End of Eternity's take was that humanity was the oldest race in the galaxy. It was because of Eternity's meddling in space exploration via their time alterations that doomed humanity to never reach the stars. By the time, they had achieved space exploration and FTL travel in the far future, other empires were already there and there was no space for humans.
The 2nd Foundation Trilogy's view was that there were always other races out there, but that they were in a dormant phase when the Settlers begun expanding outwards. The robots were fingered as the ones that sterilized many of these planets that had life on them. So it qualifies as a retcon.