Ten thousand years ago, Stone Age hunter-gatherers built houses, tracked game, and conducted elaborate shamanic rituals among the wetlands of North Yorkshire in the United Kingdom. When archaeologists uncovered this Mesolithic dwelling known as Star Carr in 1948, they found well-preserved headdresses made of deer antler, as well as animal bones and wooden and bone tools. Revisiting the site 50 years later, researchers discovered its waterlogged wood rapidly and mysteriously breaking down and many of its bones literally turned to jelly. These “jellybones,” as the authors refer to them in a paper published today in the Proceedings of the National Academy of Sciences, have only arisen recently because Star Carr’s mucky, low-oxygen wetland prevented the site’s archaeological treasures from breaking down. But as the land was drained for agricultural purposes in the late 20th century, the groundwater level lowered, creating dry zones and exposing sulfurous sediment to oxygen, producing sulfuric acid. The acid ate away the bones’ calcium, leaving behind spongy collagen fragments (like the one seen above). To see how the materials might fare in years to come, the team put bone and wood samples in vats with various sedimentary compositions and acidities—each corresponding to environmental conditions found within different regions of Star Carr—and left them for a year. In wet, high-acidity vats, fresh bone turned to jelly and wood’s lignin—a molecular structure found in plants’ cell walls—deteriorated. In drier environments, the jellybones disintegrated entirely. All signs point to the site’s preserved materials rapidly disappearing if Star Carr’s hydrology can’t be changed quickly—and that may already be impossible, as simply pumping more water back into the system might not be enough to reverse its acidity.