Humans (as well as many other animals) have certain innate instincts, in other words, instincts that they have from birth, not learned ones. For a long, long time it was thought that people can be born with only really, really primal instincts such as fear of death and pain. It was hard to believe that an infant could have any instincts that are even slightly more high-level than that.
More recent studies have shown that humans do have surprisingly high-level innate instincts. For example, it has been shown that on average a very young infant is instinctively afraid of snakes, spiders and other similar animals, while at the same time not being afraid of other dangerous things. Moreover, a bit later in life many children are still afraid of snakes and spiders but not so much of other things they may already know are dangerous (such as cars or kidnappers.) Most of these children have never even seen a snake or a dangerous spider in real life.
It has become clearer and clearer that humans are born with certain higher-level survival instincts, such as fear of snakes, even though an infant cannot possibly even know what a snake is, at a conscious level.
One thing in common with these higher-level instincts is that they are always related to common dangers that humans faced a long, long time ago, never to more recent dangers. And often these fears are not even relevant today (for example the probability of an infant being harmed or killed by a snake today is next to zero.)
Evolution actually explains this perfectly. During millenia, people may be born with slightly differing, just a bit randomized, innate instincts (caused by equivalent small random changes in genes.) Some of these instincts raised the survival chances of infants in the distant past (if an infant was curious of a snake, he or she certainly had a much higher chance of being killed than if he or she was instinctively afraid of it and fled) and therefore the semi-random instincts that made infants afraid of certain things were naturally selected to stay in the gene pool.
What I'm getting at here is that some recent studies have suggested that children may also have some kind of innate belief in a creator of everything. Although one should always be wary of such studies (because children are really easily "coached" into giving the answers that the person asking them wants, even if that person isn't doing it deliberately,) it could be true.
Naturally theists have jumped onto this with full force. "Clearly" this shows that people know deep inside that God exists?
But how would this be different from all the other innate instincts that a human has? As I have commented in another blog post, belief in a higher authority may very well be a result of evolution and natural selection, as it may have helped the human species to survive because it strengthens the instinctive concepts of teamwork and the importance of being a social species where everybody cares for each other and work together for a common goal.
Such an innate belief arising from evolution is not even hard to believe. It would have to be ruled out before any supernatural causes could be even considered.