[cgriswald]

Well, that's... incorrect. Cooper actually says, "They're not 'beings.' They're us," and later says, in response to TARS saying that people couldn't build the tesseract, "No, not yet, but one day. Not you and me, but people." I really don't see any wiggle room in the actual events for claiming Cooper believes they are anything but human; or at least beyond human. But he sees them as an extension of humanity.

Whether Cooper is right may be an open question, but the film heavily implies it. That 'first contact' turning out to be Cooper may be evidence of wrongness, but we don't necessarily need that since we know the characters are not omniscient, and in the context of the film it implies that there aren't any aliens. There are also no signs of any other life, despite several habitable planets. Frankly, the film doesn't even make sense if "aliens did it"; any message of hopefulness about human spirit would fall apart.