Archaeologists are looking for new clues at one of the oldest known sites of human habitation in North America.

Devlin Gandy, an archaeologist from St. John’s College at the University of Cambridge, and James M. Adovasio, the director of archaeology at Meadowcroft Rockshelter and Historic Village, are conducting research at Meadowcroft Rockshelter in Avella, about an hour west of Pittsburgh in Washington County.

The rockshelter is known to be one of the oldest sites of human habitation in North America. Adovasio first excavated the site in 1973.

The two planned to collect sediment samples of possible human DNA this week from the rockshelter’s deep hole, the deepest and oldest part of the site. On Wednesday, Adovasio and Gandy climbed into the rockshelter, scampering over temporary wooden bridges to survey possible locations to sample bedrock. The DNA will be tested and could unlock new information about when humans first lived in North America from the historic site.

“What we’re hoping this particular enterprise will do is to add another increment to our knowledge about the site,” Adovasio said. “Another piece of information that hitherto we might not have had access to.”

Environmental DNA, ancient DNA shed by organisms, will be taken as a complementary piece of evidence that will be studied and matched to the organism it belongs to. With this information, archaeologists will be able to assess how long those organisms have been around the area.

“If there is environmental DNA left, we will see what information it gives us about the past and the occupation sequence at this site,” Gandy said.

Meadowcroft Rockshelter, a National Historic Landmark, was first discovered as one of the first sites of human habitation in North America when a Washington County farmer found a prehistoric tool in what seemed to be a groundhog hole in 1955. The rockshelter was a campsite for early hunters and gathers nearly 19,000 years ago.

According to Gandy, there are many theories for how people came to populate the Americas and occupy Meadowcroft. The early dates at Meadowcroft indicate they didn’t come through the interior of the continent, which would have been under miles of ice.

Since the 1970s, the site has undergone studies to further look into the first humans in North America. Some of the earliest humans can be tracked through lineage to American Indians still around today, according to Gandy.

“At that time, the chief objective was to employ state of the art methods to understand when humans arrived at this location, what they were doing whilst they were here and how long they might have been here through time,” Adovasio said of studies in the 1970s. “Then we modified our goals through the years adding new techniques and asking new questions.”

Through the studies, a line of over 16,000 years of environmental records was found that included climatic changes, plant and animal changes. The records then provided information on how humans adjusted through these times.

“It appears as it did in the early ’70s, that people were at this spot long before they were supposed to be in the New World,” Adovasio said.