The rate of growth and maturing of twins.

In the years 1966-1976, 50 pairs of Warsaw twins (27 MZ and 23 DZ) were subjected to longitudinal investigations. The twins were aged 9-11 years at the beginning of the observations, and 19-22 at their conclusion. The observations consisted of comprehensive somatic measurements and of the evaluation of biological maturity. The rate of growth of the twins, defined by the magnitude of yearly increments of body height, proved to be more concordant in MZ than DZ pairs. The appearance of the adolescent spurt occurred in the same year in 81% of MZ and ca. 43% of DZ pairs. A very slight relationship was found between the rate of growth and final body height. The attaining of subsequent stages of sexual maturity in MZ twins was concordant in 88%, and in DZ twins in 30-39%, according to the respective stage. The body height curves were represented by means of three numerical parameters.