Prehistoric art
Rachel Armstrong
If varnish is something we paint on wood, how can rocks have varnish? Who paints it?
Imagine a “living paint” so slow-growing it takes millennia to form—a dark, glossy layer called rock varnish, created by microbes feeding on manganese carried by wind and rain. Tough as armor yet thin as a coin, this natural coating became the perfect canvas for ancient artists. Across deserts and cliffs worldwide, early humans carved petroglyphs into these microbial surfaces, leaving behind spirals, animals, and scenes older than the pyramids. Formed by bacteria and fungi over thousands of years, rock varnish stands as a bridge between geology, biology, and human history—an enduring record of both nature’s artistry and humanity’s imagination.