I think when every human realizes...

 ...that we're just the same as the cockroaches we kill or the cats we torture or the horse's leg we saw off, and that our entire lives are equally as meaningless---we might be a lot happier, or more humane. ("Humane" is the wrong word, indicating "humans." What's the word for all of life?)

As Mars dried up, we might've come from there. Or we might be a penal planet, with the worst sent here as punishment. Why else have we constantly, for the past few thousand years, been crying out for our gods/superiors? We're obviously innately missing something, have been separated from something. And multiple cultures don't just independently invent a universal source for no reason.