Can anyone explain why, in a rapidly changing world, we need "absolute" and "eternal" morality?

IMHO, better question would be: how can dumb, unambitious and completely ordinary person help the world?

Imagine average person, with average intelligence (this means, by standards of this site, dumber then bag of hammers) and average ability, willpower and dedication. Someone who will not sacrifice or unnecessarily endanger his life, someone who will not spend the rest of his life in Africa helping the lepers, someone who will not live on bread and water to give everything to worthy cause, someone who will not give up even six pack of beer and bag of donuts to save life of starving African child :-(

But nevertheless someone who wants to make the world a better place. Any ideas?

On Marginal Revolution there was, about a year ago, similar discussion

Lots of concrete ideas, some of them even practical...