Gebremedhin, Samson. 2015. “Multiple Births in Sub-Saharan Africa: Epidemiology, Postnatal Survival, and Growth Pattern.” Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies 18 (1): 100–107.
The rate of multiple births in Sub-Saharan Africa is 1.7x that of European levels (h/t Emil Kirkegaard):
The multiple birth rate in SSA (17/1,000 births) appears to be higher compared to the level in other developing countries where the magnitude is unlikely to be affected by ART. A study reported that in many South and South-East Asian countries, including China, India, Indonesia, and Pakistan, the twinning rates remains below 10/1,000 births; likewise, the incidence in Latin American countries is similarly low (less than 9/1,000 births; Smits & Monden, 2011). The rate is also higher than the 1980s pre-ART multiple birth incidence in England and Wales (9.6/1,000 births) and several other West European countries (less than 10/1,000 births; Pison & D’Addato, 2006).
Multiple birth rates appear to vary substantially across the 25 countries included in the study. In general, the rate was higher in Central and West Africa countries and lower in Eastern and Southern Africa countries. The lowest (12/1,000 births) and highest (25/1,000 births) figures were reported in Ethiopia and Benin, respectively. The disparity can be likely due to genetic differences as variations in risk factors of multiple pregnancy (e.g., age and parity) across the countries are unlikely to be substantial.
One more piece of evidence for J. Philippe Rushton’s theory of a Negroid < Caucasoid < Mongoloid hierarchy in r/K life history strategies, as having bigger broods is more r-selected.
I noticed that twinning rates seem to be lower in the higher quality Sub-Saharan African countries, e.g. Kenya (highest on SACMEQ), Ethiopia (most impressive history/successful current development), Rwanda (Paul Kagame).
And Ethiopia being lowest here is perhaps not surprising, given them being evolutionarily closer to Eurasians than West Africans and historical admixture with Arabs.
Quick correlations between the twinning rate and other measures:
- HDI: 0.07
- IQ (Lynn 2012): 0.54
- IQ (Lynn 2012, but including countries without data given as neighbors’ average): 0.44
- SACMEQ (international standard test, like PISA): 0.61
Not rigorous by any means, but there’s probably something here.
|Twins (/1,000)||SACMEQ||IQ||IQ (proj)||HDI 2018|
|Sao Tome & Principe||21.7||67||0.589|