Life is our fundamental value. There is nothing higher. When life ends, our neural circuitry shuts down, we are no more. We, the human exist as a concept driven identity within a living animal. When the animal dies, well we die also. There is nothing to carry on; no afterlife, no god, nothing. The light goes out, not elsewhere. That make life it's self the most important thing in our life. End of story.
We should not do anything that detracts, reduces, endangers, degrades, confuses life, we should do all that improves it. Religions do not address reality; they are waste of time. Ethics has value, as it sorts out some of the marginal things that could damage life quickly or slowly.
Ethics, in reality do not need any attachment to religions, although they traditionally have been. It is easier to use tradition and mystic pronouncement rather than logic. That is not to say these are wrong, but logic is the ultimate test of rightness. It it is not logical, then, it is not right. But that depends on the basis of ethics. Life, political equality, individual rights, property rights, self control, freedom. Those are the foundations. All else can be derived from those foundations. Well maybe, there may be more as well.