"Genetic testing breathes new life into Israel's Samaritans"

Samaritans celebrating Sukkot

All of these weird eugenic arguments people make about consanguinamory, about people having "too many kids," are not only creepy, but they're based on bad assumptions. When people are given easy access to good information on how to manage their families, they usually use it. The results can be amazing.

MT. GERIZIM, West Bank — When Ben Yehuda Altif got engaged to his first cousin Mazal, there was no problem winning the blessing of their families or the Samaritan high priest, who leads their ancient Israelite sect. Marriage between cousins is common in the religious community. But there was still an obstacle. Like many Samaritan couples today, the pair had to pass a premarital genetic screening to predict the likelihood of having healthy children. Without the green light from doctors, the marriage would be off. "Doctors said OK, and now we have a healthy, handsome boy," said Altif, 33, reaching for his wife's cellphone to show off pictures of their son.

Samaritans, who trace their roots back about 2,700 years, are best known for clinging to strict biblical traditions that have largely disappeared, including animal sacrifice, isolation of menstruating women and, until recently, a ban on marrying outsiders. But after facing near-extinction and being devastated by a high rate of birth defects because of inbreeding, the community is using modern science — including genetic testing, in vitro fertilization and abortion — to preserve their traditional way of life.

"It's changing our blood," said Aharon Ben-Av Chisda, 86, high priest of the 750-member Samaritan community, which is split about evenly between the West Bank village of Kiryat Luza near Nablus and the Israeli city of Holon, south of Tel Aviv. The white-bearded priest said genetic testing was breathing new life and optimism into the once-besieged community. He noted that he and his wife, who is a second cousin, had four children before genetic testing was available: Three are deaf and one can't walk. Most other families at Mt. Gerizim tell similar stories of health problems and handicaps among the older generation, though lately such problems have begun to disappear.

Samaritans are one of the world's oldest religious sects. Similar in practice, beliefs and ancestry to Jews, they follow the Hebrew Torah. But instead of Jerusalem, they revere a temple their ancestors built on this remote West Bank hillside.

Mentioned several times in the Bible, Samaritans are also considered one of the most inbred communities in the world, with 46% marrying first cousins and more than 80% marrying blood relatives, according to research by Israeli geneticist Batsheva Bonne-Tamir, who spent most of her career studying the community. The restrictions against marrying outsiders were less of a problem when Samaritans numbered more than a million in the 5th century. But because of persecution and forced conversion to Islam, their numbers had dwindled to just 146 by 1917. To crawl their way back, Samaritans began having large families of eight to 10 children, and the frequency of first-cousin marriages doubled, Bonne-Tamir found. As the population grew, so did the health problems and genetic defects, including rare blood diseases, Usher syndrome, deafness, muteness, blindness and physical handicaps.

"It was largely a 20th century phenomenon," said Bonne-Tamir, now retired from Tel Aviv University. Over the last decade, the community also relaxed its restrictions on intermarriage, allowing in about 25 women, mostly Jewish Israelis and arranged matches with brides from Ukraine. Samaritan leaders are reluctant to discuss their gene pool shrinkage, but they estimate the rate of birth defects was once 10 times higher than the nationwide average. By the 1960s, the rate of miscarriage was 10% higher among Samaritan women, one study found. But since adopting genetic testing, Samaritans say the rate of birth defects among newborns today is normal, even though most people still marry inside the community, including to relatives.

"This is enabling us to build a better generation for the future," said Ishak Al Samiri, a spokesman for the community at Mt. Gerizim.
Like his father, Al Samiri married a cousin. He has two healthy children, but he suffers from a blood disorder and his brother is crippled, both believed to be linked to genetic defects, he said.
Samaritans have long been the focus of genetic research, initially because of their ancient roots. In the 1960s, Israeli scientists began to study the Holon branch of the community, both to assist with genetic defects and to trace their historic lineage.

Samaritans claim that they are the descendants of northern Israelite tribes that were conquered by Assyrians. Subsequent genetic studies suggested that Samaritan men carry the so-called Cohen gene, linking them to ancient Israelites. For centuries, Samaritans lived in Nablus, but some moved to Jaffa and later to Holon. In 1988, the Nablus community relocated to a village near an Israeli settlement to escape attacks by Palestinians, who viewed them as Jews. Today Samaritans, who hold Israeli citizenship, pride themselves on staying neutral in the Israeli-Palestinian conflict.

 This can happen if there's a sudden, extreme bottleneck. Moderate levels of consanguineous marriage can have little to no consequence on a population's health stats, as long as the population is large enough and there is still non-consanguineous marriage. If a bottleneck does happen, it can be many generations before all of the deleterious genes from the founder population are eliminated from the gene pool. One of the ways to get around this, as the Samaritans have shown, is to use genetic tests to inform marital and reproductive decisions. If people are worried about children born with disabilities - and I'm assuming they're genuine here, and not just using this as an excuse to attack consanguinamorous people specifically - then a great way to address those concerns is with widespread, cheap access to genetic testing and family planning. As the Samaritans have shown, if you have that, consanguinamory isn't much of a problem.