According to Mark Dyble, the dawn of agriculture gave rise to the practice of polygamy.
Polygamy is having many spouses. It usually is a man having many wives.
The society before was an egalitarian society. This is a society for a gatherer-hunter community. This society treats everyone as equal.
When they began to find land and settle down to farm the land, men no longer wanted to become equal. They wanted to acquire more possession. They wanted to have more wives and more children. Thus, polygamy practices arise.
This all depends on what you are going to be writing or speaking about. If you told me, I would be glad to help.
