So people from high-birthrate countries move en masse to Europe, then what?

**will they continue having lots of kids? After all, the reason for high birthrates in their home country is for social and economic security but that won’t be needed in Europe.

**living in the more-developed economies of Europe, their birthrates will drop; this is fundamental demographics–fewer infant deaths, no need for so many children, birth control, female emancipation.

**if they do continue having lots of kids for a generation or so, will these kids want to pay the high taxes to support hordes of elderly French/Italians/Spaniards?

**or will it end up like the Mongols who invaded China: seduced into the easier, less rigorous way of life, becoming Europeans themselves after a while?