There is a tendency in the mid of the layman to think of the divisions of geological time as being sharp ad definite lines. We are to remember that the scientist’s classification of the epochs and eras of the past are to the highest degree arbitrary; the changes that took place were rather tendencies than abrupt departures from an established order.

The Pliocene differed from its preceding age in having a slightly lower temperature, reaching in Idaho a climate similar to the present one, and having in consequence flora and fauna not unlike those with which we of today are familiar. It is in the strata formed in the latter part of this long period that we find the first evidences of mammalian life in Idaho.

The great lake formed by the lava flows that reached up the mountainsides bordering the ancient Snake, is known to science as “Payette Lake”. In the Pliocene sediments left by this old fresh-water sea we find fossilized pieces of driftwood, worn smooth by the waves and surfs of thousands of years ago. Down to the beaches of this ancient lake came herds of camels of a dozen different varieties and sizes; under the trees an uncouth ground-sloth made its slow and awkward way.

The fossilized bones of these humble creatures from the oldest page in the history of mammalian land-life in the Idaho country.

What we may discover in the future cannot be predicted; the surface of Idaho has been barely scratched.

Fossils on the Old Oregon Trail In 1929 the Smithsonian Institution began excavation of beds of fossils on the south bank of the Snake River, directly across from the town of Hagerman, in Gooding County. The results were of sufficient interest to justify continuance of the work during succeeding years.

The deposits are situated in the end of a short spur-hill over looking the river, some fifty feet below the top of the plain of which the hill is a part. The bones of a species of horse, several kinds of rats, a large cat, two varieties of camels, ground-sloth, a large beaver, an otter, sort of wild hog, swamp-turtles, a frog, and a mastodon have been found in the Hagerman valley.

Up to the present time we have no evidence whatever of any human life in Idaho prior to the comparatively recent date of the advent of the American Indian.


Sources:
"Idaho: The Place and Its People" by Bryon Defenbach
"History of Idaho" by James H. Hawley