The world’s oldest color has two distinct answers, depending on whether the color is a naturally occurring molecular fossil or a pigment intentionally used by humans. The oldest molecular color discovered in the geological record is a brilliant pink, dating back approximately 1.1 billion years. This finding reveals the color of ancient microscopic life, a timeline vastly different from the earliest pigments first gathered and applied by our human ancestors.
Discovery of the Oldest Molecular Pigment
The oldest color molecule comes from ancient marine black shales found deep beneath the Sahara desert in the Taoudeni Basin of Mauritania, West Africa. These rocks were formed during the Mesoproterozoic Era when the area was a vast ocean dominated by microscopic organisms. The color itself is a molecular fossil, a chemically preserved remnant of chlorophyll, the primary photosynthetic pigment used by plants and bacteria.
Scientists extracted these molecules, a type of porphyrin, from the crushed rock. In concentrated form, they appear dark red or deep purple, but when diluted with a solvent, they reveal a striking neon pink hue. This pigment was produced by tiny cyanobacteria, a type of blue-green algae. Originally, these chlorophyll molecules contained a magnesium ion. Over geological time, the magnesium was replaced by metal ions such as nickel or vanadium. This substitution chemically fossilized the pigment and caused the resulting dark red or pink color seen today.
Methods for Dating Ancient Color
To confirm the age of the pink pigment, scientists employed two primary methods: dating the rock layers and analyzing the chemical biomarkers. The sedimentary rock surrounding the pigment was dated using Rhenium-Osmium (Re-Os) isochron dating, a form of radiometric dating. This method establishes the depositional age of the black shales at approximately 1.1 billion years.
The pigment itself was subjected to biomarker analysis, a process that identifies molecular fossils within rock samples. This involved extracting the organic molecules from the finely crushed shale using solvents. Researchers then used high-resolution analytical techniques to determine the exact structure and isotopic composition of the porphyrin molecules. The analysis confirmed the chemical identity of the ancient chlorophyll remnants. The excellent preservation of the molecular fossils was possible because the black shales were rich in organic carbon.
The Earliest Colors Used by Humanity
While the pink molecular fossil holds the title for the oldest biological color, the earliest colors intentionally used by humans were primarily red and black pigments. Archaeological evidence shows that Homo sapiens and other early hominins began processing and using these colors hundreds of thousands of years ago. The most widely used color was red ochre, a naturally occurring earth pigment composed of iron oxides like hematite.
Red ochre was a versatile material, used for symbolic purposes such as body decoration and early cave art, as well as for functional applications like tanning hides or as an ingredient in adhesives. The earliest secure evidence for ochre use dates back to at least 300,000 years ago. Black pigments were also frequently used, often sourced from charcoal or manganese oxide minerals. The intentional collection, grinding, and application of these materials represent some of the earliest signs of complex, symbolic thought.