The billion-year history of
Urantia extends through five major eras: the Pre-Life era (Archeozoic),
the Life-Dawn era (Proterozoic), the Marine Life era (Paleozoic), the
Early Land-Life era (Mezozoic), and the Mammalian era (Cenozoic). At
the dawn of the marine‑life period, plants and animals were fairly
well distributed throughout the seas and vegetation had begun to move
onto the land.
Four hundred million years
ago the first multicellular animals suddenly made their appearance.
The trilobites evolved and dominated the seas for ages. Periodically,
land masses would sink into the oceans and rise again. At times the
American land mass was almost entirely submerged. Greenland was warmed
by the Gulf Stream. Sediments of conglomerates, limestone, shale, and
sandstone were deposited.
Three hundred and sixty
million years ago marine life included seaweed, sponges,
one-celled organisms, trilobites, and other crustaceans. Of the three
thousand varieties of brachiopods appearing at the close of this period,
only two hundred have survived into present times.
Three hundred and fifty
million years ago saw the beginning of great flood periods on the
continents. This age was characterized by enormous amounts of limestone
laid down by the lime-secreting algae.
Three hundred and ten million
years ago every type of marine life below the vertebrate scale was
represented. Sea worms, some types of jellyfish, corals, and sponges
evolved. Cephalopods developed and have survived as the modern pearly
nautilus, octopus, cuttlefish and squid. Shelled animals were single-shelled
and bivalve gastropods-drills, periwinkles, snails, oysters, clams and
scallops-and by valve-shelled brachiopods.
Three hundred million years
ago another great flood era occurred. The enormous deposits of animal
and vegetable matter carried down with this land submergence provided
the world with gas, oil, zinc, and lead.
Two hundred and eighty million
years ago the continents had largely re-emerged. The trilobites
declined. The cephalopods became masters of the seas; some of the larger
mollusks grew to be fifteen feet long. Coral-reef formations multiplied.
During this age the primitive water scorpions evolved and soon thereafter
the first air breathing scorpions appeared.
Two hundred and fifty million
years ago vertebrates suddenly appeared in the fish family. The
land was rapidly overrun by new orders of vegetation. Ferns appeared
suddenly and quickly spread over the face of the earth, some growing
to be one hundred feet high. Leafless trees developed. The atmosphere
of the earth became enriched with oxygen.
Two hundred and ten million
years ago warm‑water seas again covered most of North America
and Europe. Out from the warm waters came snails, scorpions, and frogs.
Spiders, cockroaches, crickets, locusts, and thirty-inch dragonflies
soon followed.
Two hundred million years
ago the most active stages of worldwide coal formation were in process.
One hundred and seventy
million years ago great evolutionary changes took place. Lands rose
and ocean beds sank. The earth's crust folded extensively, and inland
lakes and seas evaporated. Two new climatic factors appeared-glaciation
and aridity. Thousands of marine animals perished. Of the 100,000 species
of life on earth during this era, less than five hundred survived. Harsh
weather replaced the mild climate. Insects underwent radical changes
to meet the demands of winter and drought.
This period of biologic adversity
eliminated all forms of life except those which had survival value.
At the close of the marine-life era, the land was largely covered with
vegetation, and the atmosphere had become ideal for animal respiration.
The vast oceanic nursery of life on Urantia had served its purpose.