The birth of twins has long been considered a weird and wonderful occurrence. Twins can either be Identical (monozygotic), or Non-identical (Dizygotic). Monozygotic twins are created when one egg becomes fertilised and then splits in two, producing two identical zygotes. Dizygotic twins are created when two eggs are fertilised and they both implant in the womb, producing two non-identical zygotes1,2.
Yoruba is a major ethnic group in Nigeria, dominant in the southwestern part of the country. Yoruba people can also be found in Togo, Benin and Ghana. There is a town called Igbo Ora in the southwestern part of Nigeria, which has a lot of twins3. The town proudly advertises this with a banner welcoming people to the ‘Home of Twins’, as seen in figure 14. Akinboro and colleagues carried out a study in states of Nigeria dominated by Yoruba people (Oyo and Ekiti) showed a very high incidence of twin birth of about 40per 1000 deliveries5. Although this number could be higher, because data can be limited by lack of documentation, and women in rural areas having home births that go undocumented. This article is going to focus on the Yorubas, having a high incidence of twins. Why is there a high twin birthrate in the Yoruba ethnic group?
Figure 1: Welcome to the nation’s home of twins.
Africa has a higher rate of twins compared to the rest of the world. Nigeria was recognized as “The twin Champion of The World “1. Kehinde and Taiwo are the special names given by Yorubas to twins. Taiwo is for the older twin and Kehinde is for the younger twin. Idowu is the name given to the child that is born after a twin. Mama Ibeji and Papa Ibeji which means mother of twin and father of twin respectively is the name given to parents. Research1 shows Africans to have more twin births than other parts of the world. Benin, which has a high Yoruba population, had the highest number of twin births.
It is a very popular belief in Nigeria that the high rate of twins born is due to the high consumption of yams. Yams are a staple food in Africa, eaten in most households. The Yoruba people have a lot of yam and yam derived foods in their diet6. Yam is known to increase estrogen level7. So, it could be argued that diet may be a major factor contributing to the high twin births within Yoruba families. The limitation to this argument is that other ethnic groups within Nigeria also consume yam, but don’t come close to the rates of twin births compared to the Yoruba people. Locals of the Igbo Ora town claim that their high rate of twins is because of a special leaf delicacy called Okro (Abelmoschus esculentus) that they eat8. Other factors known to affect twin births include genetics, age, weight, height, and previous pregnancies9.
Therefore, although there is a very high rate of twins in Yoruba families, there is no scientific proof of a direct link between their diet and the birth of twins. But there haven’t been any studies completely debunking those claims and beliefs either. With it being such a weird and wonderful occurrence, further research to understand the exact reasons for the births of so many twins would be fascinating. These discoveries could become a big milestone in reproductive science and engineering and could indicate towards a solution to infertility and other aspects of reproductive science.
References
1. Monden C, Pison G, Smits J. Twin Peaks: more twinning in humans than ever before. Hum Reprod. 2021;36(6):1666-1673. doi:10.1093/humrep/deab029
2. Bulmer MG. The Biology of Twinning in Man. Clarendon; 1970.
3. Choi CQ. Countries With Most Twins Identified. livescience.com. Published October 11, 2011. Accessed March 21, 2022. https://www.livescience.com/16469-twins-countries-twinning-rates.html
4. Acheson C. Seeing Double in Nigeria’s Igbo Ora. pan-African. Published February 26, 2021. Accessed March 25, 2022. https://pan-african.net/seeing-double-in-nigerias-igbo-ora/
5. Bakare A, Akinboro A, Azeez M. Frequency of twinning in southwest Nigeria. Indian J Hum Genet. 2008;14(2):41. doi:10.4103/0971-6866.44104
6. Cunningham A. Yams and Twins: Is There Any Truth To This Myth? Zoom Baby. Published October 25, 2020. Accessed March 21, 2022. https://www.zoombaby.co.uk/can-yams-really-help-to-boost-female-fertility/
7. Wu WH, Liu LY, Chung CJ, Jou HJ, Wang TA. Estrogenic Effect of Yam Ingestion in Healthy Postmenopausal Women. J Am Coll Nutr. 2005;24(4):235-243. doi:10.1080/07315724.2005.10719470
8. Akwagyiram A. Nigeria’s twin town ponders cause of multiple births. Reuters. https://www.reuters.com/article/us-nigeria-twins-idUSKCN1RL1A9. Published April 9, 2019. Accessed February 12, 2022.
9. Marcin A. What Are the Chances of Having Twins and Can You Increase Them? Healthline. Published December 15, 2020. Accessed February 13, 2022. https://www.healthline.com/health/pregnancy/chances-of-having-twins