James,
A pre-disposition is not a pre-destination. Believing is ultimately a choice, even for those predisposed towards religion. The science suggests a strong correlation between intelligence, education and a rational personality and secularism/atheism, just as the tendencies for those with a less rational personality, less intelligence and less education show a strong correlation towards religiosity.
Lots of empirical data support this, but a strong correlation is not a direct, cause and effect, correlation. With more education, including a more wordily, sophisticated experience, religion can wane even amongst those more typically disposed to it.
Nature/nurture is of course alive and well; no one disputes that, and Cofty's OP doesn't suggest that.
To me, the nature/nurture issue isn't what this OP is about; it is about how we evolved as a species to have a high disposition towards religiosity. That is interesting. Examining the difficulties of the species to survive is where it all starts. Maslow's hierarchy suggests that, when all of your time is spent looking for food and fending off threats (security), there isn't much time for more highly evolved pursuits. Throw in thousands of years of superstition and irrational fear of a god killing you on the spot for something you did, killing your child for something you did, making your crops fail or the rain to go away because of something you did, that you will be punished after death with fire, purgatory, eternal destruction or being re-incarnated as a worm for something you did, and Cofty's OP makes a lot more sense.
Our DNA looks like it does for a reason. And, when you consider that religion has, for thousands of years, discouraged research, rational analysis and academic achievement, dear god there is no wonder we bred a predisposition into our DNA for religiosity. For many religions and for thousands of years, only the hierarchy (hieroglyphics) and the religious elite were educated or even allowed to be educated.
Absent these external, social and cultural forces, our species should begin to evolve away from it. And it is, predictably. Thank god (I'm an atheist so this is simply a phrase to me).
Even today, one of the first things that the high control religions do when they take over is to kill the academics and the rational/secular, or attempt to silence them.