This post is based on the episode with Dr. Shamam Waldman who discussed a paper she co-authored with her colleagues at the Hebrew University of Jerusalem. The study was an effort to sequence the DNA from the remains of Ashkenazi Jews in medieval Europe.
Where did Ashkenazi Jews come from?
It is a question that has fascinated historians, geneticists, and Jewish communities for generations.
We know that Jewish communities existed in medieval Germany and France by the tenth century. We also know that their descendants eventually formed one of the world's largest Jewish populations, spreading across Central and Eastern Europe and later to communities around the globe.
But the earliest stages of Ashkenazi Jewish history remain difficult to reconstruct.
Did these communities descend from Jews who had lived in the region since Roman times? Did their ancestors migrate north from established Jewish communities in southern Italy? And how did a relatively small population develop the distinctive genetic characteristics observed among many Ashkenazi Jews today?
A remarkable ancient DNA study offers important clues.
In this episode of The Levantini Podcast, I speak with geneticist Shai Waldman about research published in the scientific journal Cell examining DNA recovered from individuals buried in a medieval Jewish cemetery in Erfurt, Germany.
The researchers analyzed genetic material from teeth associated with a Jewish community dating primarily to the fourteenth century.
Their findings revealed striking similarities between medieval Ashkenazi Jews and present-day Ashkenazi populations.
They also provided evidence that an important population bottleneck, or founder event, had already occurred by the Middle Ages.
But the study did not resolve every question.
The ultimate origins of Ashkenazi Jews, the precise routes of their migrations, and the relative contributions of different ancestral populations remain subjects of continuing research.
Who Are Ashkenazi Jews?
Ashkenazi Jews are Jewish communities whose historical roots lie primarily in medieval Western, Central, and Eastern Europe.
Their ancestors lived in regions including Germany, France, Poland, and other parts of Europe.
They developed distinctive religious traditions, communal institutions, and cultural practices over many centuries.
Other Jewish communities followed different historical trajectories.
Sephardic Jews are historically associated with the Iberian Peninsula, particularly Spain and Portugal, and their later diasporas.
Jewish communities also developed across the Middle East, North Africa, and elsewhere.
These categories describe broad historical and cultural traditions rather than completely separate biological populations.
They also do not imply that every individual within a community has identical ancestry.
Waldman's study focused specifically on the genetic history of Ashkenazi Jews.
The goal was to examine how much of the population's distinctive genetic profile could already be observed in medieval Europe.
When Did Ashkenazi Jewish Communities First Appear?
Historical records identify recognizable Jewish communities in parts of Germany and France by approximately the tenth century.
But the origins of those communities are uncertain.
Waldman explains that historians have considered several possibilities.
One theory proposes that Jews had lived in regions of Western Europe since the Roman period and gradually developed into the communities later identified as Ashkenazi.
Another suggests that some ancestors of Ashkenazi Jews migrated north from southern Europe, especially Italy.
Southern Italy had well-established Jewish communities during antiquity and the early medieval period.
Migrants from those communities could have contributed to the formation of Jewish settlements farther north.
But the historical records do not establish exactly when such migrations occurred, how many people participated, or what motivated them.
Waldman emphasizes that these remain open questions.
The genetic study from Erfurt provides evidence consistent with southern European ancestry, but it cannot identify a particular migration event.
Nor can it establish whether the ancestors of the Erfurt community had lived in Germany continuously since Roman times.
The distinction matters.
Genetic evidence can help reconstruct population relationships.
It cannot automatically supply the missing historical narrative.
What Is the Ashkenazi Jewish Founder Effect?
One of the most important concepts in the interview is the founder effect.
A founder effect occurs when a population descends from a relatively small ancestral group.
Because that group carries only a subset of the genetic variation present in a larger population, certain variants can become unusually common among its descendants.
Imagine a community formed by a limited number of families.
Each person carries genetic variants, many of which are harmless.
Some individuals may also carry variants associated with inherited diseases.
If the population remains relatively small and marriage occurs largely within the community, those variants can persist and sometimes increase in frequency.
Over many generations, the descendants of that community may share genetic characteristics that are uncommon elsewhere.
This is one of the major features of Ashkenazi Jewish population genetics.
Researchers have long identified evidence of a pronounced historical bottleneck.
Waldman explains that previous studies estimated effective population sizes in the hundreds.
An effective population size, however, is a technical genetic measure.
It is not necessarily the actual number of people living in a community.
For example, an estimated effective population size of 300 does not mean that exactly 300 people were alive at the time.
The real population could have been larger.
Waldman discusses how different genetic analyses have produced different estimates and suggests that historical Ashkenazi groups may have experienced bottlenecks of differing severity.
This raises the possibility that medieval Ashkenazi communities were more genetically diverse than their present-day descendants.
Why Are Certain Genetic Diseases More Common Among Ashkenazi Jews?
The founder effect also helps explain why some inherited disease-associated variants occur at elevated frequencies among people with Ashkenazi ancestry.
Every human population carries genetic variants.
Some variants are harmless, while others can increase susceptibility to disease or cause inherited disorders.
When a small ancestral population carries a particular variant, many descendants may inherit it.
For recessive disorders, a child generally needs to inherit disease-causing variants in the same gene from both parents to develop the condition.
If both parents carry the same recessive disease-associated variant, the chance of having an affected child increases.
This is one reason genetic carrier screening can be important in family planning.
However, not every disease-associated variant operates through recessive inheritance.
Variants linked to hereditary cancer susceptibility, for example, may involve different inheritance patterns.
Waldman discusses the identification of variants associated with conditions including breast cancer susceptibility and Parkinson's disease among the medieval Erfurt samples.
The significance is historical.
Some variants found among Ashkenazi Jews today were already present in the population centuries ago.
They were not all recent developments.
The study therefore provides direct evidence that features of the modern Ashkenazi genetic profile had already emerged by the fourteenth century.
Endogamy and Jewish Population History
Another important concept is endogamy.
Endogamy refers to marriage primarily within a particular community or population.
Waldman explains that Ashkenazi Jewish populations exhibited substantial endogamy during the medieval period.
This contributed to the persistence of genetic variants associated with the founder effect.
But she also makes an important distinction.
Genetic endogamy does not mean that Jewish communities never interacted or intermarried with neighboring populations.
Nor does it imply that all Ashkenazi Jews descend exclusively from a single ancestral source.
The genetic evidence itself indicates that historical admixture occurred.
The more precise point is that the ancestors of present-day Ashkenazi Jews formed a relatively continuous population in which marriage within the community was common.
This helps explain why genetic patterns established in the Middle Ages remain recognizable today.
It also helps explain why researchers can compare medieval DNA with modern Ashkenazi genetic data.
Why Study a Jewish Cemetery in Erfurt?
Erfurt, in present-day Germany, had an important medieval Jewish community.
Waldman explains that Jewish settlement there dates to the late eleventh century.
The community developed over the following centuries, becoming part of the wider network of Jewish life in medieval Central Europe.
But its history was marked by violence.
In the middle of the fourteenth century, a devastating anti-Jewish attack killed many members of the community.
The attack occurred during a period of widespread persecution of Jews in Europe.
Waldman notes that the timing of the Erfurt violence is important because the Black Death had not yet arrived in the city.
The attack therefore should not simply be explained as a local response to the plague's arrival.
After the massacre, the city eventually allowed Jews to return.
A new Jewish community developed, including immigrants from areas farther east.
Historical rental records provide evidence of these later movements.
The renewed community became substantial, but Jewish life in Erfurt was again disrupted when Jews were expelled during the fifteenth century.
This complicated history made the medieval cemetery especially valuable for genetic research.
It also raised an important question.
Did the individuals whose DNA was analyzed belong to the community before the massacre, the community established afterward, or both?
Were the DNA Samples from Before or After the Erfurt Massacre?
The answer is not entirely certain.
Waldman explains that researchers attempted to date the remains using radiocarbon analysis.
Unfortunately, the resulting date ranges were too broad to distinguish conclusively between individuals who lived before and after the mid-fourteenth-century massacre.
Archaeological evidence suggests that the particular section of the cemetery examined in the study was more likely used by the later Jewish community.
Some genetic findings also showed affinities consistent with populations from farther east in Europe.
That observation is compatible with historical evidence that the reestablished community included migrants from eastern regions.
But it does not prove the date or origin of any individual.
One skeleton showed evidence of a violent death.
However, researchers did not identify a broader pattern of injuries suggesting that the excavated group represented victims of the massacre.
Waldman therefore cautions against assigning specific individuals to the earlier community on the basis of the available evidence.
The study provides an extraordinary genetic snapshot of medieval Jewish Erfurt.
It does not provide a complete genetic reconstruction of the city's Jewish population before and after the massacre.
How Were Researchers Able to Study Medieval Jewish Remains?
One of the most unusual aspects of the project was the opportunity to study ancient Jewish DNA at all.
Jewish burial traditions generally place great importance on the respectful treatment of human remains.
Disturbing graves for research can raise serious religious and ethical concerns.
Waldman explains that the Erfurt study became possible because of a particular set of circumstances.
After the medieval Jewish community disappeared, a granary was constructed over part of the former cemetery.
Centuries later, a redevelopment project required excavation in a limited section of the site.
The remains were going to be moved and reburied.
This created a rare opportunity to examine material from an archaeologically documented Jewish cemetery without initiating an excavation solely for genetic research.
The researchers worked with rabbinical authorities and the local Jewish community.
Permission was granted to analyze detached teeth from the excavated remains.
Teeth can preserve ancient DNA, making them valuable for genetic analysis.
The project therefore illustrates the importance of collaboration between scientists, archaeologists, religious authorities, and descendant communities.
It also highlights a major limitation in the study of Jewish population history.
Comparable ancient DNA samples from other Jewish communities are difficult to obtain.
Burial Customs and the Direction of Jerusalem
The Erfurt cemetery also revealed evidence of medieval Jewish burial practices.
Waldman describes how nearly all the individuals were buried with their feet oriented toward Jerusalem.
This arrangement was consistent with religious traditions concerning resurrection and the anticipated return to Jerusalem.
One woman was buried in the opposite direction.
Her children, who were also represented among the samples, followed the more common orientation.
Waldman attempted to investigate whether the woman's unusual burial position might be explained by some distinctive circumstance.
But the available evidence provided no answer.
There is no basis for concluding that she was punished, excluded, or treated differently because of misconduct.
The detail is a reminder that archaeological discoveries sometimes reveal differences we cannot explain.
Not every unusual feature has a recoverable historical meaning.
What Did the Erfurt DNA Reveal?
The central finding was that the medieval individuals already carried genetic characteristics strongly associated with present-day Ashkenazi Jews.
Waldman discusses both disease-associated variants and neutral variants.
Neutral variants are genetic differences that do not themselves cause disease.
Researchers compared the medieval genomes with genetic patterns identified in modern Ashkenazi populations.
They found variants that are relatively common among Ashkenazi Jews today but rare in many comparison populations.
The presence of these variants in medieval Erfurt supports the conclusion that important features of the modern Ashkenazi genetic profile were already established.
It also provides evidence that the founder event occurred before the individuals in the cemetery lived.
This is significant because previous genetic studies had reconstructed the bottleneck largely from the DNA of living people.
Ancient DNA allows researchers to test those historical inferences against actual medieval genomes.
Instead of estimating the past exclusively from present-day populations, scientists can examine evidence from people who lived centuries earlier.
That is what makes the Erfurt study especially important.
Did Medieval Ashkenazi Jews Already Carry Modern Disease-Associated Variants?
Yes, some did.
Waldman explains that researchers identified several genetic variants associated with conditions known in present-day Ashkenazi populations.
These included variants linked to hereditary breast cancer susceptibility and Parkinson's disease.
But identifying a variant does not mean that the individual necessarily developed the associated condition.
Some variants increase risk rather than guarantee disease.
Others require particular combinations of inherited variants to cause a disorder.
The study cannot reconstruct each individual's complete medical history.
Its importance lies in showing that particular genetic variants were present in the medieval population.
This strengthens the evidence that the Ashkenazi founder effect preceded the fourteenth century.
It also demonstrates that aspects of present-day genetic disease risk have a long population history.
What Can Mitochondrial DNA Tell Us About Ashkenazi Ancestry?
One of the most fascinating parts of the conversation concerns mitochondrial DNA.
Mitochondrial DNA is inherited primarily through the maternal line.
Because it follows a different inheritance pattern from most nuclear DNA, it can help researchers investigate maternal ancestry.
Earlier genetic research had identified mitochondrial lineages shared by substantial proportions of Ashkenazi Jews.
Waldman's team found that one common maternal lineage was also present among the Erfurt individuals.
In the interview, she explains that 11 of the 33 individuals discussed carried the same mitochondrial DNA type.
This does not mean that they all had the same recent mother.
Rather, it indicates that they shared a maternal ancestor at some point in the past.
Waldman emphasizes that estimating when that ancestor lived involves considerable uncertainty.
The analysis was consistent with a common maternal ancestor in the first millennium CE, but the possible date range was broad.
The finding provides another line of evidence for the effects of a relatively small ancestral population.
It also illustrates how different forms of genetic data can reveal different aspects of population history.
Did Ashkenazi Jews Originate in Southern Italy?
The question of southern European ancestry is particularly important.
One longstanding theory proposes that ancestors of Ashkenazi Jews migrated from established Jewish communities in southern Europe into regions farther north.
Southern Italy is a prominent candidate because of its Jewish population during antiquity and the early medieval period.
Waldman explains that the Erfurt genomes contain ancestry components consistent with southern European and Middle Eastern population relationships.
However, distinguishing those components precisely is difficult.
The researchers used present-day populations as genetic reference groups.
Modern Italians and modern Middle Eastern populations are not identical to the populations that lived one or two thousand years ago.
Furthermore, southern Europe and the Middle East have experienced substantial historical population mixing.
As a result, genetic models can assign different proportions of ancestry depending on the populations used for comparison.
Waldman cautions against interpreting those estimates as exact historical percentages.
The findings support the possibility of southern European ancestry among medieval Ashkenazi Jews.
But they do not prove that a particular group migrated from Italy at a particular date.
Nor can the study determine whether all relevant ancestors were members of older Jewish communities or whether some were converts to Judaism.
These remain open historical questions.
What About Middle Eastern Ancestry?
The relationship between Ashkenazi Jewish ancestry and the ancient Middle East is another central issue.
Jewish historical and religious traditions connect the origins of the Jewish people to the land of Israel and the wider ancient Near East.
But identifying precise lines of genetic continuity requires suitable comparison data.
Waldman explains that separating Middle Eastern and southern European ancestry in the Erfurt genomes is challenging.
The study identifies genetic relationships consistent with ancestry from these broader regions, but it cannot establish exact proportions or reconstruct the full sequence of historical population movements.
It is therefore important not to treat an ancestry estimate based on modern reference populations as a direct measurement of an ancient community's ethnic or religious identity.
A genetic profile cannot independently tell us whether an ancestor practiced Judaism, converted to Judaism, or belonged to a particular historical community.
Those questions require additional evidence.
The strongest conclusion is that the medieval Erfurt population shared substantial genetic continuity with present-day Ashkenazi Jews and carried ancestry reflecting a complex population history.
Why More Ancient Jewish DNA Matters
Near the end of our conversation, I asked Waldman what researchers might learn if they could analyze DNA from older Jewish communities in the Middle East.
Her answer was revealing.
Direct comparisons between ancient Jewish remains from the Middle East and medieval or present-day Jewish populations could help test hypotheses about population continuity.
Such evidence might help researchers determine whether particular ancient communities contributed ancestry to later Jewish populations.
Comparable samples from medieval Spain could also shed light on relationships between Sephardic and Ashkenazi Jews.
And samples from other medieval Ashkenazi communities could reveal whether Erfurt was representative or genetically distinctive.
But there are major obstacles.
Ancient DNA research depends on the preservation of usable genetic material.
It also depends on archaeological context, reliable dating, ethical permissions, and appropriate comparison data.
For Jewish burials, religious concerns surrounding the disturbance of graves are particularly significant.
Waldman suggests that some ancient DNA samples already held in research collections might eventually prove relevant if their Jewish community associations could be established through independent evidence.
That possibility is intriguing.
But until suitable samples become available, important questions will remain unanswered.
What the Erfurt Study Changes About Jewish History
The Erfurt research does not provide a complete answer to the origins of Ashkenazi Jews.
It does something different, and arguably more important.
It places direct genetic evidence into a historical period that had previously been reconstructed largely from later populations.
The researchers found that medieval Ashkenazi Jews already shared genetic characteristics with their present-day descendants.
They identified variants associated with the population's founder effect.
They documented maternal lineages that remain common today.
And they uncovered evidence suggesting that medieval Ashkenazi populations may have been more internally diverse than the modern population.
The study also illustrates the importance of combining genetics with history.
Without the archaeological context of the Erfurt cemetery, the DNA would tell a much less meaningful story.
Without historical records of the city's Jewish community, researchers would have fewer ways to interpret its population changes.
And without careful attention to the limitations of ancestry modeling, the genetic results could easily be overstated.
Conclusion: Ancient DNA and the Origins of Ashkenazi Jews
The origins of Ashkenazi Jews remain one of the most fascinating questions in Jewish population history.
The medieval Erfurt study brings us closer to understanding that history, but it does not resolve every debate.
Its strongest finding is the remarkable genetic continuity between medieval Ashkenazi Jews and the population today.
By the fourteenth century, many of the genetic characteristics associated with modern Ashkenazi Jews were already present.
The population's founder effect had occurred.
Distinctive maternal lineages were established.
And variants associated with inherited disease risk were already circulating.
But the earlier story remains uncertain.
Exactly where the founding communities formed, how they migrated, and how different ancestral populations contributed to their development are questions that future research may help answer.
My conversation with Shai Waldman offers a fascinating look at what ancient DNA can reveal about Jewish history—and an equally important reminder of what it cannot yet tell us.
Ashkenazi Jewish Origins and Medieval DNA: Frequently Asked Questions
1. Where did Ashkenazi Jews originate?
Ashkenazi Jewish communities developed in medieval Western and Central Europe, with recognizable communities appearing in Germany and France by approximately the tenth century. Their earlier population history is still being investigated.
2. What is the Erfurt medieval Jewish DNA study?
It is an ancient DNA study published in Cell that examined genetic material from individuals buried in a medieval Jewish cemetery in Erfurt, Germany. The researchers compared the medieval genomes with present-day populations to investigate Ashkenazi Jewish population history.
3. What did the Erfurt DNA study discover?
The study found that medieval Ashkenazi Jews already carried genetic characteristics associated with present-day Ashkenazi populations. It also provided evidence that an important population bottleneck had occurred before the fourteenth century.
4. What is the Ashkenazi Jewish founder effect?
The founder effect refers to a population descending from a relatively small ancestral group. Genetic variants carried by that group can become unusually common among later descendants.
5. How many people founded the Ashkenazi Jewish population?
Genetic studies have produced estimates of effective population sizes in the hundreds, but effective population size is not the same as an actual historical headcount. The exact number of individuals in the ancestral communities is unknown.
6. Why are some inherited diseases more common among Ashkenazi Jews?
A historical founder effect and long periods of substantial marriage within the community contributed to elevated frequencies of certain inherited genetic variants.
7. What is endogamy?
Endogamy is the practice or pattern of marrying primarily within a particular population or community. It can contribute to the persistence of shared genetic variants over generations.
8. Did medieval Ashkenazi Jews already carry disease-associated genetic variants?
Yes. The Erfurt researchers identified some variants associated with diseases or disease susceptibility that are also found among present-day Ashkenazi populations.
9. Did the Erfurt study find shared maternal ancestry?
Yes. In the interview, Waldman explains that 11 of the 33 individuals discussed carried the same mitochondrial DNA lineage, indicating shared maternal ancestry farther back in time.
10. Did Ashkenazi Jews originate in southern Italy?
Southern Italy is one proposed source of migration into medieval Western Europe. The Erfurt genetic findings are consistent with southern European ancestry but do not prove a particular migration route or establish the complete ancestry of the founding population.
11. Do Ashkenazi Jews have Middle Eastern ancestry?
Genetic analyses identify relationships involving Middle Eastern and southern European ancestry, but estimating precise contributions is difficult because the populations of these regions have experienced extensive historical mixing.
12. Why was Erfurt important in medieval Jewish history?
Erfurt had an established Jewish community by the late eleventh century. Its history included a devastating fourteenth-century massacre, subsequent Jewish resettlement, and eventual expulsion in the fifteenth century.
13. Were the Erfurt DNA samples from victims of the medieval massacre?
Researchers could not conclusively identify the samples as belonging to massacre victims. Archaeological evidence suggested that the sampled cemetery section was more likely associated with the later Jewish community.
14. Why were researchers allowed to analyze teeth from the cemetery?
The remains had already been excavated during necessary redevelopment work. The research proceeded with rabbinical permission to analyze detached teeth and approval from the local Jewish community.
15. Were the individuals buried facing Jerusalem?
Almost all the individuals discussed were buried with their feet oriented toward Jerusalem. One woman was buried in the opposite direction, and the researchers could not determine why.
16. What does the study tell us about Jewish genetic continuity?
It provides direct evidence that important genetic features of present-day Ashkenazi Jews were already present in a medieval Jewish population in Germany.
