To put some concrete numbers around that, by meaningless cosmic coincidence, it happens that around the 45 latitude line, the summer/winter oscillation occurs a

To put some concrete numbers around that, by meaningless cosmic coincidence, it happens that around the 45 latitude line, the summer/winter oscillation occurs at nearly exactly 1/3rd and 2/3rds, that is, in winter you get 8 hours of daylight and 16 of darkness, and in summer you get 16 hours of daylight and 8 hours of darkness. The 45th runs through the northern United States, putting nearly all of Canada in an even more extreme environment, and runs through the middle of Western Europe and the southern part of Eastern Europe. So it's a very significant portion of the northern hemisphere that is subject to these conditions, both by geography and by population centers. So, it's not just a few stragglers at the poles or something; it's a major chunk of civilization. As it happens, not much of the land mass of the southern hemisphere is south of 45S. See https://www.mapsofindia.com/worldmap/latitude-longitude.html https://www.mapsofindia.com/worldmap/latitude-longitude.html , for instance.