Changing man: By Theodosius Dobzhansky. Science 155: 409–415, Jan. 27, 1967

Abstract

1.1. The relative frequencies of occurrence and subsequent alterations in skeletal and muscular morphologies, molar and canine relations, open-bite, and cross-bite between the ages of 2 and 8 years were studied in 116 children attending the University of Melbourne Child Growth Study.2.2. Children in whom digit-sucking persisted revealed a statistically significant increased proportion of Skeletal II dental base relationships, tongue-thrust activities, lip-to-tongue resting positions, and open-bite tendencies. Those who had discontinued the digit-sucking showed low frequencies of occurrence of these features.3.3. The molar and canine relationships of the group did not change materially during the serial examinations. The occurrence of these molar and canine relations was not different, statistically, for nonsuckers, dummy-suckers, or digit-suckers. Although the children who practiced intense and frequent digit-sucking did show a tendency toward increased frequency of unilateral Class II relations, these relations existed at the age of 2 years.4.4. The incidence of cross-bites did not differ to a statistically significant extent among children who engaged in dummy-, finger-, or thumb-sucking and those who had no nonnutritive sucking.