Time Immemorial

They said that time travel was risky but it had been done before.
They said that there was no risk of paradox.
They said history couldn’t be changed.
They said the past, present, and future were safe.

They were wrong.

Now the survivors of a doomed expedition through time must find a way to survive in a world 370,000 years ago they know nothing of. A world that shouldn’t exist. But the question remains: who changed history? And why?