Religions spreading by themselves?

[NintendoTogepi]

In the last game I was playing, I founded Islam. This was an accident. I had a Great Prophet and wanted to settle him, but I accidentally clicked "Help Research Divine Right". I tried not to spread it (deleted the missionary, never built any Islam Temples or Monestraties) yet there were still some Muslims in Berlin, and it somehow spread to 1 town of Sitting Bull, even though I had not even been to the continent yet at the time it spread.

How could it have spread to that town when I had never even been to the continent? (I only knew of it's existence from a map that one of my allies gave me) I hadn't even met Sitting Bull yet!

Another game a while ago, I was playing as Gandhi. I immediately went and founded all religions, but deleted the missionaries and never built any buildings for all of them except for Buddhism. At first this was successful, there was nothing but Buddhism.

However, later, I noticed some of the other religions were being founded! By the time I got close to the end of the game there were huge amounts of Islam, Taoism and Judaism, as well as some pockets of Hinduism, Confucianism and Christianity! How did they spread?

I'm just wondering....does the game make them spread on themselves to prevent having only one religion?

 

[Mesousa]

Religions can spread by themselves along trade routes to cities that don't have a religion yet. If you have trade routes with civ A, not with civ B but A has some with B, a religion can spread from you to B along the trade routes too, that's probably what happened in your Sitting Bull case.

If you want the world to have only one religion, spread that one aggressively with missionaries and found all religions yourself. Which is practically impossible on the higher difficulty levels.

 

[OTAKUjbski]

See: Dona Eis Religions.

EDIT: See also: http://forums.civfanatics.com/showthread.php?p=4837863#post4837863

The most important piece of information to take away is that religions can spread through closed borders but not through war zones.

So if any civ you can trade with or your trading partners can trade with have a chance of spreading to or receiving from you a religion!

And like Mesousa said, even if you don't know Civ B, if you can trade with Civ A and Civ A can trade with Civ B, then your religion has a possibility of spreading to Civ B.