In her compulsively readable Inferior: How Science Got Women Wrong - and the New Research That's Rewriting the Story, the British science writer, Angela Saini, tells us of a 2012 study at Yale University in which over a hundred scientists were asked to assess applications submitted for the post of laboratory manager. Every (fictional) curriculum vitae was identical, but with a twist: half were submitted under a female name and half with a male one. Scientists, even women scientists, overwhelmingly chose 'male' CVs over those supposedly submitted by female candidates. "Prejudice is so steeped in the culture of science... that women are themselves discriminating against other women," Saini writes in her 2017 book. "Sexism isn't something that's only perpetuated by men against women. It can be woven into the fabric of a system."

Reading Saini took me back over two decades to when I was looking at Charles Darwin's papers at Cambridge University and serendipitously stumbled across three intriguing letters from the last year of the great man's life. The first of these, written on December 26, 1881, by Caroline A. Kennard, asked the scientist whether it was true that he believed in the "inferiority of women past, present and future based upon scientific principles" since he had been quoted as the authority based on whom this argument had been made "before a Company of women in Boston". Responding on January 9, 1882, Darwin wrote, "I certainly think that women though generally superior to men [in] moral qualities are inferior intellectually; & there seems to me to be a great difficulty from the laws of inheritance, ( if I understand these laws rightly) in their becoming the intellectual equals of man. On the other hand there is some reason to believe that aboriginally (& to the present day in the case of Savages) men & women were equal in this respect & this would greatly favour their recovering their equality. But to do this, as I believe, women must become as regular 'bread-winners' as are men; & we may suspect that the early education of our children, not to mention the happiness of our homes, would in this case greatly suffer." (Emphasis in original.)

Kennard responded to this at length on January 28, 1882, contending that "recent results from efforts for her higher education, in your own country and in this, are very flattering and encouraging: and are opening for women avenues for individual improvement and for the general enlightenment of her sex, and therefore, of necessity (according to the laws of heredity) for the advancement of the human race intellectually." She went on to say, "In reply to your argument that 'women must become as regular "bread-winners" as are men', have they not been and are they not largely, bread-winners, though unrecognized generally as such? Partners in business share money profits and why should not partners in marriage, where the wife, by her labor and economy does her full part toward husbanding for the future? In the unceasing demand upon the head of a household, for executive ability, fixedness of purpose, and courage of execution, are not women possessed of the same kind of qualities which would grow with the using into as apparent & grand results as are accorded to men of business, government officials, army officers, and statesmen, who all expect compensation for services rendered?" (Emphasis in original.) Kennard ended her letter with the plea "Let the 'environment' of women be similar to that of men and with his opportunities, before she be fairly judged intellectually his inferior, please -" There is no record of the ailing Darwin - he died three months later, on April 19, 1882 - having responded to this missive.

In spite of my best efforts, I found almost no information on the woman who had carried out this combative correspondence with the best-known scientist of her time. The letters told me that she lived in Brookline, Massachusetts, United States of America, and I discovered she had written a biography of Dorothea Dix, the great champion of mental healthcare in Civil War-era America, but very little else. Two decades on, the picture is vastly different. Not only is there much more information available on Caroline Kennard, but there is also the magnificent ongoing Darwin Correspondence Project where the digitized letters between Kennard and Darwin can be seen, with Kennard's elegant copperplate providing a sharp counterpoint to the ageing scientist's faint scribble. The same site also has several references and links to Kennard, her life and work, which - in turn - are put in historical/scientific context in the "Gender" section of the Correspondence Project.

The Project has also led to the publication of a recent book, Darwin and Women: A Selection of Letters, edited by Samantha Evans (Cambridge University Press), which, in the words of a reviewer, shows that Darwin "may have held less hostile views about women than previously thought".

Darwin was not quite the unrepentant male chauvinist pig some commentators have made him out to be. As he explicated in Descent of Man (1871), the "intellectual superiority" of the average man over the average woman was something that had come about, as in the case of all mammals, "partly through sexual selection, - that is, through the contest of rival males, and partly through natural selection, - that is, from success in the general struggle for life..." However, it is not as if only man's "mental powers" had developed while woman's powers had remained stagnant. Darwin contended that although natural and sexual selection had improved both men and women, since men (who are more active in the world outside the home) improved at a faster rate than women (who are less active in the outside world), in spite of continuous improvement in absolute terms, the relative difference between men and women had increased over time. What is perhaps more significant is that, unlike his contemporaries, Darwin did not believe in any kind of essential female inferiority.

The eminent French surgeon and anthropologist, Paul Broca (1824-1880), whom Darwin cited many times in Descent, had asserted in 1861, "... we must not forget that women are, on the average, a little less intelligent than men, a difference which we should not exaggerate but which is, nonetheless, real. We are therefore permitted to suppose that the relatively small size of the female brain depends in part upon her physical inferiority and in part upon her intellectual inferiority." We note how, in spite of the reasonable, "scientific" tone of Broca's prose, women's physical and mental inferiority is taken for granted.

Broca's disciple, Gustave Le Bon, put it even more directly in 1879. "In the most intelligent races, as among the Parisians, there are a large number of women whose brains are closer in size to those of gorillas than to the most developed male brains. This inferiority is so obvious that no one can contest it for a moment; only its degree is worth discussion. All psychologists who have studied the intelligence of women, as well as poets and novelists, recognize today that they represent the most inferior forms of human evolution and that they are closer to children and savages than to an adult, civilized man... Without doubt there exist some distinguished women, very superior to the average man, but they are as exceptional as the birth of any monstrosity, as, for example, of a gorilla with two heads; consequently, we may neglect them entirely."

Writing midway between Broca and Le Bon, Darwin, although asserting the present mental inferiority of women, nevertheless held out the possibility that women might become the intellectual equals of men in future. "In order that woman should reach the same standard as man," he wrote in Descent, "she ought, when nearly adult, to be trained to energy and perseverance, and to have her reason and imagination exercised to the highest point; and then she would probably transmit these qualities chiefly to her adult daughters."

Darwin did not see women as intrinsically inferior, nor did he object to actively helping increase the mental powers of women to the point where they became the equals of men. As he had written to Kennard, there were justified reasons for believing that women could "recover the equality" they had once shared with men. February 12 was Darwin's birthday. Had he been alive today, I suspect he would have been happy to see just how he is being proved right.