The author can't even get his facts correct. The above statement is false. There have always been numerous places where polygamy has been legal and honored. It still is, even today, in most of Africa, the middle east, and much of Asia.
The culture which created the Canadian nation is the Judeo-Christian one, which has a tradition of monogamy going back thousands of years - monogamy was firmly rooted in the Roman, Germanic and Pharisaic Jewish cultures from which modern-day Canada ultimately derived.