Rights come from the law of identity. Whether or not man was created by a god or is the result of eternal natural laws it does not make a difference. The founding fathers got it right when they said inalienable rights. Rights are absolutes and if men are to live together then each man must hold them as absolutes so that is why men have a right to life. All other rights come after that one or there is no point to rights.
In my opinion the founders made an error when they tied rights to a creator but it is still irrelevant because inalienable means unable to be separated from which means rights are intrinsic to man and primary to the question of who created the universe. They are what they are regardless.
There can be no unalienable set of rights without it being endowed by something outside of itself. Man can certainly come to the realization that his rights are unalienable but he must reason that this unalienability has to be endowed by something outside of mankind in order to remain unalienable by its very definition. This something, as the Founders rightly, whole-heartedly agreed with, is God.