Wiseman, you are not giving an example of group selection. You are imagining one single group (or two if we split the rabbits and foxes apart) over a long period of time. With group selection there are multiple groups, some of which die out on their own or get squashed/absorbed by other groups or the groups increase in size and split apart at different rates. For the rabbits/foxes example we could imagine multiple populations all separated and say that in all instances where breeding was not restrained, they overpopulated and died out, leaving only the ones that did restrain. However, all those populations would be vulnerable to the overbreeding mutation suddenly appearing, so it would not be a good explanation.
Wiseman, you are not giving an example of group selection. You are imagining one single group (or two if we split the rabbits and foxes apart) over a long period of time. With group selection there are multiple groups, some of which die out on their own or get squashed/absorbed by other groups or the groups increase in size and split apart at different rates. For the rabbits/foxes example we could imagine multiple populations all separated and say that in all instances where breeding was not restrained, they overpopulated and died out, leaving only the ones that did restrain. However, all those populations would be vulnerable to the overbreeding mutation suddenly appearing, so it would not be a good explanation.