By each new variation the existing relation between organism and environment is disturbed. The variation may, however, prove its utility at once by a more exact correspondence than before with the requirements of external conditions. But, in what are called the higher grades of life, variations from the type are sometimes not immediately useful, although they may ultimately become most advantageous.[229] Were it not for the remarkable power of persistence possessed by the higher animals, the modified organism would be unable to hold its own. The great majority of such eccentric or extraordinary variations do, as a matter of fact, soon disappear, because unable to prove their utility. But others of them, either by the power they give the organism to mould circumstances to itself, or by their appropriateness to the greater complexity which comes with the increased number of living organisms, and the more delicate readjustment it requires, prove themselves to be fitter to live than if no variation had taken place and the preceding state of relative equilibrium had been maintained. The higher adjustment of life to its surroundings, which marks each stage of advancing evolution, had its beginning in the rupture of the original simpler harmony that previously existed. [Sidenote: especially in human conduct.] If we compare human conduct with that of animals lower in the organic scale, it becomes evident that there is a broad difference between the two in this, that actions in the former are purposed, performed with a definite end in view; whereas, in the latter, they seem to be the blind result of impulse, and there are slight, if any, traces of purpose. In activity of the latter kind, natural selection works in the ordinary way by choosing for survival the animals which behave so as best to suit their environment. But actions done with a view to an end may anticipate the verdict of this natural law. The agent may see that conduct of a particular kind would conduce to the promotion of life, while conduct of a different kind would render him less fit to live; and, as a consequence, the former action may be chosen. In this way development may be anticipated, and the present order of affairs may be disturbed, more or less forcibly, in order to bring about a foreseen better state of things.