There was at least one ancient, highly advanced civilization which had spread all over the world, traces of which can be found in megalithic structures, but this civilization disappeared due to a catastrophic event around 12000 B.C., the same period a shitload of animals went extinct.
I could believe it. Well, depends on what you mean by "highly advanced." I don't think they were making plastics and other stupid chemicals that literally have no foreseeable way to break down, but they were likely doing things on a level we don't reasonably expect them to. The giant structures that seemed hard as fuck to build (Giza Pyramids, Incan Walls in Cusco, Peru) and the things we've found like the Baghdad Battery and the Antikythera Mechanism. People have been smarter for far longer than we give them credit for even if there wasn't a "highly advanced civilization" in 12,000 B.C. There is the whole Bronze Age collapse that we know of, there could have been more before then too. We've been estimated to have been around for 300,000 years and yet the Kish tablet is dated for around 3500–2900 B.C. so we're missing about 295,000 years of the modern human not having records that were able to stay intact to today if we exclude cave paintings. About 50,000 years ago we have what's our oldest cave painting and being generous we still haven't even gotten into the first two-thirds of our existence as we are as Homo sapiens.
I doubt they would have made giant underwater telecommunication cables or gone to the Moon, but they were not stupid either. Hell, I don't really think the modern human's life changed drastically until VERY recently. Think about how long we likely cultivated crops and raised livestock. Around 11,000-12,000 years ago or so? That's something that was pretty average, especially globally, for people in the 1800s A.D. No microwave, no TV, no refridgerator, no lights, no indoor toilet, maybe no indoor plumbing, no hot shower on demand, no dishwasher, no internet, no TikTok, and no hot chip.
alec you better be grateful for the modern world, you'd be smelling the most foul assholes ever back in the 1800s. But I guess the feet were mighty dirty too so maybe that'd be a blessing for you.