Barns were originally unpainted not red. By the late 1700s, farmers began protecting their barns from the elements with a protective paint that consisted of skimmed milk, lime and red iron oxide (red ochre), which is abundant and easily obtained from soil. Barns painted red became a tradition that continues to this day.

Red ochre and human evolution and culture are intertwined. Recent finds in Africa have pushed back the start date for our species’ use of ochre, suggesting that modern human cognition may have developed earlier than we thought. Researchers now suspect ochre may have fueled both brain development and our species’ expansion around the globe. Ochre use appears limited to the genus Homo, but the material’s attractiveness is likely rooted in an adaptation that occurred about 23 million years ago in an early primate ancestor: trichromatic vision. Old World monkeys, apes and hominins - the branch of the ape family tree that includes humans - inherited an ancestor’s ability to see red.

As our hominin lineage became both more social, trichromacy conferred a selective advantage over dichromats. Detecting the color red helped our distant ancestors discern which fruits were ripe and ready to eat, and which leaves were young, tender and more easily digested. 

Red ochre has played a pivotal role in discussions about the cognitive and cultural evolution of early modern humans during the African Middle Stone Age. Evidence for the processing and use of red ochre pigments has been dated by archaeologists to around 300,000 years ago, the apotheoses of the practice coinciding with the emergence of Homo sapiens. Evidence of ochre's use in Australia is more recent, dated to 50,000 years ago, while new research has uncovered evidence in Asia that is dated to 40,000 years ago.

Pieces of ochre engraved with abstract designs have been found at the site of the Blombos Cave in South Africa, dated to around 75,000 years ago. In Wales, the paleolithic burial called the Red Lady of Paviland from its coating of red ochre has been dated to around 33,000 years ago. Paintings of animals made with red and yellow ochre pigments have been found in paleolithic sites at Pech Merle in France (ca. 25,000 years old), and the cave of Altamira in Spain (ca. 16,500–15,000 BC). The cave of Lascaux has an image of a horse colored with yellow ochre estimated to be 17,300 years old. Neolithic burials may have used red ochre pigments symbolically, either to represent a return to the earth or possibly as a form of ritual rebirth, in which the color may symbolize blood and a hypothesized Great Goddess