The enormous amount of time that has passed since fossils were once living creatures or
plants is so HUGE that our clocks an calendars can not measure or record it. This vast period
of time, marked by two eons of geologic time, is measured by millions of years.
The Precambrian Eon was the period that began with the birth of the solar system some 4,000
million years ago by scientist's estimates, and lasted until 600 million years ago.
Then the earth entered the Phaneozoic Eon about 600 million years ago, which was the
Cambrian period and opened with the Paleozoic Era. In the Paleozoic the first multi- celled,
hard bodied life appeared, and the beginning of the fossil record was opened. After a huge mass
extinction where 95% of the life on earth became extinct, the Mesozoic Era began. The Mesozoic
era ended with the extinction of the dinosaurs about 65 million years ago.
But the fossil record continues to much closer to our time. Following the end of the
Mesozoic we entered into what scientists call the Cenozoic, and here was when more recent
fossils were formed. After the Age of the Dinosaurs, came the age of the prehistoric mammals
like the saber tooth tiger and the giant Columbian Mammoths that roamed North America. Fossils
from the Miocene, Pleistocene and Holocene that went to about 100,000 years ago have been
discovered in California. The Mammoths discovered out on the Channel Islands for example lived
to just 11,000 years ago ( right about the time the first humans began showing up in California
and out on the islands ). While we may think 11,000 years was a long time ago, the fossil record
reveals that those mammoths lived in relatively recent time.