THE BEGINNING OF LIFE
There is, perhaps, no other chapter in the chronicle of the earth
that we approach with so lively an interest as the chapter which
should record the first appearance of life. Unfortunately, as far
as the authentic memorials of the past go, no other chapter is so
impenetrably obscure as this. The reason is simple. It is a
familiar saying that life has written its own record, the
long-drawn record of its dynasties and its deaths, in the rocks.
But there were millions of years during which life had not yet
learned to write its record, and further millions of years the
record of which has been irremediably destroyed. The first volume
of the geological chronicle of the earth is the mass of the
Archaean (or "primitive") rocks. What the actual magnitude of
that volume, and the span of time it covers, may be, no geologist
can say. The Archaean rocks still solidly underlie the lowest
depth he has ever reached. It is computed, however, that these
rocks, as far as they are known to us, have a total depth of
nearly ten miles, and seem therefore to represent at least half
the story of the earth from the time when it rounded into a
globe, or cooled sufficiently to endure the presence of oceans.
Yet all that we read of the earth's story during those many
millions of years could be told in a page or two. That section of
geology is still in its infancy, it is true. A day may come when
science will decipher a long and instructive narrative in the
masses of quartz and gneiss, and the layers of various kinds,
which it calls the Archaean rocks. But we may say with confidence
that it will not discover in them more than a few stray syllables
of the earlier part, and none whatever of the earliest part, of
the epic of living nature. A few fossilised remains of somewhat
advanced organisms, such as shell-fish and worms, are found in
the higher and later rocks of the series, and more of the same
comparatively high types will probably appear. In the earlier
strata, representing an earlier stage of life, we find only thick
seams of black shale, limestone, and ironstone, in which we seem
to see the ashes of primitive organisms, cremated in the
appalling fires of the volcanic age, or crushed out of
recognition by the superimposed masses. Even if some wizardry of
science were ever to restore the forms that have been reduced to
ashes in this Archaean crematorium, it would be found that they
are more or less advanced forms, far above the original level of
life. No trace will ever be found in the rocks of the first few
million years in the calendar of life.
The word impossible or unknowable is not lightly uttered in
science to-day, but there is a very plain reason for admitting it
here. The earliest living things were at least as primitive of
nature as the lowest animals and plants we know to-day, and
these, up to a fair level of organisation, are so soft of texture
that, when they die, they leave no remains which may one day be
turned into fossils. Some of them, indeed, form tiny shells of
flint or lime, or, like the corals, make for themselves a solid
bed; but this is a relatively late and higher stage of
development. Many thousands of species of animals and plants lie
below that level. We are therefore forced to conclude, from the
aspect of living nature to-day, that for ages the early organisms
had no hard and preservable parts. In thus declaring the
impotence of geology, however, we are at the same time
introducing another science, biology, which can throw appreciable
light on the evolution of life. Let us first see what geology
tells us about the infancy of the earth.
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