Probably the hottest topic in Psychology is Consciousness.
We don't know what it is or where it came from. However Julian Jaynes has given us a striking hypothesis in his book, "The Origin of Consciousness in the Breakdown of the Bicameral Mind".
"The Origin Of Species", by Charles Darwin together with the discovery of the structure of DNA by James Watson and Francis Crick, gave us Biology.
But so far, "The Origin Of Consciousness", does not have the corroboration provided by DNA for, "The Origin of Species". So we do not as yet have a discipline of Psychology.
But it does provide us with a good place to start thinking about Consciousness.