Second Principle of Evolution
As we have no recognisable remains of the animals and plants of
the earliest age, we will not linger over the Archaean rocks.
Starting from deep and obscure masses of volcanic matter, the
geologist, as he travels up the series of Archaean rocks, can
trace only a dim and most unsatisfactory picture of those remote
times. Between outpours of volcanic floods he finds, after a
time, traces that an ocean and rivers are wearing away the land.
He finds seams of carbon among the rocks of the second division
of the Archaean (the Keewatin), and deduces from this that a
dense sea-weed population already covered the floor of the ocean.
In the next division (the Huronian) he finds the traces of
extensive ice-action strangely lying between masses of volcanic
rock, and sees that thousands of square miles of eastern North
America were then covered with an ice-sheet. Then fresh floods of
molten matter are poured out from the depths below; then the sea
floods the land for a time; and at last it makes its final
emergence as the first definitive part of the North American
continent, to enlarge, by successive fringes, to the continent of
to-day.*
* I am quoting Professor Coleman's summary of Archaean research
in North America (Address to the Geological Section of the
British Association, 1909). Europe, as a continent, has had more
"ups and downs" than America in the course of geological time.
This meagre picture of the battle of land and sea, with
interludes of great volcanic activity and even of an ice age,
represents nearly all we know of the first half of the world's
story from geology. It is especially disappointing in regard to
the living population. The very few fossils we find in the upper
Archaean rocks are so similar to those we shall discuss in the
next chapter that we may disregard them, and the seams of
carbon-shales, iron-ore, and limestone, suggest only, at the
most, that life was already abundant. We must turn elsewhere for
some information on the origin and early development of life.
The question of the origin of life I will dismiss with a brief
account of the various speculations of recent students of
science. Broadly speaking, their views fall into three classes.
Some think that the germs of life may have come to the earth from
some other body in the universe; some think that life was evolved
out of non-living matter in the early ages of the earth, under
exceptional conditions which we do not at present know, or can
only dimly conjecture; and some think that life is being evolved
from non-life in nature to-day, and always has been so evolving.
The majority of scientific men merely assume that the earliest
living things were no exception to the general process of
evolution, but think that we have too little positive knowledge
to speculate profitably on the manner of their origin.
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