.” They contrast this with their statistically-based conclusion that, “supposed divergences in shape and size from the apes have little, if any, foundation in fact” (ibid, p. 517). They suggested that there was no fossil hominin tooth from the sites in South Africa whose crown dimensions could not be accommodated in one, or other, of the extant anthropoid apes.
Between the publication of Zuckerman’s letter in April, and the publication of the Ashton and Zuckerman back-to-back papers in August, in a letter to Nature published in June Le Gros Clark (1950a) pushed back against Zuckerman, complaining that the latter’s reliance on a few linear measurements of the tooth crowns (he referred to them as “isolated abstractions”) ignored the, “total morphological pattern presented by the dentition” (ibid, p. 894). He went on to state, “no similar combination of all these hominid features together has been found in the dentition of any of the anthropoid apes” (ibid, p. 894). Le Gros Clark’s point was that although you might be able to find one of the linear dimensions of a fossil tooth in one of the individuals in the comparative anthropoid samples, you never found in the same ape individual the combination of the dimensions and morphology seen in the hominins. In a frosty response a month later, Zuckerman (1950b) suggests that, “Prof. Le Gros Clark seems to have misunderstood the point of my communication” and that the object of his own note was to show that, “adequate comparisons by proper statistical procedures” fail to show that, “the South African Australopithecine apes differ significantly in size and general shape from those of existing apes” (ibid, p. 158).
In November, Le Gros Clark (1950b) countered with line drawings of the dc and dm1 (ibid, p. 792) that emphasized how different the fossils are from the apes, but in his obviously irritated response Zuckerman (1950c) contrasts his own “facts” (i.e., statistics) with, by inference, Le Gros Clark’s recourse to drawings to illustrate “qualitative characteristics” (ibid, p. 953). The debate then changes venue, with Le Gros Clark publishing a note published in Man, the journal of the Royal Anthropological Institute, restating the case for considering the “total morphological pattern” (Le Gros Clark, 1951a, p. 19), followed by a note from Zuckerman (1951) arguing for the primacy of “modern biometrical and statistical methods”. Later, also in Man, Ashton and Zuckerman (1951a) counter with metrical data for the deciduous dentition showing that statistical methods can sort the deciduous tooth crowns of modern human from those of anthropoid apes.
Jacob Bronowski comes onto the scene in November, 1951. I remember him as the charismatic presenter of The Ascent of Man, but when he and a colleague, W.M. Long, came to the aid of Le Gros Clark he was the Director of Research at the National Coal Board. Coincidentally, like Zuckerman, he had also been involved in ‘Operations Research’ during WWII, and it would have been remarkable if they had not known of each other in that context. Originally a brilliant mathematician, and later a biologist, in 1964 Bronowski became the Associate Director of the Salk Institute (hence the appearance of books from his library at a bookshop in La Jolla). Zuckerman has been described as a polymath, but Bronowski really was a polymath, for he wrote authoritatively about literature as well as science.
It is worth quoting verbatim from the Bronowski and Long (1951) letter to Nature. They refer to the Ashton and Zuckerman analyses as “piecemeal tests”, and make a point still made to graduate students today, that, “a bone or a tooth is a unit: it is not a discrete assembly of independent measurements”, so to compare measurements one by one, as Ashton and Zuckerman did, they suggested, “is both inconclusive and misleading” (ibid, p. 794). The latter is the case because, “tests based on dimensions which are correlated are themselves not independent, and little is gained by accumulating them”. They go on to say that the, “right statistical method must treat the set of variates as a single coherent matrix” and they suggest that the correct technique under these circumstances is “multivariate analysis” (ibid, p. 794). They go on to set out the results of what I believe is the first application of multivariate analysis to paleoanthropology, which suggested that the deciduous canines from Taungs and Kromdraai, “do not belong to the chimpanzee group” (ibid, p. 794). The same authors published a longer version of their argument, with more information about multivariate analysis, in the American Journal of Physical Anthropology in the following year (Bronowski and Long, 1952).
Zuckerman sought his own statistical advice from Frank Yates and Michael Healy, both then at the Rothamsted Experimental Station (Yates and Healy, 1951). In 1933 Yates had succeeded Ronald Fisher as the Head of Statistics (N.B., Michael Healy helped me with multivariate analysis during my PhD research). However, when the two statisticians repeated Ashton and Zuckerman’s analyses they discovered that the latter had made a mistake in their calculations. The mistake resulted in them under-estimating, by a factor equal to the square root of two, the differences between the fossil hominin teeth and the teeth of the anthropoid apes (Ashton and Zuckerman, 1951b). Thus, Ashton and Zuckerman were embarrassed on two fronts. They had not only used an inappropriate statistical technique, but they had also made a basic mistake in the calculations they had performed. Zuckerman’s nose was bloodied, and apart from the occasional review, he retreated from any involvement in paleoanthropology.
Le Gros Clark’s inscription was ‘spot on’; Bronowski did vindicate his anatomically-based assessment of the fossil hominins from southern Africa.
I thank Matthew Goodrum for telling me that Jesse Richmond has written at greater length about this episode (Richmond, 2012).
References
Ashton, E.H and Zuckerman, S. (1950a) ‘Some Quantitative Dental Characters of the Chimpanzee, Gorilla and Orang-Outang’. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 234 (616): 471-484.
Ashton, E.H and Zuckerman, S. (1950b) ‘Some Quantitative Dental Characters of Fossil Anthropoids’. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 234 (617): 485-520.
Ashton, E.H and Zuckerman, S. (1951a) ‘Some Dimensions of the Milk Teeth of Man and the Living Great Apes’. Man, 51: 23-6.
Ashton, E.H and Zuckerman, S. (1951b) ‘Statistical methods in anthropology’. Nature, 168: 1117-8.
Bronowski, J. and Long, W.M. (1951) ‘Statistical methods in anthropology’. Nature, 168: 794-5.
Bronowski, J. and Long, W.M. (1952) ‘Statistics of discrimination in anthropology’. American Journal of Physical Anthropology, 10 (NS) No. 4: 385-394.
Le Gros Clark, W.E. (1950a) ‘South African Fossil Anthropoids’. Nature, 165: 893-4.
Le Gros Clark, W.E. (1950b) ‘South African Fossil Anthropoids’. Nature, 166: 791-2.
Le Gros Clark, W.E. (1951) ‘Comments on the Dentition of the Fossil Australopithecinae’. Man, 51: 18-20.
Le Gros Clark, W.E. (1968) Chant of Pleasant Exploration. Livingstone: Edinburgh and London, pp. 1-250.
Le Gros Clark, W.E., Cooper, D.M. and Zuckerman, S. (1936) ‘The Endocranial Cast of the Chimpanzee’. Journal of the Royal Anthropological Institute of Great Britain and Ireland, 66: 249-268.
Richmond, J. (2012) ‘Discipline and Credibility in the Post-War Australopithecine Controversy: Le Gros Clark Versus Zuckerman’. History and Philosophy of the Life Sciences, 34: 43-78.
Yates, F. and Healey, J.R. (1951) ‘Statistical methods in anthropology’. Nature, 168: 1116-7.
Zuckerman, S. (1950a) ‘South African Fossil Anthropoids’. Nature, 165: 652.
Zuckerman, S. (1950b) ‘South African Fossil Anthropoids’. Nature, 166: 158-9.
Zuckerman, S. (1950c) ‘South African Fossil Anthropoids’. Nature, 166: 953-4.
Zuckerman, S. (1951) ‘Comments on the Dentition of the Fossil Australopithecinae’. Man, 51: 20.
