Mary was probably 12 or 13 when she was Betrothed to Joseph
According to Jewish tradition (I am told), in the first century girls were betrothed when they were 12 years old, and married a year later at 13. Many people are uncomfortable with this young age, and place Mary’s age of betrothal at 14 or even as old as 18. If you look at most pictoral representations of Mary with the baby Jesus, however, she looks to be anywhere from 20 to 30.
This post has a simple thesis: there is nothing universal, binding, eternal, or sacred about the “appropriate” age to willingly commence sexual activity. This statement is not a justification for pedophilia or child sexual abuse. I am highlighting, however, the social relativity of age-appropriate sexuality in general, and age-appropriate coupling in particular.
Our feelings, on the other hand, about age appropriate sexuality seem like they are objectively true. The process of socialization, which begins at childbirth, is such that socialization feels binding, as “natural” as breathing. This is why culture and society seem so inescapable. For survival and social solidarity, we learn what is safe and what is dangerous. That’s why socialization is supposed to be “second nature”: it helps our species survive.
Note: in focusing on the social construction of adolescence, I am not urging that sexual activity start at earlier ages. I am not disregarding the fact that having children interferes with getting an education and becoming a valuable profit center for industry and commerce. I am simply saying that there is nothing objective about what we feel is an appropriate age to commence sexual activity or to marry.
Age of Consent: Today and Yesterday
In sixteenth through eighteenth century Europe, many countries set the legal age of marriage was set between 10 and 12 years old. In 1689 Virginia, Mary Hathaway is recorded as marrying William Williams at age 9.
Today, 14 is the lowest official age of consent for females in Bolivia, Columbia, and Paraguay. The age of consent is 15 in Denmark, Estonia, Georgia, Lithuania, Slovenia, Canada, and Mexico, as well as in Angola, Mali, Niger, South Africa, Tanzania, Iraq, Jordan, Kuwait, Palestinian Territories, the Philippines, Syria, and Venezuela. Of course these ages can be difficult to enforce in outlying regions beyond the control of the national governments. A number of governments also allow marriage after puberty, with the approval of parents or the courts. In the Sudan, puberty in the legal moment of marriageability (See “Age of Consent“).
Adolescence as a Social Construct
In the social sciences there is almost universal agreement that the concept of “adolescence” is not biologically determined, but socially determined, prompted by the demands of industrialization. Many of you are familiar with this information, but for the rest I provide a small sampling of this concept in contemporary scholarship.
- “The emergence of adolescence as a distinct social group is the result of the many changes that occurred in society as a result of the Industrial Revolution. These changes included industrialization, urbanization, immigration, and institutionalization of virtually every aspect of [society].” 
- “The only real problem is the social construction of adolescence that has imposed upon men and women the burden of being teenagers.”  (click here)
- “[T]he origin of our current concept of adolescence . . . relates the social construction of adolescence. ̄ Adolescence as a concept was the “result of industrialization.” 
- Quite simply, childhood and adolescence are socially constructed phenomena.
- With industrialization and urbanization, the structure of families began to change.
- [A] moral panic occurs “when the official or press reaction to a deviant social or cultural phenomenon is ‘out of all proportion’ to the actual threat”. 
- LeTendre builds “on historical studies of the social construction of childhood and adolescence, . . . [discussing] the broad social forces of mass industrialization and mass schooling. 
- It was in the period after World War II . . . that [witnessed] the focus on adolescence as a social construction [and the] problems of sexual expression as the critical factor in creating an adolescent trauma.” Many people “indict industrialization.” 
- [T]he concept of adolescence came into existence during the last two decades of the 19th century: . . . Basically, [prompted by] industrialization . . . . 
- [C]hildren are theorized in research [which] characterizes childhood as a socially constructed category . . . . Adolescence as a phenomenon emerged after industrialization and an elongated span of compulsory schooling . . . . 
It is accurate to say that in an industrialized country, where education and maturity are extremely important, a high age of consent and legal marriage is important for reasons which are neither natural nor universal.
When we consider our feelings about May-December marriages and cradle robbing, about pederasty and sugar daddies, our feelings about age disparity in sexual relationships come into play. What we have seen and feels familiar will feel safe, while what we have not seen will feel alien and strange, dangerous. And there is nothing absolute about those feelings, except for the feeling, depending on the person, that those feelings are absolutely correct.
 Elton, M. The Social Construction of Adolescence, scribd, 2010.
 Rocha, Sam. “Sex Miseducation: Abstinence Doesn’t Make Sense”, 2013.
 Stern, David, and Dorothy Eichorn, eds. Adolescence and Work: Influences of Social Structure, Labor Markets, and Culture, Routledge, 2013.
 Valdivia, Angharad N. A Companion to Media Studies, Wiley, 2008, p. 229.
 LeTendre, Gerald K. Learning to be Adolescent: Growing Up in U.S. and Japanese Middle Schools, Yale University Press, 2000.
 Ianni, Francis. Search for Structure, Free Press, 1998, p 10.
 Mason, Laura Deane, School Facility Design Characteristics Supporting California Schools to Watch–Taking Center Stage Middle Schools: Perceptions of Middle School Principles and Teachers, University of LaVerne, 2008, p 48.
 DeLamater, John D., and Amanda Ward, Handbook of Social Psychology, p 124, Springer, 2013.