The effect of shovel trait on Carabelli's trait in Taiwan Chinese and Aboriginal populations.

Chinese and other Mongoloid populations differ from Caucasoids by having a high prevalence of shovel trait and a low prevalence of Carabelli's trait. This study was conducted to compare the association between the shovel and the Carabelli's traits between Chinese and aboriginal Mongoloid populations. The research is designed to sample randomly a Chinese population and an aboriginal population having low admixture with neighboring populations. The Mongoloid aboriginal group was from the Bunun tribe who resides in an isolated alpine area in Taiwan. The effects of sex and age on Carabelli's trait were controlled in this study, as was the association between tooth size and Carabelli's trait. Our results show that males had more Carabelli's trait expressed on teeth than females in both of these two Mongoloid populations. The buccolingual diameter of Carabelli's trait teeth was larger than that of teeth without the trait. After controlling for sex, age, and tooth size, the existence of the shovel trait significantly increased the likelihood of having Carabelli's trait, especially in Chinese, which implies another significant ethnic feature for Mongoloid identification.