He also says: "If we go back to the genesis of the human type from some lower type of primates, we see that while the little toe has ceased to be of any use for climbing purposes, it has not come into any considerable use for walking or running. It is manifest that the great toes have been immensely developed since there took place the change from arboreal to terrestrial habits. A study of the mechanism of walking shows why this has happened. Stability requires that the line of direction--the vertical line, let fall from the center of gravity--shall fall within the base, and the walking shall be brought at each step within the area of support, or so near that any tendency to fall may be checked at the next step. A necessary result is that _if_ at each step the chief stress of support is thrown on the outer side of the foot, the body must be swayed so that the line of direction may fall within the outside of the foot, or close to it; and when the next step is taken it must be similarly swayed in an opposite direction, so that the outer side of the foot may bear the weight. That is to say, the body must oscillate from side to side, or waddle. The movement of the duck when walking shows what happens when the points of support are far apart. This kind of movement conflicts with efficient locomotion. There is a waste of muscular energy in making these lateral movements, and they are at variance with the forward movement. We may infer, then, that the developing man profited by throwing the stress as much as possible on the inner side of the feet, and was especially led to do this when going fast, which enabled him to abridge the oscillations, as indeed we see it now in the drunken man. Then there was thrown a continually increasing stress upon the inner digits as they progressively developed from the efforts of use, until now the inner digits, so large compared with the outer, bear the greater part of the weight, and being relatively near one another render needless any swaying of the body from side to side in walking. But what has meanwhile happened to the outer digits? Evidently as fast as the great toes have come more and more into play and the small ones have gone more and more out of play, dwindling for--how long shall we say?--perhaps 100,000 years." In other and simpler words, the great toe of man has wonderfully developed since he began to walk upright. This has been from greater use, and the transmission of the effects of this use to offspring. The small toe has decreased in size proportionately. This we can reasonably infer has been the result of disuse, the effects of which were also transmitted to offspring.