I have been hearing a lot of interviews with author Graham Hancock lately and I think his line of inquiry will be of interest to Steampunks everywhere and of particular interest to those interested in writing about non-fantastical Steampunk worlds.
In 1996 Hancock published Fingerprints of the Gods . The TL;DR of which is: There is tantalizing evidence that a great, worldwide, civilization existed and was snuffed out by a global cataclysm about twelve and a half thousand years ago.
His new book Magicians of the Godscontinues the investigation and the TL;DR here is: Holy shit! geologists confirm that there were a pair of global cataclysms about 12,800 and 11,500 years ago and OMG we have recently discovered several megalithic sites that date back to a time when humans were supposed to be just hunter gatherers.
So what we think of as the agricultural revolution about ten thousand years ago may not have been the dawn of civilization, but it’s reboot.
One of the tantilizing clues that Hancock talks about are maps drawn in medieval times that cite even older maps as source material. These maps show strange shorelines that don’t match contemporary coasts but do match where the coasts would be if sea level were 400 feet lower. This correlates closely with the calculated rise in sea level caused by the aforementioned global cataclysm (a comet strike). In addition, these maps sometimes show Antarctica, a continent that was not discovered until much later.
And here’s the kicker; the longitude of these elements is consistent and accurate. That means clocks. Damn accurate clocks you can take a sea voyage. So we are talking about a civilization with about an 18th Century understanding of technology and that means steam baby! No ancient aliens are required; the Chariots of the Gods just may have been steam powered!