*a series discussing the negative affects of White imperialism on BIPOC's access and education to non-monogamy.
"Submission to this law [monogamy] is the severest test to which a savage can be subjected. When we see a man, for conscience’ sake, parting with one or more favourite wives, can we deny him the credit of sincerity?"
Robert Moffat on Missionaries in Southern Africa, 1842
BIPOC are still picking up the pieces from racist colonization's effect on their relationships. It can be difficult for non-monogamous Black people to feel comfortable seeing rhetoric and educational spaces surrounding polygamy / polyamory controlled by White bodies in popular culture. Most of our White counterparts ignore or are ignorant of how colonization and enslavement of Africans deeply affected our relationship to non-monogamy.
Africans were practicing polygyny AND polyandry before the slave trade and colonization. Enslaved Africans even attempted to continue the practice in America and the Caribbean.
Uncivilized?
Upon the arrival of Christian colonizers, also came also their missionaries. Polygamy was a big issue to the European missionaries, as most of them found it incompatible to the Christian faith they were trying to convert Africans to. Furthermore, they felt it was uncivilized and savage, and in turn would not baptize polygamists in their new faith if they wanted to convert, expecting them to divorce "extra" spouses.
Polygynous husbands were urged to divorce their spouses and keep a single wife. For obvious reasons, this would eventually leave many women and children homeless and without resources. It should also be noted that missionaries were supported by their country's government - oftentimes the tactics to ensure conversion were dehumanizing.
It was assumed that their wives were essentially slaves and did not know any better. The colonizers also assumed African women and men were in these types of relationships due to sexual desires - furthering the hyper-sexualization of Black bodies. This stereotype had already followed Africans through the forced diaspora in America and enforced the Mandingo / Black Buck and Jezebel stereotypes of Black people well before the names had been coined.
Read Behind the Stats
There are studies covering literacy being lower amongst polygamous locations versus monogamous locations. some of theses studies also cover women and girls access to education and resources where polygamy is more acceptable. It is important to make note that some traditional Africans would not allow their children to attend the missionary schools since polygamy, as well as other traditions, were being taught against during this time.
Furthermore, with violent colonization, marginalization of Africans wanting to keep their traditions, not recognizing polygamous marriages (although many countries in Africa do now), and limiting resources / punishing those who opposed...
...it is not a surprise those studies would yield those results in the past few decades.