Milankovitch theorized that "something" caused and still will cause the Earth to go temporarily out of circular orbit approximately every 108,000 years. This temporary periodic eccentricity of the Earth's orbit explains the 17 ice ages the Earth has had in the last 1.8 million years. Ice ages, or "cool periods" have been shown to linger for up to 100,000 years and in between each "ice age" there have been warm "interglacial periods". The shortest interglacial period was approximately 8000 years, and the longest interglacial lasted approximately 12,000 years. The interglacial period we are in now started about 11,800 years ago, causing all the scientists, archaeologists, and historians to think that they are the first "civilization" on Earth. How positively presumptuous.
       Previous "cultures" sprang up in previous interglacial periods in the "recent" 1.8 million years past. Never, of course, with this many people breeding and breathing. When the weather changes, the "culture" has gone back to "cave-man" "hunter gatherer" orientation except for the ones who have been, for "time" immemorial, prepared with underground habitation, stores of food and forms of "aerial" transportation to get them around to the various "garden spots" still on the Earth, appearing as "angels from heaven" to the primitive survivors of apocalypse.
    Worldwide similarities in various ancient mythologies and accounts descend from a common unknown terrestrial culture (aryans). The common unknown terrestrial culture came here from Mars. The ancient libraries were purposely destroyed to provide certain of our ancestors anonymity. Voluminous lies were told to obfuscate the truth. It's no wonder that ordinary folks think we descended from apes. Intelligent humans, not "cave-men", have been cyclically "evolving" and "devolving" on this Earth for at least a million and a half years.