http://www.clarku.edu/students/philo...docs/nagel.pdf if you haven't yet- Nagel's argument is quite relevant here.
If the Berkley guide to evolution did not make this clear to you, try this book:
Amazon.com: Darwin's Dangerous Idea: Evolution and the Meanings of Life: Daniel C. Dennett: Books
I'm still pretty convinced that you don't understand how evolution works, so try reading some of this stuff. To me, evolution is a big reason why ethics cannot be approached from a foundational perspective like you try to. Understanding this critique in depth (which Dennett makes much better than I ever could) will either give you more convincing reasons for your understanding of ethics or will show you your error- either way you can only benefit.