Ancient rock carvings found across the globe were made by human civilisations, long ago, right?
Well...perhaps not. No less an authority than Nasa have suggested they could have been made by aliens, as a test.
The space agency has released a new book (which you can read in full here) on the subject of alien communications -- and as you'd hope it tackles some of the more profound and complicated issues facing humanity.
The title of this tome is 'Archaeology, Anthropology And Interstellar Communications' and asks just how we would go about communicating with a civilisation from another planet.
Edited by Douglas A. Vakoch, the first few chapters give an overview of "search for extraterrestrial intelligence" (SETI), the collective name given to the various projects tasked with this endeavour.
It soon moves on to more precise topics, each by a different author.
The intro to the book states:
"The chapters in this volume combine incisive critique with hope that there is a response to the skepticism behind these critiques. Addressing a field that has been dominated by astronomers, physicists, engineers, and computer scientists, the contributors to this collection raise questions that may have been overlooked by physical scientists about the ease of establishing meaningful communication with an extraterrestrial intelligence.
"These scholars are grappling with some of the enormous challenges that will face humanity if an information-rich signal emanating from another world is detected. By drawing on issues at the core of contemporary archaeology and anthropology, we can be much better prepared for contact with an extraterrestrial civilization, should that day ever come."
It al sounds pretty complex but Jesus Diaz over as Sploid assures us its "quite accessible".
He adds: "I have been going through it and it is truly fascinating stuff."
The section relating to the markings, however, isn't quite as dramatic as you might think - which is why the pronouncement has not made international headlines around the world. Nasa isn't saying the markings were made by aliens, but that it might be useful to assume they are in order to reframe the way we go about looking for signals from other worlds, and how we attempt to make contact.
The relevant section reads:
"Consider again, therefore, the desirability of establishing symbolic/linguistic communication with ETI [Extra-Terrestrial Intelligence]. It is helpful to review some parallels from human existence that pose problems for us today. One of these is "rock art," which consists of patterns or shapes cut into rock many thousands of years ago. Such ancient stone carvings can be found in many countries [...]
We can say little, if anything, about what these patterns [above] signify, why they were cut into rocks, or who created them. For all intents and purposes, they might have been made by aliens."