The Genomic Scars of Antisemitism, 2022

Between election news and the ever-earlier encroachment of Christmas, an important November anniversary of a horrific event goes mostly unnoticed: Kristallnacht, the “night of broken glass.” Many think it signaled the start of the Holocaust.

Today is the 84th anniversary of Kristallnacht. I wrote the essay below on the 80th anniversary in 2018, following the massacre at the Tree of Life synagogue in Pittsburgh. But antisemitism persists, like a stubbornly metastatic cancer. Look at recent events.

On January 6, 2021, at the attack on the U.S. Capitol, insurrectionist Robert Keith Packer wore a hoodie emblazoned with “Camp Auschwitz.” Below it read “work brings freedom,” the statement that met prisoners arriving at the death camp.

Synagogues are still threatened. Certain celebrities are overtly antisemitic or post social media links to antisemitic films, seemingly too ignorant to recognize meaning or context. It is subtle, too, for “inclusivity” this time of year does not seem to apply to the diversity of religions, and especially to choosing not to identify with one.

The Anti-Defamation League defines antisemitism as “hatred toward Jews.” The organization changed “anti-Semitism” to one word with lower case “s” because the capital “S,” coined by a German historian in 1781, referred to a group of related languages originating in the Middle East, not ancestry or religion. But google and spellcheck have yet to catch up. I have to keep overruling the change as I write this.

It is unfortunate that I need to republish this article, updated slightly. The anniversary of Kristallnacht should bring chills to any group that is marginalized or the target of hate.

Original Publication Date: November 8, 2018

On November 9 and 10, 1938, Storm Troopers, Hitler Youth, and civilians rampaged through Nazi Germany. They shattered windows of more than a thousand synagogues, Jewish homes, and more than 7,000 businesses, and arrested some 30,000 Jews, cramming them into boxcars like doomed cattle and transporting them to concentration camps.

History books and the media chronicle the hatred and misplaced sense of superiority that fuels destruction of a people, like the remembrances of Kristallnacht. But evidence also lies in our genomes. That’s the case for the Ashkenazi Jews, whose ancestry traces back to Eastern Europe, not so very long ago. I am 100% Ashkenazi, my ancestors from what is now Ukraine.

A Series of Population Bottlenecks

Nazi Germany’s failed “final solution” left marks in our DNA, from genes to genomes. A striking example is the elevated frequency of mutations in the gene behind Canavan disease in the U.S., which traces back to two of the 250 or so souls who survived the massacre in the Vilna ghetto in Lithuania by running into the forest, in September 1943. I cover that story in my gene therapy book.

Genome-wide signals of past antisemitism come from farther back, especially from the near-extinction of the Jews during the Crusades. A population bottleneck echoes today in the genetic similarity among modern Ashkenazim.

A bottleneck is a term in population genetics that describes the near-decimation of a group, followed by restoration of numbers from a few individuals. The long-term effect is to narrow the gene pool, which amplifies persisting gene variants. Modern cheetahs in Africa illustrate a classic bottleneck, their near genetic uniformity reflecting population narrowing during the ice age that ended about 11,700 years ago. Poaching added to the diminishing genetic diversity.

The nature of the changeable DNA molecule enables researchers to estimate dates of past key genetic events. Differences in DNA sequence among modern human genomes provide a backward-ticking “molecular clock,” possible because genes mutate at known and measurable rates. The different mutation rates of different genes are based on the nuances of the DNA base sequence, which affects the likelihood of an error as DNA replicates, which can replace one DNA base with another. Mutation accumulation takes time – hence, the molecular clock of evolution.

The Ashkenazim have survived an undulation of population bottlenecks, a choreography of hatred that has serially strangled the diversity of our gene pool since our origins in the Levant (Egypt, Cyprus, Iraq, Palestine, Syria, Jordan, Lebanon, and Turkey) during Biblical times. The so-called Jewish Genetic Diseases are a legacy of repeated episodes of persecution. Any of these dozen or so conditions, from A (Alport syndrome) to Z (Zellweger syndrome), appears when an individual inherits two copies of the same recessive mutation from parents who shared a recent ancestor, like a great-grandparent.

After the Pittsburgh massacre, I searched for further info on the genomic scars of antisemitism, and quickly found a compelling report in PLOSGenetics. “The time and place of European admixture in Ashkenazi Jewish history,” from Shai Carmi of the Hebrew University and his colleagues, is from 2017. They used computational tools to expose how a severe population crash 30 or so generations ago, followed by an infusion of Eastern European DNA, brewed the Ashkenazi gene pool of today.

The Devastating Effect of the Crusades

From 1095 through 1291, Jews, regarded as killers of Jesus Christ, faced choices: convert to Christianity, be killed, or commit suicide. Entire communities of Jews vanished. On a spring day in 1171 in Blois, France, for example, the entire, albeit small, Jewish part of the community was burned at the stake.

By the thirteenth century the small-scale murders of Jews had metastasized into mass killings. The fourteenth century saw wholesale evictions of Jews from Western Europe, and by the fifteenth century, very few were left in Germany and France. Many survivors dragged themselves in pitiful migrations to Eastern Europe.

Historical records are scant. Genetic evidence, also incomplete, compares modern human genomes, or their parts, against a backdrop of geographic origins and known migration patterns. The result is a glimpse of what might have happened, the narrative that fits the genetic evidence.

In a paper from 2014 in Nature Communications, Dr. Carmi and his team report the sequencing of the genomes of 128 modern Ashkenazi individuals. The investigators found clues to the past in extensive DNA markers and sequences that are identical and linked on the same copy of a chromosome – a sign of shared ancestry. Such “identical-by-descent” chromosome regions reflect a population bottleneck so severe, those 30 or so generations ago, that the most likely explanation is that at one time during the late-medieval period, only 350 Ashkenazim existed!

Instead of analyzing entire genomes, the experiments described in the 2017 report focused on parts that vary. The researchers compared 252,358 single-DNA-base sites (SNPs) in the genomes of 2,540 Ashkenazim, 543 Europeans, and 293 Middle Easterners.

The computational analysis points to interbreeding (“admixture”) between populations from the Middle East and Southern Europe about 30 to 35 generations ago. But then a severe bottleneck came, at the time of the Crusades, followed by an infusion of genomes from Eastern Europe. The Ashkenazi gene pool formed from the Jews chased out of western European during the Middle Ages. We’re descended from the rejects of a supposedly civilized humanity.

And so the genomes of today’s Ashkenazim share six times as much of the DNA sequence with Eastern Europeans as they do with Southern Europeans, making our color-coded maps on Ancestry.com so alike that they extensively overlap or even become superimposable.

CODA 2022

I wish that this small slice of history did not reverberate as it does, its relevancy never fading, as some people hate those perceived as “other.” Let’s learn. Perhaps a wider recognition of Kristallnacht might be a step towards quelling the insidious genesis of antisemitism.