CREATION BY EVOLUTION
from the summary of it presented in the history of the developing individual, and, indirectly, by comparing different animals with one another, a comparison that enables us to deduce with reasonable accuracy their family history and genealogical tree. By combining all the various lines of evidence it is possible to arrive at certain perfectly definite conclusions. In the first place, the size of animals has increased during their evolution. None of the earliest mammals were much bigger than a dog; creatures the size of a horse or a hippopotamus were unknown. The same is true of the reptiles; the giant forms appeared late in their geological history. The earliest forms of life were doubtless microscopic. Even the smallest mammal is over a million million times as large as a medium-sized amoeba.
More important than mere increase in size is increase in efficiency. No early form of life can move fast or can see or hear acutely; none has a heart or a blood-system, brain or nerves, jaws or limbs, or true head. The earliest true vertebrates have no jaws or teeth. The earliest land vertebrates could not support their bodies with their limbs. The earliest members of the horse family had limbs incapable of the speed achieved by the later horses, and the teeth of an early horse are not nearly so efficient for grinding as those of a modern horse. The brains of early mammals were barely more than half the proportional size of those of present-day mammals of the same bulk. The improvement of the efficiency of separate organs is the improvement of the tools of life; the improvement of the efficiency of the brain is the improvement of the way in which these tools can be used.
When we examine the geological history of a single group of animals, such as the mammals or the reptiles, whose past record is available to us in the fossil-bearing rocks, we find that improvement in efficiency is actually made in different
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