Humans are not interested in truth, necessarily. They are slaves of their emotions and small brain capacity when it comes to extracting structure from chaos. The search for truth is something we all thought to be natural with the sciences uncovering the secrets of this earth the past decennia. But this is only so for the tiniest percentage of our species.

Most humans don't think too much. They just live and get on with their lives. Truth is a pragmatic thing that is determined by how good it makes them feel or how it suppresses these fundamental fears which an unfriendly cosmos catapults at us. Believing that there is a god who cares is wishful thinking to which an unbelievable amount of people have succumbed. The dreadful truth about the cosmos not being necessarily good to us has not registered in the heads of the majority of the earth's population.

It could all be gone tomorrow. That's not pessimistic, it's just the logical result of observing reality. An earthquake in Haïti is incongruent with the idea of an almighty and loving God. God was made by humans for humans and this human-centric thinking might keep you asleep at night but it has nothing to do with the cold neutrality of reality.

Reality doesn't care about humans or you. You're just dust in the wind and should feel lucky to be alive. Life forms die and get born. Suffering is daily business and seems only immoral to humans but not to any other system out there (except maybe your dog). But then a religious person might object that there is no basis for morality if morality is not embedded in existence. And they have a point. Reality is not moral. Everything we consider to be moral in this universe is man-made and defined as moral because we say it is.

Morality is necessarily human-centric. We're evolving into a species which seems to start to care about the environment of human life as well. But morality still seems to consist mostly of the fear that I as an individual, my family, my country or humankind could perish at any time. We only care about these expanding circles (with myself in the center and ripples of groups I belong to as mentioned above) insofar that we can save it from harm.

But, as said before, reality doesn't care about us. Believing there is an almighty and loving God out there is denying the neutral (not evil!) environment we live in. We should become aware that we MAKE morality, we don't DISCOVER it in our surroundings.

That's why morality changes.

Morality is very biological where it addresses the further existence of our species (beginning with the circles closest to yourself seeing you'd prefer your child to live instead of a fellow countryman if you had to choose). Our biology is 'coded' (don't even think of it, you evil creationists) for survival and morality is largely defined by our DNA structure.

This sheds an interesting light on 'moral issues' such as sexuality. Sex is biology's way of guaranteeing our existence. But in recent times we've started to value procreation differently. Maybe it's our biology telling us that having descendants is not necessarily a good recipee for continuation of the species. Maybe having less kids is a reaction to the overpopulation of the world. Less is more gets a new meaning in the light of this idea.