A new paper in PLOS Genetics claims to have found a higher frequency of deleterious mutations in the exome of French Canadians than in the French. French Canada was founded by a small population (effective Ne about 2900), but I think that bottleneck has little to do with this increased load. If this result is correct, I see only two possibilities: either the original settlers already had higher-than-average load, or they were subject to relaxed purifying selection.
We all know that purifying selection is considerably weaker nowadays in the decent parts of the world, what with chlorinated water and doctors that cure more often than they kill. But when you think about it, some recent fast-expanding settler populations must also have been subject to weaker than typical purifying selection, just because they had plenty to eat and relatively low disease incidence. In premodern Europe, maybe half of the kids lived to grow up, and the numbers for hunter-gatherers are in the same ball park. But in colonial New England, it was more like 90%, and I would guess that the numbers were similar in Quebec. Cold weather helped. Selection wasn’t as relaxed as it is today, but survival was a lot easier than it had been in typically Malthusian human societies – and in some cases, the process went on longer than modern medicine has existed (only 3 or 4 generations). It’s not high paternal age: that was Euro-typical, around 34.
The Frogs have had it rougher than the Canucks.