Another of the more important lessons to be learnt from the pages of this book of life's history is the conservative influence of the law of inherited nature; a law which makes for the preservation of racial types by suppressing wide deviations from the normal. A familiar illustration of this may be found in the fact that the children of parents of great height or of very short stature usually revert to the average of the race. The significance of this genetic relation in maintaining an efficient people was unrecognised until quite recent times, and though valuable evidence is accumulating on the descent of hereditary character in mankind, no definite conclusions have yet been reached on the _intensity_ of the transmission of qualities. It is, of course, a subject of intense complexity, the full discussion of which is here impossible. In the interests of future generations it is, however, to be wished that more thought were given to the conclusions it is allowable to draw. "If," for instance, says a recent writer, "instead of allowing the race to mate at random we selected both parents for some one quality, we could raise the intensity of inheritance and establish gradually, by continued selection, a strain in which the quality reached a value much higher than the average in the original mixed race...."[99] Thus could a race be strengthened for life's calls, or, on the contrary, until and unless the people are awakened to the existence and bearing on their national security of such fundamental hygienic influences, it can be emasculated. No such selection is likely ever to dominate human marriages, but an appreciation of these and similar facts is fundamental to national progress; and in time the dissemination of such knowledge will be considered a parental duty, the more urgent since the resources of civilisation and ill-regulated sympathy have combined to brush aside the sterner laws of nature, so that the deteriorated threaten to become the chief progenitors of the next generation.