Wouldn't the fact that there are headstone markings (or, heck, headstones at all) provide a whole lot of evidence that humans were intelligent, and/or technologically advanced insofar as they could make fine pieces out of stone?

@HDS 226868: The headstone markings look rough and banged up, and for all they know, the markings could just be graffiti

@HDE226868, and architecture, and coffins, and jewelry, and maybe remains of clothing. Especially the finishing would give lots of clues about the technology level

Unless these intelligent species are alien colonists, but less than 3000 years is far, far too short for intelligence to evolve from humans. If humans were to go extinct today, there would still be plenty of remains from our cities (I recommend watching "Life After People" on Youtube).

@Rafael: But that stuff will have to last nearly 3,000 years

@SealBoi: Their aliens

@MindX jewelry and metallic joints will certainly last. Coffins commonly include glass, that would be there too (though broken, probably). Depending on weather, wood would most probably survive too, and if climate is dry enough you would see clothing, skin and even organs

@Rafael: Okay. Answer my question

@MindX Sorry, the "primordial ancestors" bit threw me off.

@SealBoi: Yeah, the aliens had some colonies sent to Earth, and are know trying to find out what happened to them. Sorry I shouldn’t have put in the word primordial

"the markings could just be graffiti" - that still betrays intelligence and tool use. Some of the headstones themselves wouldn't be local, and their being carved eliminates the possibility of them being foundlings (rocks moved by glaciers). Even the preliminary evidence points to sentience. Unarguable evidence is extremely probable to present itself no matter where you dig, e.g., glass beads.

@Mazura: No, graffiti from one of their own species, not the humans they are studying

Further listening (and what may have inspired this question?) here

Don't millenials get buried with their mobile phones?

@Sentinel Yes they would - they wouldn't be seen dead without them.

Why are we focusing on just a cemetery? If they are excavating, there would be other evidences of technological prowess beyond a cemetery.

The remains of a forgotten security tag on the corpse's suit?

If they were lucky they'd stumble across a "digital tombstone" - google it. Then they'd not only have evidence of technology, they'd be able to watch a video and see what life was like in the 21st century.

If it was graffiti from one of their own, then the chain of custody of the evidence is broken, and now we have to get into explaining stuff like how the moon landings were faked, which I will not entertain. These people know they're finding things in undisturbed soil or they're not very good archaeologists.

Enlarged frontal lobe?

It shouldn't be hard to prove intelligence--but intelligence of what? It could be a pet cemetery.

I feel the timescales are pretty far off. There must have been some major global devastating memory and culture loss for this to even make a tiny amount of sense, considering how well we know the history of the human race 3000 years back. We even have books written back then (I've read three). I find that this would be easier to answer if you include details about why everyone suddenly forgot everything.

And also in 3000 years it's highly unlikely for a species to change that much. I don't have sources to back that claim right now, but I'm sure that's not hard to find. What I'm saying is that humans only 3000 years apart are equally intelligent. What differs though is their knowledge sets.