The University of Texas estimates that 32 out of every 1,000 people in this world are a twin or 16 pairs in 1,000, which translates to 3 percent of the population. This figure appears to vary by region, race and ethnicity. Certain ethnic groups produce more twins than usual. Others produce less.
While researchers agree that identical twins happen by sheer chance, having fraternal twins is hereditary. If someone else in your family had fraternal twins, then you are more likely to give birth to fraternal twins. If a mother herself is a fraternal twin, the chance of conceiving twins increases four-fold. These factors cause twins to usually run in families and in certain ethnic groups as a whole. In fact, race and ethnicity seems to play a major role in twinning. For instance, in the U.S., twins are most common among African-Americans (36.8 per 1000) and least common in Hispanic/Latino Americans (21.8 per 1000).
A pair of twin girls in the “twin town” of Kodinhi, India. Photo credit
The highest rate of twin births has been observed to occur among the Yoruba community in southeast Nigeria centered around a sleepy farming town called Igbo-Ora. As many as 45 to 50 sets of twins are born here per 1000 live births. In other words, nearly 10% of the population are twins. The unusually large number of twin births in the region have earned the town the nickname of “Twin Capital of the World.”
While nobody has been able to prove medically, research has suggested that the multiple births could be related to the eating habits of the women in the region. It is possible that the high consumption of a specific type of yam containing a natural chemical may stimulate the ovaries to release an egg from each side. But then, the large number of twins being born here could also be a simple matter of genetics.
Either way, for this predominantly rural community, it doesn’t matter. Multiple births are celebrated here and have, over the generations, been regarded as a blessing from God. Many pregnant women in Igbo-Ora wish for multiple births.
Igbo-Ora is not the only town where you’ll find skewed twins birth rate. In Brazil’s Candido Godoi city, near the Argentine border, a similar twin phenomenon occurs.
The rate of twin births in Candido Godoi is 10%, significantly higher than the overall 1.8% rate for the state of Rio Grande do Sul and the national twinning rate. The twin births were noted from the early twentieth century, when the first colonists included seventeen sets of twins, and have been observed through several generations since. The population is largely of Polish or German ancestry, with many tracing ancestry to the Hunsrück region of Germany, which has a higher than average twinning rate.
For decades researchers struggled to explain the high concentration of twins. Then in 2009, Argentine historian Jorge Camarasa proposed an outlandish theory in his book Mengele: The Angel of Death in South America.
Josef Mengele was a notorious Nazi doctor who conducted gruesome twin experiments with twins in the German concentration camp in Auschwitz. His task was to carry out experiments to discover the secret behind twin births so that his master, Adolf Hitler, could use it to artificially increase the Aryan population. As the Allies started closing in on the Nazi German regime, Mengele is fled to South America. Jorge Camarasa suggested that Mengele continued to conduct experiments on women while on the run in South America, disguising himself as a roaming physician and veterinarian. Presumably, Mengele had successfully cracked the twin code leading to the increase in the town population.
Such speculation has been disputed by local historians who says Mengele did not study twins during his time in Brazil, and the high frequency of twins predates Mengele's arrival to South America. Researchers have also found a genetic linkage and possibly inbreeding as the most likely explanation for the high frequency of twins.
Ten-year-old Kitana and Tahuana Schmitt are just one of some 700 twins in the town of 6,600 residents. Photo credit
Neslson and Norberto Riske, two older residents of Candido Godoi. Photo credit
17-year-old Mariara and Maira Kotowski, of Candido Godoi. Photo credit
Another town that wishes to declare itself the “Town of Twins” is Buzim, in northwest Bosnia. This town of 20,000 is home to more than 200 sets of twins. Unlike Igbo-Ora and Candido Godoi, the residents to Buzim wants to use the town’s extraordinary twinning rate and turn it into a tourist attraction.
According to Reuters, the phenomenon was first discovered by local journalist Nedzib Vucelj when his wife gave birth to twins during the 1992-95 civil war. Vucelj learned that at least 21 sets of twins had been born in the town during the same period which struck him as unusual. So he launched a Facebook page to try and discover other twins from the town. So far, he has identified at least 200 sets of twins.
Buzim is mainly a patriarchal community with a tradition of large families and possible inbreeding, which may have helped such genes to persist.
Twins of Buzim. Photo credit
In the east, the twin phenomenon is seen in the village of Kodinhi in the state of Kerala, in India, where there are 250 sets of twins officially registered. This is a village of just 2,000 families. In 2008 alone 15 pairs of twins were born in the village out of 300 healthy deliveries and the twinning rate has been increasing year-on-year. In the last five years alone (before 2009) up to 60 pairs of twins have been born. The twinning rate is even more remarkable when you consider that the Indian subcontinent has one of the lowest twin birth rate.
Twins pose for photograph in the village of Kodinhi, India. Photo credit
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