Whose theory first explained continental ice sheets in the last ice age?

Scottish scientist James Croll proposed in the 1860s and 1870s that changes in Earth’s orbit and feedbacks in ocean circulation could drive ice ages. His ideas came before Milankovitch’s later, more detailed calculations, but they were an important foundation for glacial theory. Croll’s work helped scientists think about climate as a dynamic system rather than a fixed background condition. His contribution is now recognized as a key step in paleoclimate science.