Developed society = the parts of the world where people aren't having kids, and therfore aren't passing on their culture and values effectively.
Backwards polygamous society = the parts of the world helping the developed societies maintain positive population growth to prop up their ponzi retirement and fractional reserve banking systems. Growing rapidly as a percentage of those societies and converting them to their values through numbers and democracy.
Result - polygamy, which has been the norm in human history and is a driving force behind ensuring the fittest breed, will return.