There were at least six civilisations on Metralubit. During the first civilisation, the Darkness found it and started the feeding cycle. Each civilisation lasted about two thousand years before The Darkness plunged it into chaos. The Darkness fed on the carrion and death created and then went back into hibernation.
The Yelphaj civilisation
While it also fell almost overnight, the Yelphaj civilisation was noted for weathering plague, flood and famine without losing stability.
The Helducc civilisation
The Helducc civilisation had a population of approximately three million, and spanned 40% of the planet. It was destroyed in a conflict sparked by a rivalry between two of its rulers. It was the immediate precursor to the civilisation that occupied Metralubit during the Fourth Doctor's presence on Barclow.
The sixth civilisation
The sixth civilisation was extant when the planet was visited by Romana II and K9. It was a constitutional democracy, ruled by a Premier. Premier Harmock was the incumbent at the time, ruling from the capital, Metron.
The sixth civilisation was developing at the same rate as the first five. Progress was slow and the planet was polluted and dirty. Eventually, Menlove Stokes' cryogenics chamber was found. By extrapolating the knowledge in his mind, they made great leaps technologically. They created the Femdroids from Stokes' memory of K9. These Femdroids were more efficient and intelligent then humans and saw the pattern of destruction.
The Femdroids decided the best choice of action was to send most of the humans to Regus V. The Darkness would be distracted by a war on Barclow. The Darkness would move in to feed and Barclow would be blown up, destroying it.