This theory is based on the premise that the true origin of human civilization goes back farther or much farther than Mesopotamia/Sumeria, and said "civilization" was merely the beginning of recorded or known history, not all intelligent human history. (It should be noted that the Harappan/pre-Hindu people and the earliest known Chinese/Yellow River communities existed at the same time as Mesopotamia). I assume, correctly or not, that at least the oldest megalithic structures (pyramids etc.) are from a lost era of technologically advanced people, though apparently advanced in a way other than technology as we know it now.
It strongly appears there were a morally deficient (to say the least) people who took over sometime between the time of the most ancient megalithics and a certain amount of time before the Sumerians and their contemporaries. The "overlords," or whatever the f they were, of the time might have been, and I personally have a hunch (rightly or wrongly that) they were, involved in genetic-physical manipulation of humans in order to turn them into the most servile and ignorant creatures anywhere, but it's a cinch they, the "Annunaki" (creator "gods" of the Sumerians), were the first ones to introduce religion as the primary way to manipulate and brainwash the population. The difference between the original Sumerian religion and the original monotheistic religion Judaism, which quite obviously was stolen from the Sumerian creation story, was that the Sumerian totalitarianism was completely literal and blatant about humanity being nothing more than a slave race.
Judaism, and then particularly its two overgrown Abrahamic offshoots (Christianity and Islam), were, and still are, more subtle in their enslavement of their subjects, but no less enslaving. They had enough time after Mesopotamia to rework their idea and sell it in a prettier-looking package. It was/is more difficult to resist the attraction of the notion of a Single Creator of the entire infinite, incomprehensible universe.
The utter slavery of the very idea of a "god," and then later an alleged single, omnipotent "God," is the original and biggest example of devolution. (There's no real reason to believe slavery, in any conceivable form, has always been the way for humanity, dating back to prehistory). All intelligent beings have equal rights to equal access to all knowledge and activity that they can actually comprehend and undertake. There simply should be no masters and no slaves. What a concept.
To the religious (or religious enough) people who would say I "just don't get it" and am unable to tap into the Power of God, which simply means the most enlightened portion of the intelligently unseen, to improve and make a real difference in my life, they or you couldn't be more wrong. Spirituality isn't dependent on religion, and one need not be convinced (without proof) of the existence of a Single Creator of the universe in order to be in touch with the divine. There's no need to elaborate further. No worries here.
Forgive me if it turns out I'm just another case of "oops, wrong planet."