The massive buried structures at Gunung Padang in Indonesia would be much older than Egypt’s great pyramids — if they’re even human constructions at all.

A headline-grabbing paper claiming that a structure in Indonesia is the oldest pyramid in the world has raised the eyebrows of some archaeologists — and has now prompted an investigation by the journal that published it, Nature has learned.

The paper, published in the journal Archaeological Prospection on 20 October, garnered headlines around the world. Its central claim is that a pyramid lying beneath the prehistoric site of Gunung Padang in West Java, Indonesia, may have been constructed as far back as 27,000 years ago.