Shovel-shaped teeth is a term used to describe upper incisors that are scooped out like a shovel on the back. Shovel-shaped teeth are a part of a complex of genetic characteristics called sinodonty seen frequently in people of East Asian and Native American descent.
Sinodonty is characterized by several dental characteristics, including shovel-shaped incisors that are not aligned with the rest of the upper teeth. Often, people with sinodonty also have first premolars with only one root and first lower molars with three roots. This is in contrast to most people of European descent whose first premolars and first lower molars typically have two roots.
The gene responsible for sinodonty is the Ectodysplasin receptor EDARV370A gene, or EDAR, which has been traced back to a mutation that occurred in central China about 35,000 years ago. Scientific experiments demonstrate that people with this genetic variant have thicker hair shafts, more sweat glands and smaller breasts than people of European descent. Approximately 90 percent of Han Chinese carry the EDAR gene as do about 70 percent of people in Japan and Thailand. The gene is also carried by 60 to 90 percent of Native Americans who are descended from East Asians. Scientists are unsure what caused the EDAR genetic mutation, and are examining various theories as a part of a larger study to determine how humans evolved.