Although new mothers counting their newborns’ fingers may seem clichéd, in reality the finger count varies from the normal 10 digits more often than many realize. Polydactyly—the presence of extra fingers—occurs in about one out of every 1,000 births.
Polydactyly usually involves an extra small finger—most common in African Americans—or an extra thumb, which is more often seen in Caucasians or Asians. The cause also involves a signaling mechanism during hand formation but in this case, the signal is altered to form an extra digit. In African Americans, an extra small finger is often familial, whereas in most other cases of syndactyly or polydactyly, a strong familial disposition is not seen.