Reproduced with kind permission from the Sydney Morning Herald
Author: Bettina Arndt
Date: 09 Mar 2002
Publication: Sydney Morning Herald
`Strange males’ can speed up the path to maturity.
The large numbers of children growing up with stepfathers may be contributing to the worldwide trend towards girls reaching early puberty.
According to research from a landmark American study on divorce and children, life in divorced or remarried families promotes early maturation and increases the likelihood of early pregnancy.
The figures are striking girls living in step-families are almost twice as likely to reach early puberty as girls from non-divorced homes. While only 18per cent of girls from intact homes started menstruating by 11 or younger, this applied to 25 per cent of girls in divorce homes and 35per cent in step-families.
On average, girls in stepfather families menstruated nine months earlier and in divorced homes four months earlier than girls from intact homes.
The American study, involving nearly three decades of research covering 1400 families, has just been published in For Better or For Worse, a book on the impact of divorce written by the principle researcher, psychologist Mavis Hetherington, with her co-author, John Kelly.
The authors propose two explanations, based on the theories of evolutionary psychologists, to account for the accelerated puberty in divorced and blended families.
First, early puberty may be a response to life in a hostile environment namely the high rate of conflict and stress associated with divorce and remarriage.
The alternate theory focuses on the fact that in many animal species, the presence of a strange male is an environmental cue that induces sexual readiness in young females. Hence early menarche may be triggered by the presence of a “strange male” in the household.
There is considerable international evidence suggesting girls may be maturing earlier, including Marcia Herman-Gidden’s 1997 study of 17,000 American girls and a British study at Bristol University which tracked 14,000 children and found one in six girls with signs of puberty by eight years old, compared to one in 100 a generation ago. There is, as yet, no comprehensive Australian data on onset of puberty.
Explanations have included hereditary and diet factors, increases in obesity and body weight, chemicals acting as endocrine disrupters and the sexualisation of children by the media. Now the “strange male” theory must be added to the list.
Dr Bruce Ellis, now at the University of Canterbury in Christchurch, has been involved in a series of studies exploring early puberty and family structure, firstly in the US and now in New Zealand. His American work examined the family circumstances of girls in kindergarten and tracked them through to puberty.
His results reveal that the presence of the stepfather, or unrelated adult male in the household, can lead to early puberty maturation in girls. “And the earlier and longer the exposure, the stronger the effect,” said Dr Ellis.
The critical time for that exposure seems to be the first five to seven years of life, when the pathways to puberty are set down. Dr Ellis speculates that an environmentally triggered process shunts the girl towards a particular reproductive strategy. This process may be influenced by male pheromones chemical substances secreted by the body with the pheromones of unrelated males apparently accelerating puberty development, whilst the scent of the biological father may delay maturation.
Animal studies demonstrate that pheromones can trigger early maturation. “If you take a prepubescent female mouse and have her sleep in a cage where an unrelated adult male has been, exposure to the litter saturated with his pheromones results in the female reaching puberty faster,” says Dr Ellis, explaining that there has been similar results with cows and pigs.
Dr Ellis says that with children tending to receive higher quality parental investment in intact families, it makes sense to prolong that investment by maturing more slowly.
His research also indicates that puberty is delayed by the presence of the biological father, particularly fathers who interact more with their daughters when they are young. Here too there is parallel animal research.
“Female prairie dogs who grow up in the same den with their male sires tend to go through later puberty than young females who are not kept in the same den with their biological fathers. This may also be a pheromonal effect,” he says.
Research has consistently shown that girls from divorced families are sexually active at a younger age, have a greater number of partners and are at greater risk of early pregnancy.
Adolescent psychologist Michael Carr-Greg is intrigued by the Hetherington/Ellis research.
“It does gel with what I have observed in families. I think it has huge implications,” Dr CarrGregg says.
While there is no comprehensive Australian data, Dr Carr-Gregg suspects Australia is seeing more early maturers, who often struggle because they lack the emotional maturity to cope with the male attention they receive as a result of their appearance. He suggests that in step-families “the adult male may find it extremely difficult to deal with her precocious sexuality and this adds to strife between the remarried couple”.
Dr Ellis’s research shows no impact on the timing of puberty from stressful relationships in intact families, but finds that conflict between parents in the step-family does contribute to early maturation.
Dr Ellis is seeking possible genetic explanations for the patterns emerging in families. Research examining mother’s timing of puberty and age at first childbirth has suggested that both genetics and family relationships are relevant, yet he says inherited characteristics from fathers require investigation.
He acknowledges that the stepfather factor could now be a significant part of the story. “With the strong increases in the numbers of children growing up in families where they are exposed to pheromones of unrelated adult males, it certainly could be having an effect,” Dr Ellis says.
For David Blankenhorn, author of Fatherless America, the message from the Ellis/Hetherington data is clear: “If we want young girls to delay sex and childbearing, having a loving biological father on the premises is a good idea, while having unrelated men on the premises is not.”
Owen Pershouse is a Brisbane clinical psychologist and founder of MENDS, an organisation supporting separated men.
Mr Pershouse believes this research should influence decisions about contact between children and their biological fathers after divorce “particularly at critical developmental stages”.
Dr Ellis says that given the uncertainty about the genetic component it is too early to use these findings as the basis for social policy, but Mr Pershouse warns that they will only add to the angst felt by many separated males regarding daughters who are left behind with their mothers, particularly in households that involve either a new boyfriend or stepfather.
“We often find ourselves counselling divorced men who watch helplessly knowing their children are being damaged in such family situations,” he says. “And here we have new evidence suggesting girls may face another hazard.”