There is a theory that languages move from one morphological typology (isolating, inflected, agglutinating) to the next in a usual, predictable cycle.
What evidence is proposed to support this theory?
As background, I am also familiar with natural sciences and usually things move to the most stable state (macroscopically. for example, things go down, hydrogen atoms fuse to become helium atoms, etc) and do not naturally go back without external force. I am wondering why this isn't the case for languages and why languages go in cycle instead.