The effect of periodic changes in earth’s orbital eccentricity and magnitude and direction (precession) of earth’s axial tilt on the advance and retreat of ice sheets was first proposed by:

Milankovitch

Explanation:

Milankovitch was the scientists that proposed the theory about the Earth's cycles and how they affect the global climate. The cycles that Milankovitch suggested have been named Milankovitch cycles in his honor, and they are the most accepted theory about the global climate changes on Earth. There are three cycles according to this theory, eccentricity, axial tilt, and precession. All these three combined result in the changes we know as ice ages and global warming periods, with the ice ages being characterized by colder and drier weather, with the ice sheets spreading out significantly and the sea levels dropping, while the global warming periods are warmer and wetter, with the ice sheets being much smaller and the sea levels rising up.

it depends on the situation, but in a definitional sense, irrendentism is more valid.

explanation: