An exception to purposeful burial was discovered when in 1935 the remains of an adult male were discovered under a large boulder. The boulder had shifted and settled onto the victim, a pre-Columbian miner, who had disturbed the rubble supporting it. The remains of the ancient victim were named "Lost John" and exhibited to the public into the 1970s, when they were interred in a secret location in Mammoth Cave for reasons of preservation as well as emerging political sensitivities with respect to the public display of Native American remains. Research beginning in the late 1950s led by Patty Jo Watson, of Washington University in St. Louis, Missouri, has done much to illuminate the lives of the late Archaic and early Woodland peoples who explored and exploited caves in the region. Preserved by the constant cave environment, dietary evidence yielded carbon dates enabling Watson and others to determine the age of the specimens. An analysis of their content, also pioneered by Watson, allows determination of the relative content of plant and meat in the diet of either culture over a period spanning several thousand years. This analysis indicates a timed transition from a hunter-gatherer culture to plant domestication and agriculture. Another technique employed in archaeological research, at Mammoth Cave, was "experimental archaeology" in which modern explorers were sent into the cave using the same technology as that employed by the ancient cultures whose leftover implements lie discarded in many parts of the cave. The goal was to gain insight into the problems faced by the ancient people who explored the cave, by placing the researchers in a similar physical situation. Ancient human remains and artifacts within the caves are protected by various federal and state laws. One of the most basic facts to be determined about a newly discovered artifact is its precise location and situation. Even slightly moving a prehistoric artifact contaminates it from a research perspective. Explorers are properly trained not to disturb archaeological evidence, and some areas of the cave remain out-of-bounds for even seasoned explorers, unless the subject of the trip is archaeological research on that area. Besides the remains that have been discovered in the portion of the cave accessible through the Historic Entrance of Mammoth Cave, the remains of cane torches used by Native Americans, as well as other artifacts such as drawings, gourd fragments, and woven grass moccasin slippers are found in the Salts Cave section of the system in Flint Ridge. Though there is undeniable proof of their existence and use of the cave, there is no evidence of further use past the archaic period. Experts and scientists have no answer as to why this is, making it one of the greatest mysteries of Mammoth Cave to this day.