Jim Vieira isn’t convinced that giants once roamed North America, but he’s willing to stake years of research and his professional reputation on finding out.

The 48-year-old Massachusetts-based stonemason has spent seven years scouring the country for evidence that an abnormally tall race of human-like creatures with double rows of teeth lived here many thousands of years ago. He explains his work is of the historical detective variety, as he digs into accounts as recent as 100 years ago and mythology tracing back to early civilizations that hint at a lost race of giants who once roamed the earth. His education in economics and training in stonework has little to do with the bones he hopes to find, but he has spent the past seven years making a name for himself as an amateur archaeologist, pouring through historical accounts and searching for mysterious stone structures in search of the skeletal remains of a forgotten civilization.

Vieira realizes this mission makes him the butt of an endless onslaught of skepticism and criticism. “You touch this subject as a professional you’re labeled a nut immediately,” he says. But he’s going mainstream with his theories, alongside his brother, Bill, as the subject of a new History Channel show, Search for the Lost Giants, which aired its second episode this week.