Shores and Islands Th 
tiles, the age of dinosaurs. Toward the end of this era certain 
archaic mammals made their appearance; the era ends with 
a period of world-wide mountain building. 
Cenozoic Era | 
(began about 40 million years ago) 
Now the archaic mammals began to disappear. Dinosaurs 
were extinct. The higher mammals began to appear about 
twenty million years ago. The Pleistocene Epoch began about 
one million years ago, an epoch of successive glaciations and 
interglacial intervals. The elephant and mastodon, the saber 
tooth tiger, the giant ground sloth, the horse make their ap- 
pearance; some die out. The progenitors of man put in their 
bid in the struggle for existence. The last epoch, the Recent, 
_ began fifteen to twenty-five thousand years ago. It may be 
merely an interglacial epoch. 
THE FUTURE 
It may not be out of place at this point to say a few words 
about the future. Barring some catastrophic occurrence like 
an explosion of the sun, which would certainly spell doom 
for all the earth’s inhabitants, there is no reason to suspect 
that our planet might not endure another thousand million 
years, with constantly changing climatic conditions, but 
still capable of supporting life. But the prospects for man, 
the species, may not be so bright. None of the species of 
higher animals has survived for an indefinite length of time. 
The early higher animals are now all extinct. Each species, in 
its time, has fallen victim to overspecialization, a fate which 
-may equally well overwhelm the human races. 
Examples of overspecialization are the division of labor in 
modern industry and the accompanying mass unemployment 
