There's a village where twins are remarkably common, and the theories why are fascinating.

For years so many twins were born in the southern Brazilian village of Cândido Godói, the residents wondered whether there was something in the water.

The birth rate of twins in Cândido Godói is 10 per cent, significantly higher than the global average of 0.4 per cent.

Over the years many theories have been put forward for why this phenomena was occurring – the most popular of which was that Josef Mengele, the Nazi physician known as the Angel of Death, conducted experiments on the women there.

Mengele was a Nazi doctor who conducted twin "studies" in Germany and experiments with twins in Auschwitz, and he was known to have fled to South America as the Allies were closing in on the Nazi German regime.

The Argentine historian Jorge Camarasa suggested that Mengele conducted experiments on women in the area, which could be responsible for the high ratio of twins. Apparently around the time of Mengele's arrival in southern Brazil in 1963, the incidence of twins began to increase, leading to the current rate of twinning of 1 in 10, over half of whom are fraternal twins.

However in 2011, a group of scientists told The New York Times, that they could now rule out that possibility.

Ursula Matte, a geneticist in Porto Alegre, Brazil, said a series of DNA tests conducted on about 30 families since 2009 found that a specific gene in the population of Cândido Godói appears more frequently in mothers of twins than in those without. The phenomenon is compounded by a high level of inbreeding among the population, which is composed almost entirely of German-speaking immigrants.

“We analyzed six genes and found one gene that confirms, in this population, a predisposition to the birth of twins,” Matte said.

The study led by Matte also analysed 6,615 baptism certificates dating back 80 years in the predominantly Roman Catholic town and found that the twins phenomenon existed in the 1930s, “long before Mengele’s period".

“In the initial stages of our research we immediately disproved any involvement with Mengele,” Matte said.

Matte's team of researchers also analysed the town's water supply and uncovered no abnormalities.

While studying the baptism certificates, the scientists confirmed that the highest concentration of twins has been in São Pedro, with 33 pairs out of 436 births from 1959 to 2008, all living in a one-and-a-half-square-mile area.

The scientists believe that a small number of immigrant families living in São Pedro may have brought the variant gene to the region.

Two sets of twins in two years on I Don't Know How She Does It. Post continues...

“This does not mean that it is a universal gene,” Dr. Matte said. “If I take twins from New Zealand and test them, it will probably generate a different result.”

However, rumours about the village and its mysterious history continue to this day.