Genesis — Poul Anderson

Artificial intelligence has been developed to a point where human intelligence can be uploaded into a computer, achieving a sort of hybrid immortality. Astronaut Christian Brannock welcomes this technology, technology that will make it possible for him to achieve his dream and explore the stars.

A billion years later, Brannock is dispatched to Earth to check on some strange anomalies. While there, he meets Laurinda Ashcroft, another hybrid upload. Brannock and Laurinda join forces and investigate Gaia, the supermind dominating the planet, and learn the truth of her terrifying, secret plans for Earth.