(PhysOrg.com) -- Researchers have found that men with strong masculine traits are likely to produce similarly macho sons but, according to the new study by the University of St Andrews, macho sons are not considered especially attractive.
In a study of family photographs, psychologists Professor David Perrett and Elisabeth Cornwell (now at University of Colorado at Colorado Springs) found that while both father and mother can influence the attractiveness of their daughters, a woman's looks do not impact on the attractiveness of her son as an adult.
Professor Perrett said, "Family photographs present a valuable resource in studies of mate choice and the extent that traits pass across generations. In our new study we demonstrated how this resource can be tapped to provide some evidence on how evolutionary theory applies to human mate choice.
"One interpretation of sexual selection which is a major driving force for evolution is that mate choice is all about choosing the most attractive partner in order to produce attractive offspring. Success in biological terms is about producing offspring, and if offspring are attractive when adult they have the best chance of parenting a new generation," he explained.
Some theories suggest that a female can increase her own reproductive success by choosing 'sexy' mates, whose genes are passed onto male offspring, making them attractive and irresistible to the next generation of females. The hypothesis presumes that masculinity underlies male allure. Contrary to these predictions, St Andrews' researchers found that attractive fathers and mothers do not necessarily produce facially attractive sons.
"We checked to see if male and female facial traits are inherited. For the male line, we find that facial masculinity conforms to the rule 'like father like son': masculine dads have masculine sons, but we did not find any evidence that facial attractiveness is passed from father to son.
"We are perplexed as to why we did not find any evidence for the inheritance of attractiveness in males, through either the female or male parent. The answer may be because women vary considerably on the extent to which they find masculinity attractive. We know that attractive feminine women show a strong preference for masculine male faces for long-term partners," Professor Perrett explained.
The researchers studied the family photo albums of students, collecting images of over 100 females and 100 males and their respective biological parents taken over several years. The test methods were very simple - photos of each student, father and mother were rated separately for attractiveness, and for femininity/masculinity. The team then compared how the ratings of parents related to their offspring.
"When we looked at women¿s faces, we found clear evidence that attractiveness passed from both father and mother to daughter. Attractive fathers were more likely to produce attractive, feminine daughters, whether the mother was attractive or not.
"Until now, stress has been placed on the female selection of males, but in many species, including humans, both sexes invest time and effort in offspring and are choosey about their partner. The notion that selection is all about producing sexy sons ignores male selection of females and ignores the importance of attractive traits passing down the female line. Our research redresses the balance, and demonstrates effects of mate choice on female looks," said Professor Perrett.
There is one more piece of the puzzle that the St Andrews' researchers hope to address in future: are parents' preferences inherited by their offspring?
Provided by University of St Andrews
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