What is the evidence in favor of paleo?

I re­cently came out against pa­leo in the open thread, and re­al­ized that I prob­a­bly haven’t yet heard the strongest ar­gu­ments in fa­vor of a pa­leo diet. So, what are said ar­gu­ments?

EDIT: Or more gen­er­ally, why should I eat less car­bo­hy­drates and more pro­tein /​ fat?