Professor Bruce J. Ellis, the John and Doris Norton Endowed Chair in Fathers, Parenting and Families at the UA Norton School of Family and Consumer Sciences, and Jacqueline M. Tither at the University of Canterbury in Christchurch, New Zealand, have just published their study in the journal Developmental Psychology.

Ellis and Tither's study sought to unravel several competing theories about how this happens.

Those theories vary from whether dysfunctional families and absent fathers are the cause of early puberty, or underlying environmental factors that cause family stress, such as poverty, or whether there might be a genetic link.

Understanding what triggers early puberty could give health care officials an advantage in dealing with issues that sometimes accompany it. Early puberty is often cited as a risk factor for young women, linking them to early pregnancy and an array of health problems, such as breast cancer.

Ellis and Tither interviewed sisters in the same family who differed in age. The sample included 90 intact families and 70 families where the parents had divorced. Questions centered around family composition, who the girls were growing up with and when, the nature of the father's involvement and paternal warmth.

“Our goal was to test for the causal effect of family environments and particularly the father's role in the family on a daughter's age of puberty,” Ellis said. “We looked at families in which one daughter might be five and the other 12 when a divorce occurred. So the youngest daughter had seven more years living in a disrupted family without her father, compared to her older sister. Our study showed that more exposure to father absence was linked to earlier puberty.”

Ellis said lots of research over the years, including his own, has documented the effect, but left a basic unanswered question.

“That is, there has always been a basic alternative explanation for this finding. The theory that we're working from suggests that something about children's experiences in their families, and particularly about the presence of different members of the families in the home, actually alters the reproductive axis and timing of puberty,” Ellis said.

“The idea is that children adjust their development to match the environments in which they live,” Ellis said. “In the world in which humans evolved, dangerous or unstable home environments meant a shorter lifespan, and going into puberty earlier in this context increased chances of surviving, reproducing and passing on your genes.”

Ellis said an alternative explanation suggests the whole thing is spurious, that it may not be that growing up without a father causes early puberty in girls. It may be some third variable out there causes both family disruption and early puberty. And that could be genetic in origin.

“We know that father absence and early puberty go together. But we don't know why and we don't know how. This study was meant to figure out that issue. The importance of this research was to show that the link is real: exposure to fathers can actually alter their daughters' sexual development.”

Ellis noted that divorced families can have other factors that stress its members, such as alcoholism, drug use, depression, family violence or criminal activity. More important than the absence of a father are the characteristics of the father and what he did. “It's not enough to simply have a cardboard cut-out of a father sitting on the couch. What the father does is critical,” said Ellis.

Ellis said the most dramatic finding of the study was that in divorced families with a father who had a history of socially deviant behavior, that the younger sisters who had less exposure to their fathers tended to go through puberty nearly a year earlier than their older sisters. They also went through puberty nearly a year earlier than other younger sisters who were not exposed to dysfunctional fathers.

“We found that girls with very high levels of exposure to stress early in life, who then had that stressor removed, tended to go through quite early puberty,” he said. “This actually concurs with international adoption studies showing that girls from third-world countries who had a lot of stress in early childhood and were adopted into Western societies tend to have very high rates of early puberty. It is consistent with there being a sensitive period for changes in stresses and life situations. And that could be relevant for parents.”

Ellis and Tither’s research was supported by a grant from Fathering the Future Trust, Christchurch, New Zealand.

Contact: Bruce J. Ellis, 520-626-5703, bjellis@email.arizona.edu