Compare the development of complex civilizations in the Western Hemisphere with those of the Eastern Hemisphere What factors might account for those differences?

The Western Hemisphere is the hemisphere that includes North and South America; the civilizations that developed in the Western Hemisphere, such as the Incas, Mayans, and Aztecs, were not as complex as those in the Eastern Hemisphere. There are doubtlessly many different reasons why it worked out that way, but it is probably important that the Eastern Hemisphere, including Eurasia and Africa, was inhabited for a much longer time and had more diverse ethnicities with longer histories, which became more competititve with each other than the relatively homogeneous cultures of the Western Hemisphere, and the competition pushed civilization to greater complexity. I would also say that the invention of the phonetic alphabet by the Phonecians was perhaps the single most critical advance of the Eastern Hemisphere.