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Development in a desert shares a fundamental problem with any high-density development: the density of consumption in certain areas vastly exceeds the density of natural resources. This happens most easily in the desert, whereas, e.g., in Polynesia the density of natural resources is very high (fish, volcanic soil, breadfruit/coconut). In the desert you have no choice but to centralize; in the forest you can avoid it, and in the most fertile places on Earth -- New Guinea, the Amazon, the Phillippines -- it has been avoided even today. But relative to the population density of, say, San Francisco, even the highly fertile soil of, say, the San Francisco Peninsula (some coincidence) might as well be a desert. Also to a large extent the world follows _one_ monotheistic religion, which was originally a polytheistic religion (Judaism) and all major monotheistic religions (Christianity, Islam, Judaism, Baha'i, Rastafarianism, Mormonism, the Native American Church) inherit their monotheism, at least culturally, from Zoroastrianism. In fact, the largest non-Zoroaster-derived religions are either polytheistic (Hinduism, Taoism, Confucianism) or nontheistic (Buddhism, Jainism) with the exception of Sikhism. So perhaps the dominance of monotheism really results from the fact that religious conflicts rarely admit multiple victors.