Note this quote
When disasters stuck, the Christians were better able to cope, and this resulted in substantially higher rates of survival. This meant that in the aftermath of each epidemic, Christians made up a larger percentage of the population even without new converts.
Now as we have all seen here recently, modern Christians tend to be less charitable than their dark ages forefathers. If charity made them more competitive during times of crisis, will their lack of it now make them less so? Will their meanness of spirit hasten their extinction?
One can only hope.