Kythnos can lay claim to one of the oldest known habitations in the Cycladic islands, a Mesolithic settlement (10000 BCE– 8000 BCE) at Maroulas on the northeast coast. The site, close to the village of Loutra, is situated on the shore, and large portions have eroded into the sea. Excavations in 1996 found intact human skeletons, along with stone artifacts and part of a floor pavement, which indicates a long-term settlement, probably of hunter-gatherers.
Third millennium BCE (First Cycladic Period) findings at Skouries near the highest peak of the island, Mt. Profitis Elias, suggest that Kythnos was a supplier of raw materials for metallurgy to other islands during the Bronze Age. Remains of copper smelting sites and open-air copper mines were investigated in 1984-1985. (A recent paper by Myrto Georgakopoulo points to the seminal work here by Gale and others.)