John Henry "Jack" Sewell was born in Minnedosa, Manitoba in 1885. He was married to Alpha Welton, and they had six children: Gwen Vison, Bessie Heron, Margaret Vickburg, Shirley Millison, Bob Sewell, and John "Jackie" Sewell. Sewell worked as a private real estate and insurance agent in Saskatoon, SK until 1946. He then moved to Vanderhoof, BC in 1947 to live with his daughter Bessie Heron. Jack Sewell is primarily known in the Laboratory of Archaeology for his work as an amateur archaeologist in Northern Saskatchewan and Central British Columbia.

Sewell was a founding member of the Saskatoon Archaeological Society (est. 1935), where he served as secretary, treasurer, and president. His primarily research interests were in stone tool typologies and manufacturing techniques. He was a self-taught flint knapper and owned a large collection of stone tool belongings originating from the Saskatoon area and abroad. He bought and sold belongings and raw lithic materials from collectors and dealers located in Canada, the United States, and the United Kingdom. Through study and experimentation, Sewell created an unpublished manuscript called the Manufacture of Stone Tools, complete with diagrams and figures of different methodologies for knapping, drilling, and abrading lithic materials. During his lifetime, the British Museum, the National Museum of Canada, and the Provincial Museum of British Columbia exhibited examples of his tools and created films of his flint knapping techniques.

When Sewell retired to Vanderhoof, BC in 1947, he conducted self-directed archaeological surveys and surface collection along the Nechako-Stuart River drainage area. This work culminated in a 1950 report titled "Archaeological Remains in Central British Columbia" which was published in Anthropology in British Columbia, volume 1. In 1949, he collected surface finds while working as a hunting party cook at Cold Fish Lake, BC. In 1950 and 1952, Sewell was invited by Charles Borden to assist with the excavations of Chunlac Village and the survey of Tweedsmuir Park.

Jack Sewell died on October 1, 1953, in Vanderhoof, BC. He is buried with his wife in Saskatoon, SK.