Ultimately, the only thing that really matters is passing on ones genes. These ideas gave rise to the modern eugenics movement. The ultimate purpose for human life is to make a choice to love or reject God to determine where we will spend eternity. Jesus said that the entire law of God rests upon two commands - love God and love your fellow human. All other temporal issues are ultimately irrelevant.
Humans are a collection of chemicals fashioned and controlled by genes.
Morality is an illusion. Ultimately, the only important behavioral law is survival of the fittest. There are no hard and fast moral laws. Any behavior that fosters the survival and reproduction of the individual with the best genetic makeup is evolutionarily selected. His moral laws, like His physical laws for the universe, do not change.