I think we probably are predisposed to believe in magic - spiritual or supernatural things - if so, then why ? What is the purpose this predisposition? Is it a flaw of Nature ? Or do our predispositions exists for a reason ? - I think they do exist for a reason and some of these reasons may not be so mundane.
I think it is likely that our predispositions exist for the purpose of survival (as animals & spiritual creatures) and to assist us in both our physical and spiritual evolution.
A lot of the early posts are good in this thread, hard to pick just one to lead off from.
I think this one comes pretty close to how I see things. Humans have a spectrum of range of thought. Some are hamstrung by society, convention, "training/school/indoctrination," and religion - likewise these things can inform a thought as well. Seldom in my experience can a person set aside all presumptions to look at a matter with fresh eyes, typically people barge in headlong leading with their cherished presumptions.
To the OP regarding humans being predisposed to seeing/accepting "magic," I think a large part is situational, pending degree of understanding. Hard for some today probably to imagine a time when science hadn't explained away all of the mysteries of life. I still don't know what exactly thunder is...at this point I've heard 4 or 5 different "scientific" explanations, all of which disagreed with the others, at this point I just tune out. That's not even counting "angels playing ten pins."
Imagining back to a time when so much in life was a mystery, I think "magic" may have helped our forebears in some capacity, though as with so much to do with religion it also became a tool of manipulation. It wasn't unheard of for a priest to also be a magician, and magicians figure prominently throughout Classical History. I realize some may take umbrage, but I also see correlation between magicians then and scientists now, they were men of learning who could manipulate nature (maybe more accurately engineers instead of scientists), and whose methods were largely unknown to those not privy to their methods and education.
Precisely what role magicians had in regard to religion is unclear to me, but there are most certainly those who promote that position, ranging in my travels from New Age "past lives" to Moses duking it out with Pharoah's High Priests before the palace dais to Simon Magus.
I've suggested in the past a continuum from Alchemy, particularly the Taoist brand, through into modern Science in an effort to demonstrate that science has its roots in religion. This to my way of seeing things is no different, there was power to be had over those who did not know by those who did know.
I think it is also possible, though obviously unproveable in the normal sense, that some early magical science is forgotten, at least in the mainstream, though undoubtedly there are still quiet sects that keep that knowledge alive and to themselves. Given the shift in political winds centuries ago that sent many to be burned alive or worse, I can understand the trepidation. It is said Sir Isaac Newton walked a fine line between his position as a clergyman and some of the experiments he performed that in his day were accorded magical or alchemical status by some.
I still find it fascinating, the fabled Philosopher's Stone was rumored to turn base metals into gold, and impart immortality to a human. It is no surprise so many of the Courts of Europe quietly kept alchemists on the payroll - and if they didn't produce, they were easily offed with an accusation of heresy! And Ferdinand and Isabella sent so many explorers to the New World seeking...<pause for effect>...gold and the fountain of youth (immortality).
To my way of reasoning there is little difference between magic, alchemy and science, apart from the entertaining parlor tricks. It is really a matter of perspective. And let us not forget the Shamans....