Final answer:
Approximately 78 percent of ethnographically known societies accept polygyny, but the actual practice involves a small fraction of men, often under 35 percent. Urbanization tends to reduce polygyny due to influences like media and education. Polyandry is rare, forming about 1 percent of global cultural practices, and is often adapted to manage resources and control population growth.
Step-by-step explanation:
The fraction of ethnographically known societies that show some form of polygynous marriages is significant. In a majority of cultures (78 percent), polygamy, and specifically polygyny, is accepted. Although polygyny is widely accepted, the actual practice of it varies and tends to be limited to a small percentage of the population—often fewer than 10 percent and typically no more than 25-35 percent of men in polygamous cultures have more than one wife. These husbands are often older, wealthy, high-status men. The average plural marriage involves no more than three wives. For example, Negev Bedouin men in Israel commonly have two wives but may have up to four. It is also observed that with the advent of urbanization and its associated factors such as increased access to mass media, technology, and education, the prevalence of polygyny tends to decrease.
In Thailand, as many as one in four Thai men between the ages of 30 and 50 may have a second wife. This shows a current trend where polygyny is still practiced, often as an economic strategy that offers potential benefits to all family members. However, this practice can also lead to internal family conflicts and encompasses gender politics that frequently limit women's choices.
Contrastingly, polyandry, where a woman is married to more than one man at the same time, is extremely rare, accounting for about 1 percent of the world's cultures. In certain cases, polyandry functions as a strategy to minimize population growth and manage resources effectively in some communities such as in Nepal where fraternal polyandry is practiced.