Some aspects of geography have a profound and unexpected impact upon our lives; what difference does the latitude you live in make?
Take, for instance, the natural production of the vitamin D. It's nice to have, and somewhat necessary for bone health, so humans need it to live with a healthy skeleton. The latitude where you live profoundly affects this aspect of human biology.
Before the handy vitamin shop turned up on our street corner, how did the older versions of humanity obtain this important vitamin? Oddly enough, in addition to that vitamin D found in food sources, it also turns out that we can make our own supply of it if we expose our skin to sunlight. That's a fairly handy biology to have. It's a process that we still enjoy today. It's hard-wired into our species' genes.
Of course, lots of variables get involved in that simple feat. Too much sun? Ugh, that can hurt some of us more than others. The body's natural defense to too much sun exposure is the synthesis of melanin in the skin, which serves to block the UV radiation, which also produces Vitamin D.
So a defense mechanism against UV radiation damage also inhibits the production of a necessary vitamin.
Thankfully, those original folks who produced the right balance of melanin and vitamin D, that is, the best mix of UV protection and vitamin production, lived to make more babies than those who did not, so the process of selection for that mixture showed up in the bodies of those living in the latitude of the Fertile Crescent.
We humans didn't have to give the process much thought; successful reproduction took care of that for us. Given the presence of a certain level of UV radiation and the amount of melanin in early humans' bodies, a stable condition for the production of adequate amounts of the vital vitamin and UV protection arose.
Things never stay the same, though, do they?
Humanity, and the need for space nicely spelled out in The Territorial Imperative by Robert Ardrey...