I was a little unclear. Asia never conquered Africa or vice versa. But at any rate, for most of the time the ecology of Europe was not an advantage.
Geographical determinism is a bit tricky.
To me, Malthusianism goes out the window as even a partly valid theory with the agricultural revolutions that preceded the industrial revolutions of the 19th century in Europe. Yes, Diamond is really getting tangled here. So, a conquering mentality does not automatically follow even from population growth. Also, conquering other peoples increases your population more, as opposed to spinning off groups to unoccupied land. Seems to me conquest mentality is a byproduct of a society with exploiting classes.