“…irrational numbers, cost accounting, and, yes, religion.” ?? Well, I’d consider the first two of those as synonymous; there are other posters who would equate the first and third!
It’s my understanding that greater brain capacity, used for better interpretation of sensory cues, was a survival characteristic among plains-dwelling omnivorous hominids. An upright stance and the development of forelimbs into hands was a second pro-brain enlargement factor. (“See that antelope? Good eating if we can run it down. See that leopard? Avoid it, or we’re the ‘good eating.’”)
In the Neolithic, specialization developed, where you would spend your time raising cattle, I would raise wheat, Jodi would grind it and produce bread, Phil would produce leather goods from the hides of the cattle you slaughtered, Gaudere would harvest grapes from the vines in the forest (and eventually decide to grow them on trellises), etc. By trading amongst ourselves, each could have meat, bread, leatherwear, and wine. Somewhere down the line DavidB came up with the concept that if one tanned hide is worth three bunches of grapes, and Jodi has two hides to trade but Gaudy only five bottles of grapes, Gaudy should give Jodi a token redeemable for a bunch of grapes when her next vine ripens. From there it was all downhill to international conglomerates. Meanwhile Contestant #3 has been observing the sky, since we all need to know when it’s likely to rain, and since his knowledge is urgent to us, we’ve been providing him with hides, wine, and so on to keep him watching instead of out providing for himself.
The ability to create abstract concepts seems to come fairly early in a child’s cognitive development. Some students of animal behavior suggest that some of the “higher” animals can abstract at some level. Once you’ve gotten this ability, it’s all downhill to SDMB Great Debates and the lesser pinnacles of human achievement.