In forming a judgment on this proposition, it must be remembered that civilization covers not more than 10,000 years out of man's history of half a million or more. During 490,000 out of the 500,000 years, man was the hunter and warrior; while woman stayed at home of necessity to bear and rear the young, to skin the prey, to prepare the food and clothing. He must have a small knowledge of biology who could suppose that this long history would not lead to any differentiation of the two sexes; and the biologist knows that man and woman in some respects differ in every cell of their bodies: that, as Jacques Loeb says, "Man and woman are, physiologically, different species." But the biologist also knows that sex is a quantitative character. It is impossible to draw a sharp line and say that those on one side are in every respect men, and those on the other side in every respect women, as one might draw a line between goats and sheep. Many women have a considerable amount of "maleness"; numerous men have distinct feminine characteristics, physical and mental. There is thus an ill-defined "intermediate sex," as Edward Carpenter called it, whose size has been kept down by sexual selection; or better stated there is so much overlapping that it is a question of different averages with many individuals of each sex beyond the average of the other sex. A perusal of Havelock Ellis' book, _Man and Woman_, will leave little doubt about the fact of sex differentiation, just as it will leave little doubt that one sex is, in its way, quite as good as the other, and that to talk of one sex as being inferior is absurd. It is worth noting that the spread of feminism will reinforce the action of sexual selection in keeping down the numbers of this "intermediate sex." In the past, women who lacked femininity or maternal instinct have often married because the pressure of public opinion and economic conditions made it uncomfortable for any woman to remain unmarried. And they have had children because they could not help it, transmitting to their daughters their own lack of maternal instinct. Under the new regime a large proportion of such women do not marry, and accordingly have few if any children to inherit their defects. Hence the average level of maternal instinct of the women of America is likely steadily to rise. We conclude that any claim of biological equality of the two sexes must use the word in a figurative sense, not ignoring the differentiation of the two sexes, as extreme feminists are inclined to do. To this differentiation we shall return later.