Neanderthal Return (Paperback) (ISBN-13: 9781585002344)

Background story line is this:

A truly alien species determined that their home star would soon become a red giant and burn their home planet. They searched the Galaxy for suitable planets to relocate to. They found Earth and many other suitable planets.

Needing to learn how to 'terraform' a planet, they used Earth as the source planet in an experiment. They marked their base camp on Mars by carving a face on a mountain. They dragged a planet in to an orbit around Alpha Centauri where it receives the same amount of sunlight as Earth, salted its ocean and provided a moon for tides. They transplanted Earth life and built up ecosystems.

They finished the job by transplanting an intelligent species, Neanderthals.

The relocated Neanderthals developed civilization and modern technology. A terrible disaster left them desperate for our help.

Earth developed radio and came in loud and clear! Wars! Nuclear bombs! RACISM! The Nazi Holocaust! We frightened them. They recognized themselves in the televised pictures of Neanderthal skulls. It didn't help that our scientists characterized their ancestors as less intelligent. They TALKED about how we thought they couldn't speak!

But they need our help! They build the starship Neanderthal Return and visit the Earth Solar System.

And that's when the fun begins!