you're asking two different questions here (maybe).
1) is the organized religion Christianity natural?
2) is religion (itself) natural?
to the first i'd say definitely no. Christianity is a contingent phenomenon that exists because of a bunch of historical happenstances that created the right atmosphere for a religion like Christianity to begin and flourish.
to the second i'd ask if you meant "religion" in the sense of different organized religions or if you meant "religious thought".
if you mean religion in the first sense then i'm sure you can see that my answer would be the same as it was when you asked specifically about Christianity. because if you mean religion in the sense of organized religions then that's just the general heading for all the religions that each began and flourished because of the contingent historical factors.
but if you mean is religious thought natural then me answer is an emphatic yes. the results of all kinds of research in neuro-psychology and cognition show that this is so. it's hard to explain in this space but it has to do with agency detection and Theory of Mind and other cognitive systems that short circuit leading us to see agency and attribute minds when there is none. as J. Anderson Thomson has said, it's just as natural as eating junk food is. we eat junk food because we evolved to crave sweet fatty high calorie foods when those foods were scarce and it made sense for our minds to drive us to eat as much of those foods as often as we could. and it doesn't matter that now we're no longer in an environment where those foods are scarce. behaviors we evolved over millions of years aren't countered by 10,000 years of modern (evolutionarily speaking) living.
and the same is true with religious thought. we evolved to have an overactive agency detection system because being able to spot and track other agents increases survival. and having an overactive agency detection system means you're more likely to spot agents. and if you mistake something for an agent sometimes because your agent detector is overactive it's no big deal really because the alternative- not spotting an agent when it IS an agent- could get you killed. as has been said, seeing a tiger in the grass when it's not a tiger won't hurt you, but ignoring the "shadow" in the grass when it IS a tiger will get you eaten.
and we evolved to have a Theory of Mind because once you spot an agent the natural thing to do is to attempt to guess at what that agent's goals and desires are. but if it has goals and desires then it has a mind.
so thunderstorms [or anything else] seem to be agents. and if it's an agent then it has a mind with beliefs and desires and goals about things.
so, it's a misfiring of evolved features of our brains. but an entirely natural misfiring.
Justin L Barrett- Why Would Anyone Believe in God?
Pascal Boyer- Religion Explained
Scott Atran- In Gods We Trust
Todd Tremlin- Minds and Gods
J. Anderson Thomson- Why We Believe in God(s) [forthcoming]
here's a video of Thomson explaining a little of the particulars:
I read somewhere years ago that RELIGION and PATRIOTISM are part parcel of this same survival mechanism.
Maybe there is hope we can evolve beyond these destructive traits.
yeah, totally agree with that. it's done so often there's even a name for it- the naturalistic fallacy.
plenty of things are good that aren't natural. plenty of things that are natural aren't good.
The first humans did not worship a god of any kind. Animism was the religion of hunters and gatherers, that, and they worshiped their ancestors who passed on information of food and water sources. Their religion was completely naturalistic. When we moved to horticultural societies there were beliefs in ghosts of ancestors, but again, there was no real god or god-like figure.
I would contend that religion in general is based on fear. In early Hindu societies, the entire social structure was based on the caste system ruled by Brahmans, or priests. They shaped the entire society and all of its social relationships. People followed the rules of their caste because they believed they would move up the social ladder in the next life. If they disobeyed the priests, they could move down. Of course we know how fear plays a role in Christianity. I get the "what if you're wrong" question quite often...
I think it is natural for humans to be curious, ask questions, and seek information. For most people, Christianity answers questions of how they were created, how they are to live, and what is going to happen to them when they die. Having answers to these questions takes away those fears. Is it natural? No. The only natural elements are the curiosity and the fear. The rest is a brilliant hoax.