Sometime around 450 CE in the Chihuahuan Desert, one brave soul ate a whole rattlesnake raw. If you think that takes guts, imagine passing an 11mm (0.43 inch) fang afterward. The desiccated coprolite—archaeologists’ term for ancient poop—contained the scales and bones of the snake along with remnants of a small rodent and an assortment of edible desert plants. It’s a great example of how coprolites can give archaeologists a direct (sometimes unnervingly direct) look at what ancient people ate.

The dry desert climate preserves things we don’t always think about. When archaeologists first excavated the layers of sediment in Conejo Shelter, a rock shelter high on the wall of a canyon in Texas’ Lower Pecos Valley, they found nearly 1,000 coprolites buried in a corner near the entrance, which looks like it served as an ancient latrine. Those coprolites provide a valuable record of what ancient indigenous people living in the area ate.

The people who lived at Conejo Shelter were only there seasonally, foraging in the challenging environment of the desert. Their routes through the area would have depended on water sources: the three rivers that meet in the Lower Pecos, along with scattered natural springs and rainwater that collected in reservoirs in the bedrock. They would have eaten desert rodents, rabbits, fish, lizards, and perhaps a very rare deer now and then, along with desert plants like yucca, wild onion, and agave, which they baked in earth ovens. And at least once, someone ate a whole rattlesnake without bothering to skin or cook it first.

Who actually does that?

In a coprolite radiocarbon-dated to around 1,550 years ago, archaeologists found 48 scales, a fang with a hollow venom channel, and bones. Based on the shape of the scales and the length of the fang, it was probably a diamondback rattlesnake, and the person who produced the coprolite—its “author,” in archaeological parlance—probably ate the whole thing in one sitting, skin, head, and all. Diamondback rattlesnakes grow from 1m (3 feet) to 1.5m (5 feet) long (the length of the fang suggests this one was probably a mid-sized specimen), and a dead viper can still deliver potent venom in what the Arizona Poison and Drug Information Center calls a “reflex strike.”

Texas A&M University archaeologist Elanor Sonderman and her colleagues wrote, “We propose that the ingestion of an entire venomous snake is not typical behavior for the occupants of the Lower Pecos or Conejo Shelter.” Or anyone, probably. This find is the only archaeological evidence so far of a person eating the head of a venomous snake.

Of course, plenty of people around the world have eaten snakes, even venomous ones, for a long time. But when the indigenous peoples in the American Southwest and Northern Mexico prepared snake, they typically removed the head, rattle, and skin before cooking, or they at least skinned the snake and then roasted it. In that case, finding an ancient bowel movement with telltale rattlesnake scales and pieces of skull, with no charring or pitting on the bones to suggest cooking, is—to put it mildly—strange.

When in doubt, it’s probably ceremonial

One of the clearest lessons archaeology teaches us is that people are remarkably similar in every time and place, and that means it’s definitely not impossible that the daring author of this coprolite ate a whole, raw rattlesnake on a dare. (“That guy who will eat weird stuff for a dollar” is probably a universal component of human cultures.) But Sonderman and her colleagues say there may be a deeper motivation involved. Like any behavior that doesn’t make sense at first glance, this “unique gastrological event” may have been part of a religious ritual.

According to the religious beliefs of several cultures in the American Southwest, including the Hopi and the Aztec, snakes played a role in either bringing rain or withholding it. In Hopi ceremonies, religious leaders would hold the heads of live rattlesnakes in their mouths in order to give the snakes messages to pass along to the gods, asking for plentiful rains. And farther south, Aztec images depict people celebrating a ritual for the rain god Tlaloc by holding snakes in their mouths, though it’s hard to tell if they’re communicating with the snakes, as in the Hopi ceremony, or eating them as a way of “ritualistically killing the animal in hopes of releasing the rain.”

Sonderman and her colleagues suggest that the ancient snake-eater may have been taking part in a similar ritual. In that case, the humble coprolite offers us a rare glimpse into the kind of moment that usually doesn’t make it into the archaeological record. Big, settled societies often leave behind traces of their ceremonial feasting; because hunter-gatherers live in smaller groups that move around a lot, their ceremonies don’t tend to leave behind much in the way of artifacts and faunal remains.

The things we do for science

“The nature of archaeology among such small-scale societies rarely provides insight into individual actions, events, or people,” wrote Sonderman and her colleagues. The nature of coprolites, however, provides direct insight into very individual actions. Besides revealing where ancient people did their business in relation to the rest of their living quarters, coprolites offer a physical record of exactly what people ate and how they prepared it, along with a glimpse of the local environment and the time of year.

For example, the prehistoric snake-eater had also eaten the expected assortment of local plants, such as yucca flowers, prickly pear pads, and wild onions. The prickly pears’ spines had been removed before eating. Pollen mixed into the coprolite suggested that the meal took place in the spring or summer, possibly after a good rain when yucca would be in bloom.

But studying coprolites isn’t a task for the squeamish. Sonderman and her colleagues first had to cut their dried-out, 1,500-year-old sample in half, then rehydrate it in a solution of trisodium phosphate. They noted that “during the rehydration process, the liquid portion of the coprolite turned black, frequently interpreted as an indication of human origin.”

Unfortunately, the coprolite hadn’t been collected or stored in sterile conditions, so DNA sampling wasn’t an option. But its shape and contents pointed to a large omnivore, and in the Lower Pecos, that can pretty much only mean a human “author.”

The researchers sieved the freshly rehydrated feces to sort its contents by size, then set to work analyzing pollen, macroscopic plant remains, small bones, and a very large quantity of mammal hair. The hair, it turned out, belonged to a small rodent, probably a mouse, whose bones also ended up in the coprolite. Based on the amount of the skeleton present, all the hair, and the fact that the mouse bones also show no signs of cooking, it’s likely that the mouse, too, was eaten whole—but perhaps not by the person who (ahem) authored the coprolite. Instead, Sonderman and her colleagues suggest the snake may have swallowed the mouse as its last meal before being eaten in turn.

Journal of Archaeological Science: Reports, 2019. DOI: 10.1016/j.jasrep.2019.03.032; (About DOIs).