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It is important to notice that this great uprise of the land and the series of disturbances it entails differ from those which we summed up in the phrase Permian Revolution. The differences may help us to understand some of the changes in the living population. The chief difference is that the disturbances are more local, and not nearly simultaneous.
Here, in Carboniferous times, grew the gigantic fern-like trees, the Sigillaria and Lepidodendron, whose petrified trunks, for aeons buried beneath the deposit of the Permian seas, and then, during other aeons, slowly uncovered by the gentle action of the eroding rains, we saw scattered on the ground.
Comparing the amount of the differences between them and modern lizards, with the prodigious lapse of time between the Permian epoch and the present day, it may be said that the amount of change is insignificant. But, when we carry our researches farther back in time, we find no trace of lizards, nor of any true reptile whatever, in the whole mass of formations beneath the Permian.
It is a remnant of the Permian sandstone that once covered the whole Grand Canyon region, and its brilliant red, when illuminated by the vivid Arizona sun, explains why for so many years it has been a prominent landmark of the plateau.
It characterises the earlier periods of the earth's history, whereas in the secondary strata, or those newer than the Permian, the homocercal tail predominates.
Probably they had been developed during the later Carboniferous, since we find them already branched into three orders, with many sub-orders, in the Permian. The stimulating and selecting disturbances which culminated in the Permian revolution had begun in the Carboniferous. Their origin is not clear, as the intermediate forms between them and the amphibia are not found.
How much later, it is not so easy to declare, although probably they are not newer than the beginning of the Permian period, as no tin lodes have been discovered in any red sandstone which overlies the coal in the south-west of England. There are lead veins in Glamorganshire which enter the lias, and others near Frome, in Somersetshire, which have been traced into the Inferior Oolite.
Of the insects and their fortunes in the great famine we have no direct knowledge; no insect remains have yet been found in Permian rocks. We shall, however, find them much advanced in the next period, and must conclude that the selection acted very effectively among their thousand Carboniferous species. The most interesting outcome of the new conditions is the rise and spread of the reptiles.
Archibald Geikie in Ayrshire have shown that some of the volcanic rocks in that county are of Permian age, and it appears highly probable that the uppermost portion of Arthur's Seat in the suburbs of Edinburgh marks the site of an eruption of the same era. Two classes of contemporaneous trap-rocks occur in the coal-field of the Forth, in Scotland.
The Permian revolution, to which the Pleistocene Ice-Age comes nearest in importance, wrought such devastation that the overwhelming majority of living things perished. Do we find a similar destruction of life, and selection of higher types, after the Pleistocene perturbation? In particular, had it any appreciable effect upon the human species?
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