The Romans conquered many peoples with different local myths, but they incorporated them into the empire by mapping the local deities to their Olympian canon, forming joint entities as targets of worship and devotion. This seems to be a tolerant and scalable approach, given a universe of various polytheisms based on nature, which helps ensure a viable mapping exists.<p>Monotheism has a lot to answer for. It began with Judaism, which has a certain exclusivity, but does not take the missionary position of universal adoption and conversion. It is surely the descendants, Christianity and Islam, where the polarizing missionary zeal of crusade and jihad has caused a lot of trouble. While many religions practice ostracism for the non-believer, only Islam insists on death to the apostate, who is seen as a traitor by definition, even without any further subversive or mutinous action.<p>Unfortunately, the doctrinaire and totalitarian proselytizing religions seem to have been quite scalable and successful. The Reformation and the Enlightenment have successfully turned back the tide of Catholicism in the West, but the challenge to Islam has yet to really get started.<p>Given the exploding demographics of the relevant parts of south Asia, Middle East and Africa, that future struggle gets harder by the hour. Indeed, it is the intensive demographic success of the subjugation of women and the rejection of contraception that has propelled these expansive conquering religions through history. It seems very likely that Japan and Russia will decline in population (no immigration), Europe will be Islamized and North America will be (re-)Hispanized with Catholicism.<p>The Reformed and Enlightened might have liberated themselves into an evolutionary dead-end of personal choice, free from enslavement by community propaganda and intimidation, but ultimately just a fleeting moment of liberty before the incoming tide of ruthless and fertile monotheists.