If Milankovitch cycles are the cause of the periodic ice ages, and those cycles have not changes in billions of years, then why is the 100,000 cycle limited to the past 4 million years, and not seen before for the prior billions of years?
“...why is the 100,000 cycle limited to the past 4 million years, and not seen before for the prior billions of years?”
A lot of that has to do with the changing locations of continents and such things as the closing of the Isthmus of Panama, which affect ocean currents and the amount of land in more polar regions.