There is a piece of cloth in Mexico City that scientists have been arguing about for five hundred years, and they still cannot agree on a very simple question: did a human being paint it or not?
The cloth is a tilma, a cloak of coarse cactus fiber, and according to the Nahuatl narrative known as the Nican Mopohua, it belonged to an indigenous man named Juan Diego. In December 1531, ten years after the Spanish conquest, he said a radiant young woman appeared to him near the hill of Tepeyac, spoke to him in his own language, and named herself the mother of God. She asked that a church be built on the hill and she sent him to the bishop of Mexico City, Juan de Zumárraga.
The bishop did not believe him, and asked for a sign. Days later the lady sent Juan Diego to the frozen hilltop, where nothing should have been growing, and there he found roses in full bloom, out of season in the dead of winter. He gathered them into his cloak. When he reached the bishop and let the cloak fall open the roses spilled to the floor. And on the rough fabric was an image no one had painted: a dark-haired, olive-skinned woman, head bowed, hands joined.
Zumárraga fell to his knees...
That cloak still hangs in the Basilica of Our Lady of Guadalupe, the most-visited Catholic shrine in the world.
It has been studied for centuries... In a Church inquiry of 1666, seven professional painters testified that it seemed impossible for a human artist to have made something so refined on cloth so coarse. The fabric itself is an enigma: the tilma is woven from cactus fiber, the kind of cloth that normally rots away within 20 or 30 years, yet nearly 500 years on it has not cracked or decayed.
In 1936 the Nobel chemist Richard Kuhn reported that the colors came from no known source, not animal, not mineral, not vegetable. Some, especially the blue-green of the mantle, match no natural dye of the region, and researchers have described the image as faintly iridescent, its tone seeming to shift with the angle you view it from, an effect they say should not be possible on such a cloth.
In 1979 the biophysicist Philip Callahan photographed it under infrared light and reported that, in the original parts of the figure, he could find no preparatory sketch and no visible brushstrokes, though he also documented many later human additions and touch-ups that had cracked and faded over time.
The strangest claims concern the eyes: in 1956 the first ophthalmologists to examine them under magnification reported something they could not explain. The eyes appeared to contain the triple reflection that a living human eye produces, the images sitting exactly where they should and distorting just as they would against the curve of a real cornea. Decades later the engineer José Aste Tonsmann, using digital enhancement, claimed to find as many as thirteen figures reflected there, each packed into a space about a hundredth of an inch across, which he believed were the people gathered in the room at the very moment Juan Diego opened his cloak.
But the case is far from settled and not every examination agrees. A 1982 study by José Sol Rosales says the image was made with ordinary sixteenth-century materials and techniques. And the doubt is old: in 1556, just twenty-five years after the apparition, a senior Franciscan, Francisco de Bustamante, preached a furious sermon in Mexico City calling it a painting, the work, he said, of an indigenous artist named Marcos.
The image has been contested almost from the moment it appeared.
And that is exactly what makes it extraordinary: this fragile cloth has survived nearly five hundred years of candle smoke, incense, humidity, a nitric acid spill in the late 1700s that should have eaten it away, and a bomb set off directly beneath it in 1921 that bent a brass crucifix and shattered marble around it, and left the cloak untouched. It is one of the most examined objects in human history, and after five centuries the examinations still do not agree. Some of the most brilliant minds who ever studied it walked away certain, and they walked away certain of opposite things...