The Memory Alpha page on Cardassian history talks about an ancient civilization on Cardassia called the Hebitians, who were supposedly peaceful and spiritual. Due to lack of resources as well as famine, the Hebitian way of life was destroyed and a more militaristic Cardassia developed. This is referenced in the TNG episode "Chain of Command: Part 2". Still, I'm curious, is it ever revealed if the Hebitians were just ancient Cardassians or another sentient race eventually destroyed by famine and impoverishment?
The only fully canon reference to the Hebitians is in the episode you've mentioned, "Chain of Command, Pt II".
MADRED : I understand that you are a student of archaeology. Did you know that Cardassia boasts some of the most ancient and splendid ruins anywhere in the galaxy?
PICARD : I know that the burial vaults of the First Hebitian civilization are said to be magnificent.
MADRED : Apparently when they were first unearthed, two hundred years ago, they were. The burial vaults contained unimaginably beautiful artifacts made of jevonite -- a rare, breathtaking stone. But most of those objects are gone.
PICARD : What happened to them?
Madred smiles slightly, shrugs.
MADRED : What happens to impoverished societies... the tombs were plundered, priceless treasures stolen... a few were preserved in museums... but even those were eventually sold in order to pay for our war efforts.
It's pretty clear from the dialogue that the Hebitians were a culture of Cardassians that predated the current era (apparently they are among the most ancient in the galaxy, clearly a fatuous statement but one that goes unchallenged by Picard).
There's no specific reference to their culture being destroyed by famine, rather it's their tombs and artifacts that were looted in order to pay for an advancing military and food supplies from offworld.
The closest analogy would be the ancient Egyptian tombs discovered in the Valley of the Kings.
The Hebitians are mentioned (in passing) in other star trek properties, most notably "New Worlds, New Civilisations" which contains a story called "The Glories of the Hebitians".
This story makes it clear that the Hebitians were/are Cardassians.
As I admire these ancient treasures, I find it difficult to believe that I'm on Cardassia Prime. This trove of magnificent, jeweled artifacts seems out of place, not the handiwork of the austere Cardassians. Of course, they didn't call themselves Cardassians at the time of this chamber's construction.
In those days, they called themselves Hebitians.
The Hebitian Age, also known as the Age of the Five Kingdoms, was a golden one on Cardassia Prime. It was a time of peace and plenty that began some six thousand years ago and didn't break its stride for nearly four millennia.
But there's a good deal more than the passage of time separating modern Cardassians from their ancient antecedents. Where Cardassians are ascetic to the point of obsession, the Hebitians were in love with excess. Where Cardassian art is relentlessly didactic, Hebitian murals and sculptures were designed only to stimulate the senses. Where Cardassians pride themselves on precision and formality, the Hebitians were almost perversely spontaneous.
and in "Terok Nor : Night of the Wolves"
One of them emerged from the house then, and Miras felt her breath catch. The woman was a Cardassian—or, at least, she had the same Cardassian cranial ridges, with dark hair and pale gray skin.
She’s Hebitian. The awareness dawned on her like the early light that played across the fertile land. An ancient ancestor, from the first great civilization to arise on Cardassia Prime. Miras had been to see the Hebitian ruins, and she realized suddenly that she was not on another world, after all. She was in another time.
THere's also an extensive description of Hebitian culture in "A Stitch in Time", written by Andrew J. Robinson (AKA Elim Garak).
I've edited for brevity and relevance:
“Elim, have we ever spoken about the first Hebitians?” Father broke the silence with a question so strange it almost made me laugh. “No,” I carefully answered. “What do you know about them?” “They were . . . the first peoples . . . before the climatic change.” Our school histories never spent much time talking about the Hebitians. “They had primitive solar technologies. When the rain forests and grasslands were taken over by the deserts, they died off. They couldn’t adapt.”
The first Hebitians had an advanced culture that was sophisticated on every level, Elim. Yes, it was solar-based, but they were able to support themselves, and this is what most of the planet looked like.” He waved his tea container to indicate the Grounds. The idea was almost too outlandish for me. Soft and green places are rare on Cardassia.
“Do you remember, Elim, when I took you to the Hebitian remains outside Lakarian City?” “Yes.” I was just a boy then, and we had walked around the crumbling walls and piles of stone and pulverized tile. I had enjoyed the trip more for its novelty than for anything else, but I remembered one carving on the side of a wall. It was of a winged creature with a Cardassian face that was turned toward a sun disc. Extending down from the creature’s body were several tentacles that divided just before entering the bodies of people who were standing on a globe and looking up to the creature. The tentacles went through the people and into the globe itself. I told this to Father and he laughed.
“Who were their enemies?” I asked, fascinated and somewhat uneasy with what Father was saying. “We were.” The paradox stopped me. “But . . . how is that possible? We . . . we are descended from those people.”