Old-for-grade girls reproduce but do not mature early: Simply a mechanistic link between educational progress and pace of life?

Abstract

Human life-history theory predicts that low cognitive abilities have coevolved with the fast pace-of-life. Old-for-grade pupils proceed slowly at school, which is usually caused by grade repetition due to low cognitive abilities. We assessed the causes and consequences of slow school progress by comparing life-history traits and measures of growth and performance between old-for-grade and appropriate-for-grade Estonian adolescent girls born between 1938 and 1953 (n=1673). We found no evidence for covariation between early pubertal maturation and school progress; girls who were more than 1.5years old for their grade did not show signs of faster development of breasts and axillary hair. However, their first birth occurred one year earlier than for girls who had passed school at an appropriate rate. Among a subset of girls from Tallinn, a higher grade point average predicted a later age at first birth. Completed fertility and parity did not relate to the rate of school progress. Old-for-grade girls were generally shorter, weaker, and had smaller heads than appropriate-for-grade girls, which suggests that they experienced developmental constraints. The most parsimonious explanation for the observed patterns is that old-for-grade girls were devoid of capabilities required for obtaining tertiary education under the highly competitive environment prevalent in the study period. Our findings emphasize the role of (tertiary) education as a proximate constraint on reproductive rates.