Page 19 - 443
P. 19
IT IS INTERESTING TO KNOW
How Long Has There Been Life on Earth?
The earth is about 41/z billion
years old, but life did not exist
on this planet until about 2
billion years ago, when certain
kinds of bacteria and algae
began to appear. Land plants
did not appear until about 430
million years ago; reptiles, 300
million years ago; and modern
mammals, 75 million years
ago. The first apes appeared
about 35 million years ago, and
the first apelike men, about 10
million years ago. Man,
himself, has been on earth for
only about 300,000 years.
Can you imagine...
If the 41/2-billion-year
history of the earth were to
be measured in proportion to
one year, man would not
appear until Dec. 31, at 8:30
in the evening!
17
