Progress brings hope, hope brings progess.
—A common Progenitor phrase
The Progenitors were an ancient, sometimes negatively referred to as "antiquated" or "antique", species originally from the Cradle, a separate galaxy from which a number of other such species also originated and, in time, migrated away from. Following the War of the Ancients, the Progenitors went with the other members of the United League on the trek to find new lands to call home in other galaxies, deciding to accompany the Ethereals, Eternals and Kalendin to the galaxy, where they all settled in what would one day become the Ethereal Demesnes. The Progenitors, specifically, settled in what would be known as the Eidolon Expanse, in the sector of the same name.
The Progenitors, being considered the greatest of all United League scientists (and having a record to validate such a claim), long feared that their doom would be inevitable following the move to their new homeworld of Archaiam. After all, even their Eternal allies, who had the skill to see the past, present and future, saw no way for their own survival to play out in this reality. Similarly, the Ethereals had already begun efforts to transfer much of their evolution, both cultural, linguistic, and the like and in a literal, genetic sense, to their selected "successors", the Ethereal Humans. Perhaps worst of all, the Kalendin had let such fears overwhelm them to the degree that they no longer had much in the way of focus or perspective save efforts to protect what little was left of their once-great society.
Thankfully for their own sakes, the Progenitors were gifted with the ability to use the Force in a particular way that not all species could, and few could do as well; for science. Learning from the choices and actions of all three of their allies of old, the Progenitors worked simultaneously under the Eternal-like assumption of their own extinction, feverishly trying to preserve and record as much as they could, under the Ethereal-like premise of creating a race of "successors", the Progenitor Humans, and under the Kalendin-like concern that if they did not act now, all that they were, all that their storied race had achieved, might be forever lost to time.
As their allies died out, slowly and painfully, one race at a time, the Progenitors grew ever more desperate; with time, as their numbers continued to dwindle, they began actively living with and directly guiding the Progenitor Humans, forming a sort of symbiotic relationship in which both species could equally share their lands, acting as one, common society. In fact, with time, little distinction was made within Progenitor daily life between the ancient race and their modern, Human successors, and in this, the classical scientists discovered their salvation purely by unintentional, accidental effect of the combination and culmination of all their preservative actions up to this point; though the Progenitors' numbers had fallen to mere tens of thousands millennia ago by this time, they came to a startling and relieving discovery, that of their population finally stabilizing. They had succeeded where the ability to see all of time had failed the Eternals, where skills, adaptability and commitment to creating worthy successors had failed the Ethereals, where even focusing on nothing but self-preservation had failed the Kalendin- the Progenitors had saved their race from extinction.
Unfortunately, their population never truly recovered in any significant way. Even millennia later, by the time of the Battle of Yavin, they still numbered barely half a million as compared to the billions of Progenitor Humans their work had led to. And, similarly, these Progenitor Humans never became more than a minority of the Ethereal Demesnes, which remained forever dominated by the Ethereal Humans, but both races of Progenitors were respected and valued, and all efforts at governance, colonization and science within their home sector involved their consultation and observation. Also regrettably, the Progenitors' knowledge and high sciences of eons past had long since dwindled, expended in their efforts with their Human counterparts.
Though, some significant things still remained, things which set aside Progenitor science and technology from most others in the known galaxy. Programmable Matter was perhaps the most widely-known of these among the greater galaxy, and even this was considered more of a myth or tall tale than fact among those relative few who'd heard of it. With this technology, the Progenitors and Progenitor Humans could form their weapons, devices, armor and the like on demand, conveniently storing it when not needed and easily reshaping it into whatever form was needed at a given time. Another useful science of theirs was a particular form of cloning later used by the Circle of Fifteen, among others; Artificial DNA. Though the Progenitors long possessed inarguably the most advanced and convenient variation of this science, others did discover how to use it, such as doctor Areana Ketar. Through Artificial DNA, one could essentially "clone" an entirely new individual or individuals of whatever species one might desire, needing only examples of that species' genetic code in-system to be fully functional.