Image of Birch Chronology

Use of the rockshelters varied considerably over time. The earliest radiocarbon dates for human use range between 11,000 and 7,000 years ago although the density of artifacts and bones indicates sporadic and light use. The intensity of use increased significantly about 7,000 years ago and maintained a similar level (suggesting regular seasonal use) until 750 years ago when it again increased significantly. This slow increase of use over time may simply be a product of slow population growth in the region.