But Broca was still bothered. He could get around the low values, but he couldn’t raise them to unusual weights. Consequently, to clinch an unbeatable conclusion, he suggested with a touch of irony that Wagner’s post-Gaussian subjects may not have been so eminent after all:
It is not very probable that 5 men of genius should have died within five years at the University of Göttingen.… A professorial robe is not necessarily a certificate of genius; there may be, even at Göttingen, some chairs occupied by not very remarkable men (1861, pp. 165–166).
At this point, Broca desisted: “The subject is delicate,” he wrote (1861, p. 169), “and I must not insist upon it any longer.”
LARGE-BRAINED CRIMINALS
The large size of many criminal brains was a constant source of bother to craniometricians and criminal anthropologists. Broca tended to dismiss it with his claim that sudden death by execution precluded the diminution that long bouts of disease produced in many honest men. In addition, death by hanging tended to engorge the brain and lead to spuriously high weights.
In the year of Broca’s death, T. Bischoff published his study on the brains of 119 assassins, murderers, and thieves. Their average exceeded the mean of honest men by 11 grams, while 14 of them topped 1,500 grams, and 5 exceeded 1,600 grams. By contrast, only three men of genius could boast more than 1,600 grams, while the assassin Le Pelley, at 1,809 grams, must have given pause to the shade of Cuvier. The largest female brain ever weighed (1,565 grams) belonged to a woman who had killed her husband.
Broca’s successor Paul Topinard puzzled over the data and finally decided that too much of a good thing is bad for some people. Truly inspired criminality may require as much upstairs as professorial virtuosity; who shall decide between Moriarty and Holmes? Topinard concluded: “It seems established that a certain proportion of criminals are pushed to depart from present social rules by an exuberance of cerebral activity and, consequently, by the fact of a large or heavy brain” (1888, p. 15).
FLAWS IN A PATTERN OF INCREASE THROUGH TIME
Of all Broca’s studies, with the exception of his work on differences between men and women, none won more respect or attention than his supposed demonstration of steady increase in brain size as European civilization advanced from medieval to modern times (Broca, 1862b).
This study merits close analysis because it probably represents the best case of hope dictating conclusion that I have ever encountered. Broca viewed himself as a liberal in the sense that he did not condemn groups to permanent inferiority based on their current status. Women’s brains had degenerated through time thanks to a socially enforced underusage; they might increase again under different social conditions. Primitive races had not been sufficiently challenged, while European brains grew steadily with the march of civilization.
Broca obtained large samples from each of three Parisian cemeteries, from the twelfth, the eighteenth, and the nineteenth centuries. Their average cranial capacities were, respectively, 1,426, 1,409, and 1,462 cc—not exactly the stuff for a firm conclusion of steady increase through time. (I have not been able to find Broca’s raw data for statistical testing, but with a 3.5 percent mean difference between smallest and largest sample, it is likely that no statistically significant differences exist at all among the three samples.)
But how did these limited data—only three sites with no information on ranges of variation at a given time and no clear pattern through time—lead Broca to his hopeful conclusion? Broca himself admitted an initial disappointment: he had expected to find intermediate values in the eighteenth-century site (1862b, p. 106). Social class, he argued, must hold the answer, for successful groups within a culture owe at least part of their status to superior wits. The twelfth-century sample came from a churchyard and must represent gentry. A common grave provided the eighteenth-century skulls. But the nineteenth-century sample was a mixture, ninety skulls from individual graves with a mean of 1484 cc, and thirty-five from a common grave with an average of 1403 cc. Broca claimed that if differences in social class do not explain why calculated values fail to meet expectations, then the data are unintelligible. Intelligible, to Broca, meant steadily increasing through time—the proposition that the data were meant to prove, not rest upon. Again, Broca travels in a circle:
Without this [difference in social class], we would have to believe that the cranial capacity of Parisians has really diminished during centuries following the 12th. Now during this period … intellectual and social progress has been considerable, and even if we are not yet certain that the development of civilization makes the brain grow as a consequence, no one, without doubt, would want to consider this cause as capable of making the brain decrease in size (1862b, p. 106).
But Broca’s division of the nineteenth-century sample by social class also brought trouble as well as relief—for he now had two samples from common graves and the earlier one had a larger mean capacity, 1,409 for the eighteenth century vs. 1,403 for the nineteenth. But Broca was not to be defeated; he argued that the eighteenth-century common grave included a better class of people. In these prerevolutionary times, a man had to be really rich or noble to rest in a churchyard. The dregs of the poor measured 1,403 in the nineteenth century; the dregs leavened by good stock yielded about the same value one hundred years before.
Each solution brought Broca new trouble. Now that he was committed to a partition by social class within cemeteries, he had to admit that an additional seventeen skulls from the morgue’s grave at the nineteenth-century site yielded a higher value than skulls of middle- and upper-class people from individual graves—1,517 vs. 1,484 cc. How could unclaimed bodies, abandoned to the state, surpass the cream of society? Broca reasoned in a chain of surpassingly weak inference: morgues stood on river borders; they probably housed a large number of drowned people; many drowned are suicides; many suicides are insane; many insane people, like criminals, have surprisingly large brains. With a bit of imagination, nothing can be truly anomalous.
Front and back
Tell me about this new young surgeon, Mr. Lydgate. I am told he is wonderfully clever; he certainly looks it—a fine brow indeed.
—GEORGE ELIOT, Middlemarch (1872)
Size of the whole, however useful and decisive in general terms, did not begin to exhaust the content of craniometry. Ever since the heyday of phrenology, specific parts of the brain and skull had been assigned definite status, thus providing a set of subsidiary criteria for the ranking of groups. (Broca, in his other career as a medical man, made his most important discovery in this area. In 1861 he developed the concept of cortical localization of function when he discovered that an aphasic patient had a lesion in the left inferior frontal gyrus, now called Broca’s convolution.)
Most of these subsidiary criteria can be reduced to a single formula: front is better. Broca and his colleagues believed that higher mental functions were localized in anterior regions of the cortex, and that posterior areas busied themselves with the more mundane, though crucial, roles of involuntary movement, sensation, and emotion. Superior people should have more in front, less behind. We have already seen how Bean followed this assumption in generating his spurious data on front and back parts of the corpus callosum in whites and blacks.
Broca often used the distinction of front and back, particularly to extract himself from uncomfortable situations imposed by his data. He accepted Gratiolet’s classification of human groups into “races frontales” (whites with anterior and frontal lobes most highly developed), “races parietales” (Mongolians with parietal or mid lobes most prominent), and “races occipitales” (blacks with most in the back). He often unleashed the double whammy against inferior groups—small size and posterior prominence: “Negroes, and especially Hottentots, have a simpler brain than ours, and the relative poverty of their convolutions can be found primarily on their frontal lobes” (1873a, p. 32). As more direct evidence, he argued that Tahitians artificially deformed the frontal areas of certain male children in or
der to make the back portions bulge. These men became courageous warriors, but could never match white heroes for style: “Frontal deformation produced blind passions, ferocious instincts, and animal courage, all of which I would willingly call occipital courage. We must not confound it with true courage, frontal courage, which we may call Caucasian courage” (1861, pp. 202–203).
Broca also went beyond size to assess the quality of frontal vs. occipital regions in various races. Here, and not only to placate his adversary, he accepted Gratiolet’s favorite argument that the sutures between skull bones close earlier in inferior races, thus trapping the brain within a rigid vault and limiting the effectiveness of further education. Not only do white sutures close later; they close in a different order—guess how? In blacks and other inferior people, the front sutures close first, the back sutures later; in whites, the front sutures close last. Extensive modern studies of cranial closure show no difference of timing or pattern among races (Todd and Lyon, 1924 and 1925).
Broca used this argument to extricate himself from a serious problem. He had described a sample of skulls from the earliest populations of Homo sapiens (Cro-Magnon type) and found that they exceeded modern Frenchmen in cranial capacity. Fortunately, however, their anterior sutures closed first and these progenitors must have been inferior after all: “These are signs of inferiority. We find them in all races in which the material life draws all cerebral activity to it. As intellectual life develops among a people, the anterior sutures become more complicated and stay open for a longer time” (1873a, p. 19).
The argument of front and back,* so flexible and far-ranging, served as a powerful tool for rationalizing prejudice in the face of apparently contradictory fact. Consider the following two examples.
THE CRANIAL INDEX
Beyond brain size itself, the two most hoary and misused measures of craniometry were surely the facial angle (jutting forward of face and jaws—the less the better), and the cranial index. The cranial index never had much going for it beyond ease of measurement. It was calculated as the ratio of maximum width to maximum length of the skull. Relatively long skulls (ratio of .75 or less) were called dolichocephalic; relatively short skulls (over .8), brachycephalic. Anders Retzius, the Swedish scientist who popularized the cranial index, constructed a theory of civilization upon it. He believed that Stone Age peoples of Europe were brachycephalic, and that progressive Bronze Age elements (Indo-European, or Aryan dolichocephalics) later invaded and replaced the original and more primitive inhabitants. Some original brachycephalic stocks survive among such benighted people as Basques, Finns, and Lapps.
Broca disproved this popular tale conclusively by discovering dolichocephalics both among Stone Age skulls and within modern remnants of “primitive” stocks. Indeed, Broca had good reason to be suspicious of attempts by Nordic and Teutonic scientists to enshrine dolichocephaly as a mark of higher capability. Most Frenchmen, including Broca himself (Manouvrier, 1899), were brachycephalic. In a passage that recalls his dismissal of Tiedemann’s claims for equality between black and white brains, Broca labeled Retzius’s doctrine as self-serving gratification rather than empirical truth. Did he ever consider the possibility that he might fall prey to similar motivations?
Since the work of Mr. Retzius, scientists have generally held, without sufficient study, that dolichocephaly is a mark of superiority. Perhaps so; but we must also not forget that the characters of dolichocephaly and brachycephaly were studied first in Sweden, then in England, the United States and Germany—and that in all these countries, particularly in Sweden, the dolichocephalic type clearly predominates. It is a natural tendency of men, even among those most free of prejudice, to attach an idea of superiority to the dominant characteristics of their race (1861, p. 513).
Obviously, Broca declined to equate brachycephaly with inherent stupidity. Still, the prestige of dolichocephaly was so great that Broca felt more than a little uncomfortable when clearly inferior people turned up longheaded—uncomfortable enough to invent one of his most striking, unbeatable arguments. The cranial index had run into a stunning difficulty: not only were African blacks and Australian aborigines dolichocephalic, but they turned out to be the world’s most longheaded peoples. Adding insult to this injury, the fossil Cro-Magnon skulls were not only larger than those of modern Frenchmen; they were more dolichocephalic as well.
Dolichocephaly, Broca reasoned, could be attained in several ways. The longheadedness that served as a mark of Teutonic genius obviously arose by frontal elongation. Dolichocephalics among people known to be inferior must have evolved by lengthening the back—occipital dolichocephaly in Broca’s terms. With one sweep, Broca encompassed both the superior cranial capacity and the dolichocephaly of his Cro-Magnon fossils: “It is by the greater development of their posterior cranium that their general cranial capacity is rendered greater than ours” (1873a, p. 41). As for blacks, they had acquired both a posterior elongation and a diminution in frontal width, thus giving them both a smaller brain in general and a longheadedness (not to be confused with the Teutonic style) exceeded by no human group. As to the brachycephaly of Frenchmen, it is no failure of frontal elongation (as the Teutonic supremacists claimed), but an addition of width to a skull already admirable.
THE CASE OF THE FORAMEN MAGNUM
The foramen magnum is the hole in the base of our skull. The spinal cord passes through it and the vertebral column articulates to the bone around its edge (the occipital condyle). In the embryology of all mammals, the foramen magnum begins under the skull, but migrates back to a position behind the skull at birth. In humans, the foramen magnum migrates only slightly and remains under the skull in adults. The foramen magnum of adult great apes occupies an intermediate position, not so far forward as in humans, not so far back as in other mammals. The functional significance of these orientations is clear. An upright animal like Homo sapiens must have its skull mounted on top of its vertebral column in order to look forward when standing erect; fourfooted animals mount their vertebral column behind their skull and look forward in their usual posture.
These differences provided an irresistible source for invidious comparison. Inferior peoples should have a more posterior foramen magnum, as in apes and lower mammals. In 1862 Broca entered an existing squabble on this issue. Relative egalitarians like James Cowles Pritchard had been arguing that the foramen magnum lies exactly in the center of the skull in both whites and blacks. Racists like J. Virey had discovered graded variation, the higher the race, the more forward the foramen magnum. Neither side, Broca noted, had much in the way of data. With characteristic objectivity, he set out to resolve this vexatious, if minor, issue.
Broca amassed a sample of sixty whites and thirty-five blacks and measured the length of their skulls both before and behind the anterior border of the foramen magnum. Both races had the same amount of skull behind—100.385 mm for whites, 100.857 mm for blacks (note precision to third decimal place). But whites had much less in front (go.736 vs. 100.304 mm) and their foramen magnum therefore lay in a more anterior position (see Table 3.1). Broca concluded: “In orang-utans, the posterior projection [the part of the skull behind the foramen magnum] is snorter. It is therefore incontestable … that the conformation of the Negro, in this respect as in many others, tends to approach that of the monkey” (1862c, p. 16).
But Broca then began to worry. The standard argument about the foramen magnum referred only to its relative position on the cranium itself, not to the face projecting in front of the cranium. Yet Broca had included the face in his anterior measure. Now everyone knows, he wrote, that blacks have longer faces than whites. This is an apelike sign of inferiority in its own right, but it should not be confused with the relative position of the foramen magnum within the cranium. Thus Broca set out to subtract the facial influence from his measures. He found that blacks did, indeed, have longer faces—white faces accounted for only 12.385 mm of their anterior measure, black faces for 27.676 mm (see Table 3.1). Subtracting facial le
ngth, Broca obtained the following figures for anterior cranium: 78.351 for whites, 72.628 for blacks. In other words, based on the cranium alone, the foramen magnum of blacks lay farther forward (the ratio of front to back, calculated from Broca’s data, is .781 for whites, and .720 for blacks). Clearly, by criteria explicitly accepted before the study, blacks are superior to whites. Or so it must be, unless the criteria suddenly shift, as they did forthwith.
Table 3.1 Broca’s measurements on the relative position of the foramen magnum
The venerable argument of front and back appeared to rescue Broca and the threatened people he represented. The more forward position of the foramen magnum in blacks does not record their superiority after all; it only reflects their lack of anterior brain power. Relative to whites, blacks have lost a great deal of brain in front. But they have added some brain behind, thus reducing the front/back ratio of the foramen magnum and providing a spurious appearance of black advantage. But they have not added to these inferior back regions as much as they lost in the anterior realm. Thus blacks have smaller and more poorly proportioned brains than whites:
The anterior cranial projection of whites … surpasses that of Negroes by 4.9 percent.… Thus, while the foramen magnum of Negroes is further back with respect to their incisors [Broca’s most forward point in his anterior measure that included the face], it is, on the contrary, further forward with respect to the anterior edge of their brain. To change the cranium of a white into that of a Negro, we would have not only to move the jaws forward, but also to reduce the front of the cranium—that is, to make the anterior brain atrophy and to give, as insufficient compensation, part of the material we extracted to the posterior cranium. In other words, in Negroes, the facial and occipital regions are developed to the detriment of the frontal region (1862c, p. 18).