Second Genesis

"Second Genesis" is a 1986 science fiction novel by Donald Moffitt.

In the previous novel, "The Genesis Quest", the alien Nar species discovered radio transmissions containing the genetic codes and cultural records of a species called Humanity, transmitted from a distant galaxy. Now the humans created with this information have discovered the biochemical key to immortality, and have decided to dedicate their now-long lives to discovering their origins in the distant Milky Way. They create a starship using a Dyson tree called "Yggdrasil", bound to a Bussard ramjet, to search for the world of their ancestors, and wind up discovering both ancient wonders and a disturbing new threat; a predatory species that cannot share the universe with anyone.