Female Shortage Leads to Early Marriage for Females - and Why Polygyny Leads to Oppression of Women and Angry Men

This article from the journal of Evolutionary Psychology describes what tends to happen when there's a relative shortage of women compared to men.  The authors analyzed census data from 50 largest metropolitan areas in the United States and found that the relative shortage of women was correlated with:

1. lower average age of females at marriage
2. higher variation in the ages of males at marriage (no significant effect on average age at marriage)

The explanation is essentially this: when there is a shortage of women, women get wooed into marriage more aggressively and tend to marry at a younger age.  Another way of looking at it is that women are more likely to find a suitable mate at an earlier age.  Since young men know that there's increased competition for brides, they are also more likely to be willing to want to commit at a young age.  However, young men do not on average have the wealth and status of older men.  Some women may use the extra bargaining power that they have to marry an older guy with wealth and status.  Also, some young men may find themselves "unmarriageable" before building their careers.  All this combines to form a situation in which women tend to marry early but males vary a lot in the age at marriage.

Some amount of female shortage in a society that enforces monogamy (USA) is clearly beneficial for women, who can use their scarcity to land either a younger guy who otherwise wouldn't have committed or an older guy with wealth and status.  However, extreme female shortage caused by polygyny (one man can take on multiple wives) is bad for most women and most men.  In every society where polygyny is practiced, the average age of marriage is very low.  This is a uniform trend from ultra-orthodox Mormon communities, to Muslim societies, to many countries in Africa.  This makes complete sense: since some men take multiple wives, there's an extreme shortage of single women compared to men looking for brides.  Women get hit on aggressively and men are very willing to marry.  The age at marriage becomes so low that many women forego higher education.

The need to keep multiple wives in line while keeping aggressive single men at bay promote restriction of female freedom and strong patriarchy.  To varying degrees, women are restricted to the home and are forbidden from showing off their sexual appeal publicly (burqas are the extreme case, orthodox Mormons have a code of dress).  Look at the two pictures below.  Both types of dresses are designed to hide women's sexual appeal - it's difficult to judge the body contours of these women.  There's a huge variation in male reproductive success, and the winner males must try hard to keep their spoils to themselves.

The loser males, in particlar, become very frustrated.  In monogamous societies, virtually all males are guaranteed a wife if he wants one badly enough (just not as hot and high-status as he might hope).  There's overwhelming evidence that when men marry, they become calmer and more stable.  His testosterone goes down.  It is perhaps no coincidence that Muslim societies tend to produce suicide bombers.  They are men who are angry, frustrated, and have no family anyway.  In almost all civilizations, monogamy was the rule - exceptions were granted only for very powerful men such as kings - and even in those cases there was usually only one official wife.  All this was for a good reason, and I am lost as to why Muslim societies developed the way they did.  Perhaps the promise of virgins girls in heaven kept lower status Muslim men from revolting?