for National Geographic News
Did Nazi doctor Josef Mengele carry on his sadistic science decades after World War II?
Recent reports have held up a remote Brazilian town—filled with blonde, blue-eyed twins—as evidence of Mengele's postwar attempts to add to the ranks of an Aryan "master race."
But research announced today says Cândido Godói's "Nazi twins" are nothing more than a myth.
The outback town of about 7,000 has a twin rate nearly 1,000 percent higher than the global average.
The twins' fair features are no mystery—Cândido Godói (map) is largely populated by the descendents of German immigrants. But the frequency of twin births is a decades-old mystery.
Earlier this year Argentine historian Jorge Camarasa offered a bombshell of an explanation in his book Mengele: The Angel of Death in South America.
In World War II, Mengele, aka the Angel of Death, was mainly interested in twin research while serving as chief doctor at the Birkenau extermination camp in Poland.
According to Camarasa, Mengele likely continued his twin experiments in the 1960s while on the run in South America.
Mengele disguised himself as a roaming physician and veterinarian and gave pregnant women in Cândido Godói an ahead-of-its-time, twin-inducing mix of drugs or hormones, the historian suggests.
Video: The Twins of Cândido Godói
Camarasa cites interviews with locals who say they remember the visits of a traveling German doctor who provided mysterious potions or drugs.
The locals recalled him by different names, Camarasa explained. But each interviewee had the same reaction when shown a picture of Mengele: "That's him."
Mengele was in fact in Brazil during much of his South American exile, which began in 1949 and ended in 1979, when he died of a stroke while living under an assumed name.
During the war, Mengele and colleagues had used Jewish prisoners in often deadly fertility experiments. The ultimate aim: to provide more Aryans to populate Hitler's "Thousand Year Reich."
(Related: "'Hitler's Stealth Fighter' Re-created.")
Twin Boom Predates Nazi's Exile
The twins of Cândido Godói—most of them fraternal, or nonidentical—are eager to shake their supposed Nazi connection.
"Because of these rumors that Mengele was there, the population gets very upset about it," said geneticist Lavinia Schuler-Faccini of Brazil's Universidade Federal do Rio Grande do Sul. "So some leaders of the community asked the university to start a project to try and understand why this place has such a high incidence of twin births."
The resulting research, led by Schuler-Faccini and backed by the Brazilian government, is featured in a new documentary: Explorer: Nazi Mystery—Twins From Brazil, which airs Sunday, November 29, at 9 p.m. ET/PT on the National Geographic Channel. (The National Geographic Society owns National Geographic News and part-owns the National Geographic Channel.)
Video: The Researchers at Work
For the initial phase of their study—which has not yet been published or reviewed by outside scientists—the team combed through baptismal records, which the researchers say should cover about 75 percent of the children born in predominantly Catholic Cândido Godói. The records would reveal where and when the town's many twin births had occurred.
The town's baptismal records date back to 1927, long before Mengele's supposed arrival—and so does the exceptional rate of twinning, the team discovered.
Furthermore, the records show no "surge" in twinning in the 1960s, when Mengele is said to have experimented on the local populace, the study says.
Also, the high rate of twin births continues today, which rules out a role for Mengele, the researchers say.
Had Mengele injected mothers with something to alter their pregnancies, the twin rate should have dropped off when his supposed work stopped.
"Even if Mengele had ovulation induction drugs available, they would have had an effect only on the immediate recipients for one generation," said Gary Steinman, a twinning expert at Long Island Jewish Medical Center.
"It was not even known to anyone what the genetic code was at that time, let alone the ability to alter genes, which would have been necessary to carry over the twinning trait to future generations."
Steinman was not part of the Brazilian team's initial research, but he's now helping them search for genetic clues to the phenomenon.
If Not Mengele, Who?
One clue in the baptismal records may hold the real key to Cândido Godói's twins.
The greatest incidence of twinning, by far, is in the Linha São Pedro district, some 6 miles (10 kilometers) from the town center, the researchers found.
The neighborhood was settled in the early 20th century by just eight families. Today Linha São Pedro's 80 households are home to 44 pairs of twins.
The community's isolation and small size suggests an evolutionary origin for Linha São Pedro's outsize twin population. If a small group settles a region and the settlement remains isolated for generations, the original settlers' biological quirks tend to be passed down as the same families intermarry over and over—scientists call it the founder effect.
"By chance, one or two members of these families that started Linha São Pedro could have a genetic of predisposition to have twin births," Schuler-Faccini speculated.
Scientists aren't sure exactly which gene or genes are responsible for human twinning, but twin hot spots like Cândido Godói give researchers a chance to search for repeated clues in twin DNA.
Steinman, of Long Island Jewish Medical Center, suspects a role for a growth hormone-produced protein called IGF, which he's previously linked to twinning in both cows and humans. He hopes to discover whether Cândido Godói twins have high levels of IGF and, if so, whether there's a gene mutation responsible for high concentrations of the supposed twin-producing hormone.
Whatever the causes, the town's profusion of fraternal twins isn't even especially rare, said twinning expert Bruno Reversade, of the Institute of Medical Biology in Singapore, who is not involved in the Cândido Godói research.
"There are in Nigeria and Romania isolated villages like this one, but they have not gotten [or] sought publicity," said Reversade, who called the Mengele hypothesis "preposterous."
"I concur with the authors' conclusions that it may be a founder effect," he added.
Twins Spurred by Something in the Air?
Another theory suggests that environmental factors may be at least partly responsible for Cândido Godói's profusion of twins.
Locals have long suspected that something—perhaps a pesticide—in the town's water, food, or air may be boosting the twin birth rate, according to the Nazi Mystery documentary.
"We know that twinning can be related to environmental conditions," study leader Schuler-Faccini told National Geographic News. "For example, some studies suggest that women who [consume] more milk and dairy products are more predisposed to have twins."
One explanation doesn't preclude the other, she said. Cândido Godói's twins may be born of some combination of genetics and environmental factors.
But Camarasa, the historian, still believes Mengele may have played some role.
"There is still no convincing scientific explanation of the phenomenon," he said. "There are only hypotheses, and mine is one of them.
"I think that Mengele's life in exile still holds many secrets."
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