According to the Solutrean hypothesis, people of the Solutrean culture, 21,000 to 17,000 years ago migrated to North America by boat along the pack ice of the North Atlantic Ocean. They brought their methods of making stone tools with them and provided the basis for the later (c. 13,000 years ago) Clovis technology that spread throughout North America. The hypothesis is based on similarities between European Solutrean and Clovis lithic technologies. Supporters of the Solutrean hypothesis refer to recent archaeological finds such as those at Cactus Hill in Virginia, Meadowcroft Rockshelter in Pennsylvania, and Miles Point in Maryland as evidence of a transitional phase between Solutrean lithic technology and what later became Clovis technology.