Six thousand million years of life
At what period of the earth’s history life began no one knows. But the geologists calculate the oldest rock in which any sign of living things is found must be about 6,000,000,000 years old.
The rocks that lie below these Cambrian beds contain no hint of organic matter.
In the lowest strata of the Cambrian, however, are found two small shells, one called the trilobite, the other called the lingula. That living creatures existed before these there is every reason to believe, but they left behind them no skeleton or shell.
As we get to the higher strata of the Cambrian rocks, the shells become more numerous and more varied, and, in the Ordovician, remains of sponges, corals and worms are found.
How many million years each of these ages lasted is a matter of guesswork. When the mollusks had been lying on the mud for some millions of years great sea scorpions made their appearance. They devoured mollusks and swam about among the forests of coral.
Among them a few fishes appeared — but these had no bones, only gristle. This was in the age called Silurian.
With these came certain sharks — also “gristle fishes.” They and their direct descendants lived practically unchanged for millions of years.
In the Devonian period the first true bones appeared in fishes.
As yet there had been no land. But the waters gradually sank and the dry land appeared. Soon this, too, was covered with living things. These were giant trees of which our horsetails, ferns and club mosses are the lineal descendants. Fishes discovered that they could breathe air as well as water. Presently fins gave way to flippers, and a race of gigantic newts crawled from land to water and back again in search of prey. When the trees died down they were compressed and turned to coal. The fuel we burn in our grates and stoves today is only the fossilized wood of those first forests. This is why that age is called the “Carboniferous.”
In the succeeding age, one of nature’s most extraordinary freaks appeared in the person of the nacsaurus, a huge lizard with spines as long as telegraph poles upon his back. Dragons, as we should call them today, inhabited the earth for the next few million years. Their skeletons may be seen in many museums. They lived on through the Triassic, Jurassic and Cretaceous periods.
In the Jurassic age, some of these creatures tried to fly. How they first began no one can tell, but they succeeded, and the air was alive with flying dragons.
One of these flying lizards, in the course of time, developed feathers on his wings. He is the father of all the birds.
The fierce sun warmed the cold blood of these ferocious reptiles. Thus the first mammals made their appearance — the ancestors of the elephant and rhinoceros. These came in the Eocene age.
This seems to have been the time of nature’s experiments, for few of the types that lived in those days persisted.
Soon after them came the earliest apes. A few of these were more intelligent than others and, if the Darwinians are to be believed, they came down from the trees, took stones and chopped out clubs, made themselves masters of creation and became — man.