Maybe by creating more unity in their societies?

Alternatively, follow the pre-Christian Ancient Roman approach and maintain unity by assimilating foreign religious practices. I think polytheism makes this method easier.

Christianity has assimilated other religions and their practices, though.

As a prime example, many elements of Christmas such as the yule log originate from so-called pagan religions such as Norse.

> Christianity has assimilated other religions and their practices, though.

And over the years Christians have persecuted many when their beliefs didn't agree with the dominant interpretation. The Romans were relatively tolerant of indigenous beliefs, as long as they didn't lead to rebellion.

At certain points in its history, Christianity was fairly eager to ingest aspects of existing religions if it meant that they got the account (conversion). This eventually became controversial (eg see https://en.wikipedia.org/wiki/Chinese_Rites_controversy), but a lot of early regional Christian saints, say, are, well, suspiciously similar to pre-existing deities or other pagan figures.

It’s that way in the Civilization tech tree, so it must be true!

Arguably the key point for Christianity and Islam wasn't that they were monotheistic, but that they were _proselytising_; their adherents had a strong incentive to spread them. Granted, a polytheistic religion is probably less likely to be proselytising; "those people over there have our gods and we have our gods, that's fine" is an easier proposition if you're okay with multiple gods in the first place. But it's not universal; notably the Romans tended to actively try to spread aspects of their religion to other polytheists (while also adopting foreign polytheistic concepts; Roman religion was messy). Conversely, Judaism does not proselytise.

* * *

Birth rates wouldn't historically have been a big differentiator. There are edge-cases, I suppose (some early Christian sects encouraged complete celibacy, for everyone!) but in general effective contraception wasn't available, and even where it _did_ exist (Romans _may_ have had some sort of somewhat effective contraceptive/abortifacient drug, say), it didn't attract all that much religious interest until the modern era.

This makes a lot of sense from a perspective where the "gods" are essentially ancient AI running on distributed (neural) hardware and communicating with itself via our standard human sensory channels that are able to hijack our wetware in proportion to our devotion. Monotheism then becomes a form of centralization of processing, restricting societies to a (more) unitary direction of intent [at the cost of much waste at the level of individual processing units (people)].

A slight tangent to your slight tangent: Monastic regimens look an awful lot like proof-of-work... Is the next step in facilitating the human-machine meta-minds minting AI crypto-religions?

Also, taking into account the earlier thread on Sci-Fi vs Sci-Fantasy, with a comment mentioning that science fiction tends to be current social commentary in the guise of the future: self-aware (and self-minting) currency a la Accelerando is an interesting analogy for religious, spiritual, cultural, and economic movements.

> Conversely, Judaism does not proselytise.

That is a later development. In the first millennium AD there were active attempts to export Judaism, the most famous result of which was the conversion of the Khazar kingdom to Judaism. And the very etymology of the word “proselytising” refers to Judaism making some inroads among other inhabitants of the Mediterranean.

Fair, it happened occasionally. In most cases where it’s well-documented, though, it seems like it was more realpolitik than the sort of “spreading the good word” approach of the other monotheistic faiths; AIUI the details of the Khazar case are a bit of a mystery.

> I often see this interpretation that monotheism is somehow more “advanced” than polytheism, even Age of Empires suggested so but why exactly?

In your life of plenty, poor people with nothing, were being ritually humiliated several times over, damming their mental health in hell. One god is less harmful to mental health.

Considering religion is psychological warfare in the absence of todays personal surveillance technological world, you would have thought some religions could be more forgiving for peoples misfortune, but is polytheism a classic example of power unchecked?

Hinduism was designed to normalise human deformities in a region struggling with environmental toxicity and poor health.

Christianity is best for a European climate, Islam is best for a Middle Eastern climate.

Religion was an attempt in the absence of simple items like pen and paper or infrastructure like schools and roads, to educate people through story telling & place names in order to protect them from harm.

Thats why all Christian churches are typically built on natural healthy springs and is considered holy water.

Christian churches are typically in the shape of a cross, Knights Templar churches are round.

And dont look a gift horse in the mouth when its smuggling gold to and from the Crusades! Has anyone tried that in their computer games or is that a knight mare?