A fascinating map, although a bit simplistic, which seems to be a theme on that site. This one is, I think, a very complicated subject, but they seem to do a decent job of summary.
They also have a "Map of Religions," again claiming that it summarizes 5,000 years in 90 seconds. I don't have anything nice to say about the map. I'll copy my response below:
Knowing that this was supposed to be a simple map, I still must say that the premise and methodology are flawed, as are some fundamental presuppositions.
- Don't call it a "history of religion;" you should call it what it is - a map of political or military expansion under the guise of religion. For example: many peoples conquered by Muslim kingdoms/caliphates converted to Islam, but many did not - however, you map treated all areas as if they had indeed converted, which is not "simplification" (over- or otherwise), but incorrect.
- A serious flaw in the premise is that one can indeed describe the movement and change of religion over 5,000 years on such a simple scale; it is akin to saying that I can write a calculus textbook on a 3" x 5" notecard in 16 point font.
- The map, like many people who decide to pontificate on the subject, assumes that war undertaken under the banner of religion has something to do with the religion. An unbiased reading of history leads to a different conclusion: that people who want power will use whatever means they can to rally folks around them, and will have no problem using religion, regional pride, etc. to accomplish the task, even if it does not align with their personal beliefs. A very recent example of this phenomenon was Hitler and his apparent pro-Christian stance, when he himself thought all religion was delusional. There are only a few (quite notable) exceptions to this principle.
- Some idiot brought up Christmas and cult-worship here in the comments section - they've obviously not kept up with the pace of scholarship on the issue, which clearly demonstrates that the more likely course of events is that the celebration of Christmas pre-dates pagan Sun worship on Dec 21 by about a century.
Simple maps for simple minds.
If this map is any indication of the methodology, presuppositions, etc., then I dare say the site is good for nothing more than colorful maps.