There has often been slipping back and degeneracy in the course of
evolution, but the big fact is that there has been progress. For
millions of years Life has been slowly creeping upwards, and if we
compare the highest animals--Birds and Mammals--with their predecessors,
we must admit that they are more controlled, more masters of their
fate, with more mentality. Evolution is on the whole _integrative_; that
is to say, it makes against instability and disorder, and towards
harmony and progress. Even in the rise of Birds and Mammals we can
discern that the evolutionary process was making towards a fuller
embodiment or expression of what Man values most--control, freedom,
understanding, and love. The advance of animal life through the ages has
been chequered, but on the whole it has been an advance towards
increasing fullness, freedom, and fitness of life. In the study of this
advance--the central fact of Organic Evolution--there is assuredly much
for Man's instruction and much for his encouragement.