Beyond this, also, we have reason for believing that factors of a still more fundamentally biological character, to some extent deeper even than all these psychic elements, enter into the problem of sexual selection. Certain individuals, apart altogether from the question of whether they are either ideally or practically the most fit mates, display a greater energy and achieve a greater success than others in securing partners. These individuals possess a greater constitutional vigor, physical or mental, which conduces to their success in practical affairs generally, and probably also heightens their specifically philogamic activities.
Thus, the problem of human sexual selection is in the highest degree complicated. When we gather together such scanty data of precise nature as are at present available, we realize that, while generally according with the results which the evidence not of a quantitative nature would lead us to accept, their precise significance is not at present altogether clear. It would appear on the whole that in choosing a mate we tend to seek parity of racial and individual characters together with disparity of secondary sexual characters. But we need a much larger number of groups of evidence of varying character and obtained under varying conditions. Such evidence will doubtless accumulate now that its nature is becoming defined and the need for it recognized. In the meanwhile we are, at all events, in a position to assert, even with the evidence before us, that now that the real meaning of sexual selection is becoming clear its efficacy in human evolution can no longer be questioned.