Differential human growth restudied.

GROWTH curves (Statistics); HUMAN growth; QUADRATIC equations; ALLOMETRY; POPULATION

Background: The study of differential growth in various animals suggests that a similar growth pattern occurs throughout the bilateral animals. This growth pattern is based on the assumption that a quadratic equation describes the relationship between two body measurements, yielding a quadratic parabola in a graphic presentation. Aim: Can human growth be studied by comparing body measurements? If the growth of one body part has a definite relation to the growth of another body part and if this relation can be expressed in a quadratic formula, then important conclusions can be reached. Subjects and methods: An official database of the mean measurements of the Belgian population has been used. Results: (1) The growth in human length is, from the beginning, constantly and negatively influenced by the growth in girth, so it is evident that growth has to stop; (2) The influence of the growth in girth is stronger in females, resulting in shorter females; (3) The growth of the human head is, from the beginning, constantly and negatively influenced by the growth in body length (both sexes show a very similar pattern); (4) Not all comparisons resulted in a quadratic parabola: the nipple distance is constantly at ∼24% of the thoracic girth in males and young females. Conclusion: The study of differential growth by using a quadratic parabola gives the answers to the questions “Why do we stop growing?” and “Why are women shorter than men?”. [ABSTRACT FROM AUTHOR]