There is no way to make a rational positive assertion for why humans should have inalienable rights. You have to presuppose the existence of some sense of self that transcends the individual, some universal law. If you tried to use evolution or science to do this you would either turn science into a religion or this is what would happen.
See, science was born of philosophy, so it observes a scientific praxis, and if you can’t support it rationally you can’t say it. This is called Logic. In order to do it you would have to contradict yourself and thereby falsify yourself.