The Many-Colored Land

Description for THE MANY-COLORED LAND by Julian May:

FLIGHT INTO THE UNKNOWN

An orderly and peaceful interstellar society, the twenty-first century's Galactic Milieu had little place for the incurable adventurer, the secret psychotic, or the ruthless con man.

So, when a one-way time tunnel to Earth, six million B.C., was discovered, every misfit for light-years around hurried to pass through it, hungry for adventure, the romance of the unknown, and a life free of the Milieu's stuffy rules.

Each sought his own brand of happiness But none could have guessed what awaited them. Not even in a million years...

This is #1 in The Saga Of Pliocene Exile.