Childrens Illustrated Encyclopedia

423

PREHISTORIC LIFE

66 million years ago

Trees with blossoms, such as the magnolia, began to

appear on earth more than 100 million years ago.

later, about 66 million years ago, dinosaurs and

many other living things became extinct (died out).

During the next few million years different kinds of

mammals and birds became more common.

150 million years ago

Dinosaurs ruled the land. reptiles such as plesiosaurs

ruled the seas, and other reptiles, the pterosaurs, flew in

the air. There were also birds and mammals at this time.

ammonites were common in the seas.

greaT ice age

about two million years ago

several ice ages gripped

earth, with warmer stretches

between. Humans evolved—

probably in africa—and

spread around the world.

in the north, they hunted

woolly mammoths, woolly

rhinos, and saber-toothed

cats. about 18,000 years ago,

ice sheets covered much of

northern europe, northern

Britain, and north america.

300 million years ago

The first amphibians had crawled out from the

water about 50 million years earlier. gradually,

they developed stronger limbs and thicker skins,

so they could live on land. They still had

to return to the water to lay their eggs.

giant ferns and horsetails grew

in the warm swamps.

Extinction

There is concern over the fact that many animals and

plants are in danger of dying out, or becoming extinct.

But ever since life began, animals and plants have died

out, to be replaced by others. This process is part of

nature. as the conditions on earth change, some

living things cannot adapt; they eventually become

extinct. scientists believe that 99 percent of all the

different plants and animals that ever lived have

died out naturally. in prehistoric times, there

were mass extinctions when hundreds of

different things died out together. These

extinctions were often due to dramatic

changes in climate. about 225 million

years ago 90 percent of all the living

things in the sea died out. Today,

animals and plants are dying out

more quickly because humans

damage and destroy the areas

where they live.

Insects such as the

dragonfly evolved

about 350 million

years ago.

Saber-toothed cats

existed 19 to 2 million years

ago. Their huge teeth enabled

them to attack and kill large prey.

The first bats

existed about

50 million

years ago.

Mosasaur was

one of the first

sea reptiles. Its

sharp teeth

show that it was a

meat eater, and it

probably hunted fish.

Find out more

coal

Dinosaurs

evolution

Fossils

Prehistoric peoples

StegoSauruS

This dinosaur lived about 150 million

years ago in north america. it became

extinct about 140 million years ago.

neanDerTHal PeoPle

These people lived from

about 120,000–35,000 years

ago. They were smaller than

humans and are now thought

not to be ancestral to them.

it is debated, however,

whether they interbred

with humans.

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