I'm not even sure what you are trying to say.
The implication being that the cultures of (some) people are unchanging and fixed. I think you'd agree with a statement like: Cultures and family values do change all the time, due to a variety of factors like better medical care, and economic empowerment, in reasonably predictable ways.
So it's not unchanging cultural differences between Africa and Europe that drive the different fertility rates, but rather different socio-economic factors that drive a different family culture. Changing the socio-economic factors will change the culture surrounding families, just as much in Africa as it did in Europe, the Middle East, Asia, etc... at various times in the last century and a half.
I'm sure an alien species or a computer simulation having a few of the same basic drives as humans do (sex is very pleasurable, contraception exists, raising educated children is extremely expensive and hard, state provides pensions in old age, people are free to have or not to have children, child mortality is low, work provides money, money satisfies needs, quality work is abundant only in high density cities and a coupe of others) will arrive at same fertility problem we have arriven at.
My second point was that there is nothing we can reasonably do without a major overhaul of human traits or shutting down the technological advanced world we live in.