There's this book I read about eight years ago. It a paperback, in English, and didn't seem very old at the time.
It's about two hybrids, both humanoid but combined with animals. The guy only has an animal hand that makes him different if I recall. The girl looks fully human. Earth lacks new human genetic material as they've cloned themselves for too many millennia. There were Explorers who were sent out to furthest reaches of the Galaxy and now they must return to replenish the earth. Many of these hybrids are sent out and they find these evolved humans. Some are too far evolved that they no longer resemble humans even genetically, some are more plant that human, etc.
I'd like to know what the book's name is. I hope it's not too little information