~45,000 years ago - An ape develops a sense of self, an ego, and is the first to feel bad about himself.
~40,000 years ago - As this turns out to be maladaptive, apes develop the ability to pretend these negative feelings about the self are really the fault of another ape. Later apes would call this "projection."
~35,000 years ago - Apes find they need to work together to survive the encroaching ice age. Blaming other apes becomes maladaptive. But "blame", a concept previously foreign to nature, has become such a part of ape culture and species survival that they must invent an external being to blame. Thus the first god is invented, and simultaneously the first demon.
~30,000 years ago - Apes have now become so accustomed to external attribution for the things that happen around them (the majority of which they see as bad), they begin to forget how to take both credit and responsibility for the things happening around them. They begin thanking anything and everything for successes great and small. They thank rocks, trees, water, and especially the giant thermonuclear fusion reactor their planet happens to orbit. They thank everyone but one another, because blame is now so deeply entrenched that it colors everything they see. Atheism begins its long slumber.
~10,000 years ago - The apes begin to flourish as the ice age recedes. No longer huddled in caves, they create farms and cities. They mingle freely with other apes, who they eagerly begin to blame as in their celebration, they are so eager to praise nature that they cannot reconcile to blame it as well. Deities are now more of a cause for celebration than condemnation, so their many blames must fall on the shoulders of their fellows. "Hell," as one later ape would put it, "is other apes." Ape war flourishes, to the point that it gets its own gods among most every tribe. Most of them are forgotten, since their followers were wiped out by the very wars they celebrated. And despite their followers' insistence in their existence, none have come back to say "hi" since.
~7,500 years ago - Apes realize they can use war to change the god other people believe in, if they kill the devout and threaten those unsure. Atheists go into hiding (those that survived).
~2,000 years ago - An ape comes along who says that while the blame structure is all well and good, the main point of having one is not to kill each other but to make it easier for apes to work together. Many apes, especially those with power over other apes, see this as an affront and nail his limbs to a tree. Certain apes take this as a sign that he was a god-made-ape, and they later decide they must kill anyone who does not believe he was such, completely missing the whole point.
~1,000 years ago - Atheism begins to stir, and debate begins sporadically as to whether it is really necessary to blame and praise the chaotic laws of nature for every single thing that happens, for better or worse, while attributing these actions to some plan which is incomprehensible (yet surely for the ultimate good) to apes. Theists, for the most part, enter the debate sanguinely, sure in their blame structure's validity. Other apes, however, especially those whose power over their fellows depends on their status as mouthpiece for a deity and designator of blame, enter in to the debate more violently. Hence the "sporadically" in the first sentence.
~250 years ago - Apes seeking freedom from other people's gods start to chafe at the rule of apes from across the sea. They eventually found a country based on the freedom to designate one's own blame structure. The freedom from having a blame structure is not rigidly coded into the new ape law. The general consensus among the founding apes in this new ape land is that there can be no "official" blame structure, but they do not go so far as to abandon blame. They also recommend that blame structures and ape training facilities remain disassociated in their interests.
~100 years ago - The first ape societies are constructed without a god-based blame structure. As such, something of a "cult of personality" forms around many of their ape-dictators, who are both loved and feared. Apes seem not to have come very far in the past 35-40,000 years, as they seem to have returned to square one. They divorce the alpha male ape from his reality and assign blame and praise to him as their mental concept of him. Not unlike a deity (except he is in fact based on a real ape).
~50 years ago - Atheism, along with anarchy (the belief that ape law is generally unnecessary as long as all apes agree to be nice to each other) begin to assert themselves. In reaction, apes in power put the word "god" on the pieces of paper and metal they trade, as well as into the chant they make their schoolchildren say every morning in their ape training facilities. Take that, founding apes!
Present - The debate rages between apes who claim that apes created god and those who claim god created apes. The latter cite as evidence a book written by dozens of apes who were just learning to write, later translated into hundreds of ape dialects hundreds of different times by apes who were only slightly literate in a time when most apes were completely illiterate. This collection of ape symbols, they claim, put into this particular order, is proof that their blame structure is the correct and only set of beliefs apes should be allowed to have. Most apes, to their credit, couldn't care one way or the other, including apes with either belief set (to say nothing of those with completely different belief sets from either). On both sides, a small collection of apes brings down the blame structure of the other side onto the heads of those of like belief.
2,000 years hence - Apes have learned that they need to cooperate to survive and that the entire concept of blame was flawed to begin with. They work to save the global ape society, but millennia of ape warfare has depleted the natural resources they relied on for their infrastructure. Atheism flourishes, for a time.
5,000 years hence - Ape civilization collapses under its own weight, and suffers the consequences of millennia spent using up the very nature they were claiming to celebrate and protect in the name of killing and indoctrinating apes who didn't celebrate and protect it in exactly the same way they did. Some apes survive and retreat into what wilderness remains.
7,500 years hence - The remaining apes, over time, have learned and taught their children to blame the atheists who were in power when civilization failed for its fall. As these loose conglomerations of apes begin to gather again, they vow never to let the atheists have power, control, or life ever again.
12,000 years hence - As the new ice age encroaches, apes find they must work together to survive...