I don’t think our bodies expect to experience seasons, I just think our bodies adjust to the seasons as well as it can.
I once argued on a Q that humans became whiter as they migrated to colder climates. Paler skin, blue eyes, blond hair. I had just been in Alaska and when I was in glacier bay there is mostly ice and water and the colors around you are white and blue. Literally some of the ice is blue-ish. Being tan in the summer we blend in with the browner tree tree trunks in the forest. I really see it as a camouflage. But, almost everyone talked about how pale skin absorbs vitamin D better. I do see the logic in that, and I always thought that myself, but I can tell you for me, I am very pale, and can’t be out in the sun for more than 20 minutes without burning. My avoidance of the sun has left me vitamin D dificient, so that was not a perfect system evolution gave me. My husband has olive skin and his vitamin D is always good, but he gets more sun than I do. Anyway, I was also thinking how some Native Americans have more of a red tan, and maybe they lived where the lands were red clay? But, enough of this tangent.
Plenty of people live close to the equator where there is basically almost no change of seasons. If what you suggest is true, they would have all sorts of problems, but they don’t. My happiest time in my life was living in FL with minimal season change. Being warm all the time suited me very well. Having more days of sunlight made me very happy.