If I'm wondering if the Emperor of Mankind was a genius, it's because there's no formal clue that He was.

Let's begin with His bio :
He was born in Anatoly, 8000 BC. He reveal Himself to the Mankind in ~28000. Fluff telling, He didn't invent so much things, apart from the Astartes.
Speaking of our time of period 8000 BC to 2000 AD, all major inventions were the fact of known men. I read somewhere that the flame-thwrower was an Emperor invention... that's a bit short for the biggest spirit of all time no ? But in the other hand, I read He was behind all the major inventions, as a counselor, apprentice or hidden master.

About the Astartes, there is stated in one of the HH books (if I remember well) that He created them with the help of the best scientists of the period. Maybe He just was a sort of "director of program"? Or something like that? Did He said "I want this", and the scientists, with all their knowledge, did all the job?

I mean, to be the Emperor request "just" to have the most powerful physiology a man could have (be immortal and sickproof...), and be the most potent psyker of all time (see the true nature of the Warp, and then be able to lead Mankind to survive...), not have a 200+ IQ.

Could it be possible that the Emperor was after all, a man with an average intellect? Was His experience of life (more than 40000 years of life!) giving Him His wisdom, and not an über-intellect?