Daughters of divorced fathers begin reproducing earlier than daughters of deceased fathers

New research published in Evolution and human behavior found that girls whose fathers were divorced started reproducing about 9.2 months earlier than girls whose fathers died.

Researchers have been interested in studying why and how stressful childhood experiences affect sexual maturation, behavior, and reproductive outcomes. Girls who grow up without a father may start reproducing earlier, as the absence is an indication of environmental influences and insecurity in which a fast life history strategy is favored. Alternatively, the trend could be the result of genetic factors.

Researchers Markus Valge and colleagues wanted to investigate whether the absence of the father, the mother, or both is most strongly associated with the early onset of puberty in girls. Researchers used a large dataset to study girls born in Estonia between 1936 and 1962. Valge and colleagues had access to information about girls’ puberty rates (about breast development stages), when they had their first child, and their overall reproductive success (how many children they had in their lifetime). The girls either grew up in orphanages, without a mother, or because of divorce or death without a father.

After analyzing the data, the researchers found that girls whose fathers divorced began reproducing about 9.2 months earlier than girls who grew up with only their father or both parents, and about 7.4 months earlier than Girls whose fathers died. However, the difference in reproductive age was not significant once education was controlled for.

On average, girls whose mothers died had 0.25 fewer children in their lifetime than girls who grew up with only a mother or father. There was no difference in the number of children girls had after their father’s death compared to girls raised in an orphanage.

This study shows that stressful childhood environments do not predict faster sexual maturation for girls when it comes to education. Valge and colleagues argue that this may be due to low power and confounding variables. However, there was a correlation between girls’ ages at the birth of their first child and whether their parents were divorced. Valge and colleagues argue that this could be explained by Flinn’s hypothesis, which suggests that fathers protect their daughters from predatory males in order for girls with fathers in their lives to reproduce later in life.

This hypothesis is only partially supported, however, since girls whose fathers were dead did not have children significantly earlier than girls whose fathers were present. Valge and colleagues argue that the grandmother hypothesis (where mothers help promote the survival of their grandchildren) is supported given that girls whose mothers died had, on average, 0.25 fewer children.

A limitation of this study is that there was no information on whether a stepparent was involved in the families where mothers and fathers were absent. There was also no information about the age of the girls at the time of the death or divorce of a parent.

The study “Pubertal maturation is independent of family structure, but daughters of divorced (but not dead) fathers start reproducing earlier” was authored by Markus Valge, Richard Meitern and Peeter Hõrak.

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