Woman in Science / With an Introductory Chapter on Woman's Long Struggle for Things of the Mind

by J. A. Zahm

So far as civilized races are concerned, there can be no doubt that the absolute weight of the male is greater than that of the female brain. According to the investigations of seven of the most notable anthropologists, who have given special attention to the subject under consideration, and who, collectively, have carefully weighed many thousands of brains, the average brain weight of men in Europe is 1381 grams, while that of women is 1237 grams. This shows a difference between the average weight of the brain in man and woman of 144 grams.

But, if it must be conceded that the absolute weight of man's brain is greater than woman's, is it likewise true that the relative weight is greater? This is a question which demands an answer, as it is impossible to come to any just conclusion respecting the intellectual capacity of woman expressed in terms of brain weight, unless we can affirm with certainty that men's brains are relatively, as well as absolutely, larger than those of women.

Speaking of the relative weight of brain in man implies a term of comparison. Several methods of estimating the sexual proportions of brain mass have been suggested, but only two of them have met with any favor. These are determining the ratio of brain weight to body weight or body height.

According to the investigations of anthropologists of acknowledged authority, the average brain weight of woman is to that of man in England and France as 90 is to 100. The average stature of men and women in the same countries is as 93 to 100. This gives man an excess of brain weight over that of woman of something more than an ounce. But this slight difference in weight has been considered sufficient to constitute it "a fundamental sexual distinction." When, however, it is considered that men are not only taller but also larger than women, this apparent advantage of an ounce in favor of the male entirely disappears, and the result is that the relative amount of brain mass in the two sexes is practically equal.

Because of the manifest inaccuracy of the stature criterion, many eminent anthropologists have prepared to estimate sexual differences in brain weight by adopting the method based on the ratio of brain mass to body weight. According to this method, women are found to possess brains which are equal to or even somewhat larger than those of men. If the comparative excess of non-vital tissue in the form of fat in woman be eliminated and estimates be based only on the active organic mass of her body, as compared with the same mass in man, the excess of brain weight in woman over that in man will be still more marked.

A careful study, then, of the brain as a whole, far from proving woman's inferiority to man, rather proves her superiority. The same may be said regarding sexual distinctions based on certain parts of the brain.

Some years ago it was positively asserted that the development of the frontal lobe exhibited a pronounced difference in the two sexes. It was said to be much greater in man than in woman and was regarded as a distinguishing characteristic of the male sex. This was in keeping with the generally accepted assumption that this portion of the brain is the seat of the higher intellectual processes. Further investigation, however, showed that there was practically no sexual difference in the frontal lobe of the brain, or, if there was a difference, it was probably in favor of woman.

It has also become recognized that there is no valid reason for considering the anterior portion of the brain as the seat of the higher mental functions. It is possible, but in the present state of science it can neither be affirmed nor denied. So far as our present knowledge goes, it seems more likely that the whole of the brain, especially the sensori-motor regions of its middle part, have a part in mental operations. At all events, it can certainly be affirmed that Huschke's distinction of man and woman into homo frontalis et homo parietalis is utterly devoid of foundation in fact.

Many anthropologists have fancied that a certain index of the degree of intelligence is to be found in the convolutions of the brain. The tortuous foldings of the female brain, it is asserted, are less ample, less pronounced and less beautiful. "Behold," they exclaim, "a most positive evidence of inferiority." These men overlook the fact that certain animals, notably the elephant and divers species of cetaceans, have cerebral convolutions that are more complex than those of man. If, then, brain convolutions were, as claimed, a certain index of the degree of intelligence, the whale or the elephant, and not man—pace Shakespeare—would be "the paragon of animals."

But men of science are by no means at one on this alleged sexual difference in brain convolutions. On the contrary, there are many eminent physiologists and anatomists who contend that the superficies of brain convolutions in women is relatively greater than in men. For those who believe—and they are probably the majority at present—that the seat of mental activity is in the gray matter of the brain, this greater brain surface, due to its convolutions, would be a decided compensation for woman's relatively smaller brain volume.[98]