The Mismeasure of Man | Study Guide

Stephen Jay Gould

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The Mismeasure of Man | Chapter 3 : Measuring Heads: Paul Broca and the Heyday of Craniology | Summary



The Allure of Numbers

The war between monogeny and polygeny ended with broad acceptance of the theory of evolution in the scientific community after 1859. But belief in the original unity of humanity did nothing to weaken arguments for racism. In fact, monogenists then found new support in the growing use of numbers. "Evolution and quantification formed an unholy alliance," Gould writes, their union giving an aura of unassailable scientific "fact" to any racist claim that could be backed up by lots of numbers. The French neurologist Paul Broca did so with the field of craniometry, elevating the kind of skull measurement that Morton had done to a new level. But, just like Morton, Broca's prior beliefs influenced his interpretation of the data.

Gould writes at length about a flawed 1907 study on brain size done by Virginia physician Robert Bennett Bean in order to lay the groundwork for an examination of Broca's work. Bean said that his data showed that certain parts of the brain were larger in white males than in both women and black people. But when Bean's mentor at Johns Hopkins University tried to duplicate this work, he could not get the same results. Bean knew in advance to which race and sex his brains belonged whereas the mentor did not.

Gould sees Bean's story as an example of four claims in this book.

  1. Biological determinism seeks to prove not only that certain races are inferior, but that women and members of certain social classes are inferior as well.
  2. Numbers are used as tools to confirm existing biases.
  3. These biases also lead to flaws in experimental or statistical methods.
  4. Conclusions from these studies affect public opinion and policies.

Bean is an extreme example of bad science. But even careful craniometricians such as Broca were not immune to the distorting effects of their prejudices.

Masters of Craniometry: Paul Broca and His School

Broca was a professor of surgery who founded the Anthropological Society in Paris in 1859. Broca was confident that his craniometric data supported his conclusion that whites were intellectually superior to black people, although he said he found no joy in that. He proclaimed that facts must triumph over hopes or beliefs: "It is an axiom of all observational sciences that facts must precede theories." Gould thinks Broca's data was gathered with scrupulous care and greatly respects him for that. However, after reviewing his data Gould concludes that Broca violated his own rules. He did indeed put his culturally based assumptions first. Although his data was reliable, unlike Morton's, Broca was selective in what he measured. Then he "unconsciously manipulated" the data afterwards to fit his preformed conclusions, Gould says. Even more fundamental, Broca erred in failing to see that variation between individuals of any species is random and normal. It is not a sign of some underlying rank or hierarchy.

Broca looked beyond skull size or even brain weight to other markers that could show which race was closer to apes, measuring the length of the arm bones as well. But when that seemed to show that white arms were more like apes, he decided that was irrelevant. When the brains of "Mongolians" proved to be larger than those of white Europeans, Broca decided that when it came to size, only smallness mattered. Although a small brain was invariably associated with low intelligence, Broca claimed, a large brain did not necessarily indicate superior intellect. Since women, the poor, and darker-skinned peoples have the smallest brains, they are thus inferior.

Other followers of Broca made their case for the superiority of white males by measuring the brains of dead scientists and authors. Sometimes this tactic worked, as in the case of the great French scientist Georges Cuvier, founder of the fields of anatomy and paleontology. Cuvier had the heaviest brain of all until the Russian author Ivan Turgenev later surpassed him. But sometimes the results were disappointing. The American writer Walt Whitman had a relatively small brain—it later turned out that Broca's own brain was merely average in size. Broca explained the smaller-than-expected brains of other eminent men by attributing it to poor health or advanced age. When so many criminals were found to have large brains, Broca decided that execution by hanging caused the brains to swell.

Broca did not think that groups with smaller brains, such as women, were condemned to permanent inferiority. He did believe that improved education and social conditions could lead to increasing brain size over time, but he ran into a snag when he attempted to prove this by measuring the skulls from three Parisian cemeteries from three different centuries. When he didn't find the results he expected, he tried to explain this in various ways, but failed.

So, like Robert Bennett Bean in the United States, Broca measured the relative size of the front and back portions of the brain, stating that only the front portion was related to intelligence. (The portion of the frontal lobe where language is processed is still called Broca's area in his honor.) Broca concluded that whites had the largest frontal lobes. So when he found that prehistoric Cro-Magnon humans had larger skulls than modern Frenchmen, he was still able to pronounce the superiority of the French due to the larger frontal section of their skulls. He made similar rationalizations when other aspects of the skull seemed to indicate that black people were superior to whites. In other words, Gould writes, when the data did not confirm Broca's belief that whites were superior, he would change the rules by which he interpreted the data.


The craniometry practiced by Broca and others fell out of favor as the 20th century arrived. Some scientists who favored intelligence tests as a means of assessing superiority did work discrediting the results of men like Broca. In 1970 a South African anthropologist argued that studies have never demonstrated any difference in brain size between groups. This is because so many factors can affect the measurements. So even before the distorting effects of prior belief kick in, the physical measurements themselves have always been suspect.


Even today statistics are often used as weapons in debates about political and social issues. Numbers carry such an aura of authority that they are often wielded like bombs intended to completely obliterate an opponent's argument. As the cliché goes, "Numbers do not lie." Gould's point in this chapter is that although numbers themselves may not lie, they also do not interpret themselves. In order to draw any meaning from raw data such as numerical measurements, someone has to analyze them to learn what significance, if any, they reveal. All too often the preexisting beliefs or prejudices of the person performing that analysis cause them to misinterpret the numbers.

This is true even in the case of so-called experts such as Paul Broca and the other scientists who followed his lead. Gould expresses great respect for Broca's measurements themselves, saying that they were done carefully and appropriately. But Gould cannot respect the conclusions Broca drew from his measurements. It is so clear, from Broca's own writings, that he went to great lengths to force the data to fit his prior convictions. When his numbers didn't initially seem to prove his belief that white males were superior to everyone else, Broca either changed the scientific rules or neglected to apply them.

When presented with charts or graphs or statistics that purport to prove that some biological factor is the cause of a difference between groups of people, Gould cautions that it pays to be wary. Don't simply accept something as true because it comes from an expert. Look at the raw data itself, if possible—and carefully examine everything that person writes or says for beliefs that may be distorting the interpretation of the data.

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