From memory, the Fremen knew that the sandworms were the source of the spice melange but until the arrival of planetogist Pardot Kynes nobody else knew and this knowledge did not become widespread until later. Yet spice had already been an essential commodity to the imperium for over 1000 years. Given the utter dependence on it by so many influential groups and persons, they must have wondered where it came from, if only to establish whether it was a renewable resource and under what conditions it could be optimally harvested. What did people think before the worm-spice relationship was understood?
Where did people think the Spice came from before they knew about the Sandworm life cycle?
3I've said before here that I think the discovery of Spice is in fact relatively recent at the time of Dune. (see this answer for some reasoning), It's at least possible that it had only been known for a few years at the time Pardot made the connection.– Daniel RosemanNov 7, 2021 at 22:20
1@DanielRoseman the Spacing Guild only came to be of relevance because of spice and that it allowed for reliable guidance through foldspace. The Spacing Guild has been relevant for over 10,000 years (since Dune takes place in the year 10,191 AG, or After Guild). The prequel novels (if you accept them) expand on this by having the Spacing Guild established during the Butlerian Jihad, and their vessels and Navigators are in fact instrumental in the defeat of the Thinking Machines during it, and the properties of spice are only discovered then when entrepreneur Aurelias Venport takes an interest.– user25730Nov 8, 2021 at 0:27
Again, nothing canonical says that's the case. We know the BG used other "poisons" before the spice, I don't see any reason to think the same wasn't true of the Guild. In any case, we again have no canonical evidence that the Guild monopoly is due to the spice only.– Daniel RosemanNov 8, 2021 at 14:11
@DanielRoseman - it is in canon. Dune mentions Navigators need spice to presciently predict safest course and to quote Paul from Dune: "Guild (...) must have the spice to exist". Guild's monopoly came about thanks to that Navigator's spice trance.– AcePLNov 10, 2021 at 8:17
1Now they must, just as the BG now need the spice for their agony. Once again, it doesn't say that that was always true.– Daniel RosemanNov 10, 2021 at 9:51
In brief, nobody seems to know or, astoundingly, care all that much. Everyone seems to think that it's a unique biological reaction that takes place on Arrakis.
“You’ll learn about the funeral plains,” she’d said, “about the wilderness that is empty, the wasteland where nothing lives except the spice and the sandworms.
Even the Imperial planetologist feigns ignorance.
“It is mostly dry land biology and botany . . . some geological work–core drilling and testing. You never really exhaust the possibilities of an entire planet.”
“Do you also investigate the spice?”
Kynes turned, and Paul noted the hard line of the man’s cheek. “A curious question, my Lord.”
“Bear in mind, Kynes, that this is now my fief. My methods differ from those of the Harkonnens. I don’t care if you study the spice as long as I share what you discover.” He glanced at the planetologist. “The Harkonnens discouraged investigation of the spice, didn’t they?”
He does admit that worms defend the spice, but he avers that there's a connection between them.
“Ah-h, the worms,” the Duke said. “I must see one sometime.”
“You may see one today,” Kynes said. “Wherever there is spice, there are worms.” “Always?” Halleck asked.
“Is there relationship between worm and spice?” the Duke asked.
Kynes turned and Paul saw the pursed lips as the man spoke. “They defend spice sands. Each worm has a–territory. As to the spice . . . who knows? Worm specimens we’ve examined lead us to suspect complicated chemical interchanges within them. We find traces of hydrochloric acid in the ducts, more complicated acid forms elsewhere. I’ll give you my monograph on the subject.”
In the prequel novels we learn that the Harkonnen have had control of the spice for much of its known lifetime and that they were easily fooled by Pardot Kynes and his son.
Now, the groundcar approached a village tucked into the rocky foothills; it was called Bilar Camp on their terrain maps. Pardot continued to talk about melange and its peculiar properties. “They found spice too soon on Arrakis. It deflected scientific inquiry. It was so useful right from the outset that no one bothered to probe its mysteries.”
Liet turned to look at him. “I thought that was why you were assigned here in the first place— to understand the spice.”
“Yes . . . but we have more important work to do. I still report back to the Imperium often enough to convince them I’m working at my job . . . though not very successfully.” Talking about the first time he’d been to this region, he drove toward a cluster of dirty buildings the color of sand and dust.
Dune: House Harkonnen
Interesting! The most important substance in the known universe. You would think both the Harkonnens and House Corrino would be very invested in having answers to questions such as: How much of this stuff is out there? Will it ever run out? Nov 10, 2021 at 2:25
You would also expect the Guild to be asking themselves the same questions, but perhaps they felt they could rely on their prescience to determine whether reserves of spice in the wild were diminishing. Nov 10, 2021 at 2:29
@Batperson in the Dune novel, at the end, it is stated the Guild cannot seek to control (or, presumably, think too much about) Arrakis and the Guild precisely because it is the source of their prescience. It's a bit hand-wavey, a bit like that "hole" the Bene Gesserit cannot look into but Paul can. So the Guild cannot think too much about the spice -- and they forbid anyone else to look into it as well, because that's their deal with the Fremen. Hence no satellites, etc. Nov 11, 2021 at 21:56
I think there's room for the Space Guild to be pressuring the secrecy, or ignorance if you will. They have backyard deals with the Freman, and through this bottle neck for the spice they have great control over the empire and the houses. For example, they will not at any price allow weather satellites around Arrakis. Mar 17, 2022 at 1:07
At the time of Dune and the later books the knowledge of where the Spice truly originates is never particularly widespread but the choice of POV characters makes it feel that way because most of them know the truth. During the time of Dune everyone knows that the final stages of Spice formation occur deep in the sands of Arrakis but no-one really cares what those stages are or even what the precursor conditions are until Kynes starts to study the planet in greater detail and is welcomed and assisted by the Fremen in ways that outsiders never have been. They know that the spice is a renewable resource because they have been harvesting it for millennia. The interesting thing is that once knowledge of the Spice must have been more widespread.
We learn in Children of Dune that the Makers, great and small, (the Sand Trout and the Worms they grow into) were introduced to Arrakis, by humans. When Leto II and Ghanima Atreides search their genetic memories the last time before they leave each other to enact their plan for the future of humanity they discover that some of their ancestors remember a time when Arrakis was "...once a water world like Caladan. That was before the Sand Trout came." It's never made clear how the Fremen arrival on Arrakis relates to this event. It is also never clear whether the Makers are natural or engineered.
2From a literary perspective- if they are natural given how big space is...stumbling on the original home world of the worms and everyone scrambling to stake a claim while it is a secret would have been worth at least one book. Especially if the worms on Dune are extinct at the time. Per Herbert's environmentalism the desert is a symptom of one species getting out of control - so this hypothetical planet might not be entirely a desert. I cringe at the idea of an engineered pre-Butler bioweapon that happens to make the best stuff ever. Probably best left a mystery. Nov 8, 2021 at 4:43
2@lucasbachmann Unless, like Arrakis eventually is, their original homeworld was destroyed, maybe by the Enemy. I doubt they'd be engineered as a weapon, more likely, if they are artificial, they were created to do exactly what they do. Having not read the Butlerian Jihad my immediate thought when it was suggested that the Sand Trout are not natural creatures was in fact that the Spice came first, as a designer drug, then the makers, then when the first prescient came along, and the invention of the Spice actually lead to the Jihad against the machines.– AshNov 8, 2021 at 4:51
1It seems contrary to human nature that no one would care where the spice comes from. We care very much how oil is formed, and have studied it in depth, even though we are less dependent on oil than they were on spice. Also, the one planet in the known universe which happens to have both spice and sandworms - Surely Paul Atreides wasn't the first to ask the obvious question! Nov 8, 2021 at 6:57
1@Ash Harkonnens gained Arrakis 80 years before events in Dune, as per this quote: "Thufir Hawat, his father’s Master of Assassins, had explained it: their mortal enemies, the Harkonnens, had been on Arrakis eighty years, holding the planet in quasi-fief under a CHOAM Company contract to mine the geriatric spice, melange."– AcePLNov 10, 2021 at 9:11
1@Adament it seems to be more like Valorum is suggesting - people are just not interested in finding out. It seems a very stagnant universe. Technology might be more advanced, but there is very little change or innovation. Nov 10, 2021 at 18:27