This is a geat series. It puts complexity into readily understandable articles which are not too short and not to long. The graphics are great. I have purloined many of them although I am no longer teaching. Climate (and population) have everything to do with all history (and prehistory). We are soon on our way to do more work on understanding the ridged gardens many North Central Native Americans used for centuries. My wife and I believe all the work that went into them was to create good soil for growing maize where there was little to no good soil tp be found in the area. The climate at the western edge of the Upper Peninsula MI is between lakes Superior and Michigan so it is possible to grow a good crop in that you have good soil and a moderated climate. The work of moving tons of soil made it possible to take advantage of the moderating effects of the lakes.