Page:Popular Science Monthly Volume 10.djvu/207

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AMERICAN ZOÖLOGISTS AND EVOLUTION.

tition, embracing large cutting tusks, and altogether forming a beast like the fabled monsters of old.

A study of its cranial cavity, made by Prof. Marsh, shows that its brain was proportionally smaller than that of any known mammal. Indeed, it was almost reptilian, and of such diminutive size that it could have been drawn through the neural canal of all the presacral vertebræ. Prof. Marsh has followed up this discovery with the most important results, and is now prepared to state the following conclusions:

1. That all the Tertiary mammals had small brains.
2. There is an increase in the size of the brain during this period.
3. This increase was mainly confined to the cerebral hemispheres or higher portion of the brain.
4. In some groups the convolutions of the brain have gradually become more complicated.
5. In some the cerebellum and olfactory lobes have even diminished in size.

He also finds some evidence that the same general law holds good for birds and reptiles from the Cretaceous to the present time.[1]

Thus we have in other groups as well as man convincing proof that, with successive survival of forms, there is a corresponding survival of larger brains.

Prof. Shaler[2] has offered some suggestive thoughts in showing the intense selective action which must have taken place in the shape and character of the pelvis in man, on his assumption of the erect position—the caudal vertebræ turning inward; the lower portion of the pelvis drawing together to hold the viscera, which had before rested on the elastic abdominal walls; the attending difficulties of parturition, and other troubles in those parts—all pointing to the change which has taken place.

In this connection Prof. Shaler remarks that the question of labor in woman must not be overlooked from this standpoint.

In a memoir on the shell-heaps of Florida, by Prof. Wyman, wherein he describes a number of low characters in man already alluded to, he gives the following conclusions: "The steady progress of discovery justifies the inference that man in the earlier periods of his existence, of which we have any knowledge, was at most a savage, enjoying the advantage of a few rude inventions. According to the theory of evolution, which has the merit of being based upon, and not inconsistent with, the observed analogies and processes of Nature, he must have gone through a period, when he was passing out of the animal into the human state, when he was not yet provided with tools of any sort, and when he lived the life of a brute.[3]

  1. American Journal of Science, vol. xii., July, 1876.
  2. "Proceedings of the Boston Society of Natural History," vol. xv., p. 188.
  3. "Memoirs of the Peabody Academy of Sciences," vol. i., part iv.