Atheism and/or agnosticism is a natural stance

I begin by thanking my opponent for what is sure to be an interesting discussion. In the interest of full disclosure, I am an atheist and shall argue that theism is the natural stance that human beings take when confronted with the sheer complexity of existence. However, as someone suggested previously, we should make clear what we mean by "natural". I believe what we are referring to as "natural" in this case is that which arises solely out of the natural functioning of the human mind. The human mind, being the product of evolution, is a natural entity, and anything it produces will be produced, in this sense, "naturally". To put a cap on this explanation, if we were to leave a human being in nature, without contact with any other human beings whatsoever, what would he or she conclude about the world? My thinking is that this Crusoe would resort to theism in his or her explanation of the world and life. My opponent seems to think this Crusoe would resort to either agnosticism or even atheism. I shall support my position with a priori support from evolutionary thinking and a posteriori evidence from science. An article by Michael Shermer in June 2009's Scientific American has relevance to this discussion. He wonders why people believe in conspiracies, aliens, gods, and souls. He identifies the answer as "patternicity". By "patternicity", he refers to the natural human tendency to identify patterns out of noise. While some of these patterns are real and useful (e.g. changes in weather), others are not (e.g. the face on Mars). A lack of a "baloney-detection device" is due to natural selection for minds that commit less type-I errors (false positive; e.g. thinking the bush rustling is a predator instead of the wind) than type-II errors (false negative; e.g. thinking the bush rustling is the wind instead of a predator). The cost of committing a type-I error is less than the cost of making a type-II error. With a more developed mind, this natural, evolutionary growth leads us to make type-I errors about larger, more abstract aspects of existence, producing religion and theism(1). Neuroscience also explains how humans "find patterns and impart agency to them" (Hood's SuperSense, 2009). For example, children naturally think the sun has intentioned mental states, which is why they put smiley faces on the sun in drawings. According to Hood, "Many highly educated and intelligent individuals experience a powerful sense that there are patterns, forces, energies, and entities operating in the world. More important, such experiences are not substantiated by a body of reliable evidence, which is why they are supernatural and unscientific. The inclination or sense that they may be real is our supersense." Shermer concludes, "We are natural-born supernaturalists"(1). The a posteriori evidence in favor of my position deals with the face that religious beliefs are found in all human groups, going back to the beginnings of human culture. This undoubtedly makes theism a natural part of human life and civilization(2). Advances have been made in empirically explaining the mental machinery behind religious belief. According to Pascal Boyer, there is no "religious module" in the brain. Religious thought contains a variety of systems. No one of these parts is special, but belief in religion activates mental machinery involved in a wide spectrum of non-religious functions(2). This explains why religion is so widespread throughout human cultures, even without adequate social contact to transmit the idea of theism. Having identified the human mind as a natural entity, it follows deductively that the "natural stance" or nature human response to existence on Earth is some sort of supernaturalistic worldview (i.e. theism). I conclude by quoting Voltaire: "If God did not exist, it would be necessary to invent him"(3). *Sources in Comments section.