 Initially, he concentrated his attention on petroglyphs, not only recording the designs, but excavating to recover the tools used and observing the environmental contexts.His Master's thesis, "The Aishalton Petroglyph Complex in the Prehistory of the Rupununi Savannas," submitted to the University of Guyana in 1979, presented ideas elaborated in a 1985 article published in the journal "Advances in World Archaeology".In 1980 he began intensive archaeological and paleoclimatic investigations of the shell middens on the northwest coast of Guyana.