Most of the Roman occupants of Herculaneum were doomed the moment Mount Vesuvius erupted in 79 C.E. Within hours, a cloud of hot volcanic ash swept down the side of the famous Italian volcano, raced over the countryside, and smothered the town, along with nearby Pompeii. Hundreds died. Two new studies reveal, in gruesome detail, what happened to their bodies when the hot ash arrived.
Excavations of Herculaneum in the 1980s and ’90s uncovered the remains of more than 300 people killed by the volcano, mostly in a dozen stone structures next to the town’s beach where boats were stored. Perhaps, says biological anthropologist Tim Thompson at Teesside University, people gathered near these vaults in the ultimately futile hope they could launch boats into the Bay of Naples and escape.
The individuals in the boat houses died relatively quickly: The volcanic ash blocked the entrance to each structure, and the temperature of the air within probably rose to about 400°C—even hotter than a wood-fired oven.
At nearby Pompeii, archaeologists have found bodies preserved as eerie 3D casts that in some cases even reveal people’s final facial expressions. But at Herculaneum, just skeletons remain. Because of this, researchers had thought that immediately after death, the hot ash caused body fluids and tissue to vaporize rapidly, exposing the skeleton to direct burning.
But one new study contradicts that idea. Thompson and his colleagues analyzed rib samples from more than 150 skeletons in the Herculaneum boat houses. Surprisingly, the bones still contained high levels of collagen, a protein that breaks down relatively readily when bones are burned. So it was unlikely that these bones experienced much or even any burning. “That forced us to have another think, to re-evaluate how these individuals died,” Thompson says.
He and colleagues speculate that the people trapped inside the boat houses did indeed die quickly, either from heat exposure or suffocation. Afterward, their bodies began to cook. Skin and muscles swelled, driving moisture from soft tissue inward toward the bone. As the team argues today in Antiquity, this would have baked the skeleton without burning it.
It may seem that making such a distinction is of only ghoulish interest, but Thompson says there is real value in understanding the ways in which bodies respond to heat. Doing so could, for instance, provide new information for forensic scientists attempting to identify bodies in the aftermath of a modern volcanic disaster.
Bioarchaeologist Christopher Schmidt at the University of Indianapolis agrees with Thompson’s conclusions. He has also examined Herculaneum skeletons in the past. “I was surprised how good a condition they were in,” he says. “I expected most of the bones to be really charred and in bad shape. But most show really limited signs of thermal alteration.”
Pierpaolo Petrone, a physical and forensic anthropologist at the University of Naples Federico II, has advocated the vaporization idea. But he says he never meant the term to imply the stripping away of flesh within seconds. A body would need at least 20 minutes of exposure to hot volcanic ash to be reduced to a skeleton, he says—and potentially far longer in cases where people are huddled together as they were in the boat houses. In those situations, the effects of the heat may well have been less severe, he says.
But Petrone argues that some bodies elsewhere at Herculaneum do show signs of dramatic thermal trauma. Over the years, he has noticed that a few of the remains he has helped excavate at the site have skulls showing starlike patterns of fractures radiating from a central point. He concludes the fractures are evidence that, after death, these skulls “exploded” in response to the heat from the volcanic ash, as the brains inside boiled and pressure built up within the skull.
Inside one such skull, Petrone and colleagues have now discovered a glassy black substance that contains chemical signatures of enzymes that are expressed in the human brain. He thinks the black substance is the gloopy residue of the person’s molten brain, solidified into a tough “glass” after cooling. This may then have been protected from decay by the volcanic ash that entombed the body.
“I never saw [anything like this] before in 25 years of excavation and study of this site: It’s astonishing,” says Petrone, who, with colleagues, describes the black substance today in The New England Journal of Medicine.
Thompson agrees: “It’s a great find and the analysis seems really thorough.” It’s possible that the two studies are compatible, he says. His analysis focused on a group of individuals huddled together in stone boat houses, whereas Petrone’s individual was buried alone, apparently as they lay on a wooden bed in a building in Herculaneum that was built from volcanic rock and bricks. “[Petrone’s individual] possibly experienced the heat more directly,” Thompson says.
But Schmidt would like more time to digest Petrone’s ideas. “I don’t want to be critical. If nothing else these are new ideas we can think about,” he says. “But I have colleagues who watch videos of commercial cremations, where the temperatures are [hundreds of degrees Celsius] above what was experienced at Herculaneum—and heads don’t explode.”