Natufian and C6: seven failures behind r/JewishDNA’s ancestry fan fiction
Natufian and C6 fan fiction on r/JewishDNA turns a prehistoric calculator coefficient into a Jewish ancestry meter and an averaged Roman coordinate into an entire historical population. Then conditional arithmetic is presented as a decisive verdict on ancestry. The confidence is enormous. The evidentiary foundation is considerably smaller.
A comment by u/Any_Green_17 illustrates the problem. The poster attacks a model assigning an Italian Jewish target 52.2% Roman and 34.6% Levantine ancestry, invokes Natufian estimates of 16.6% for the target and 6.2% for Roman C6, and calculates a supposedly required Levantine-source value of 38.62%.
From there, the comment declares overfitting and suggests that the model’s author may have selected a source deliberately to minimize Levantine ancestry. But calculating a conditional requirement is not the same as demonstrating a contradiction, diagnosing overfitting, or establishing manipulation. The comment slides between those claims as though they were interchangeable.
1. Any_Green_17’s Natufian and C6 calculation: what it actually says
The argument deserves to be laid out explicitly. In the comment, Any_Green_17 writes:
“According to you, the Italian Jewish sample is 52.2% Roman and 34.6% Levantine. I don’t know exactly what Levantine source you’re using, but the Italian Jewish sample has approximately 16.6% Natufian, and Roman C6 is 6.2% Natufian.”
u/Any_Green_17, r/JewishDNA
The calculation then proceeds through three steps:
0.522 × 6.2% = 3.2364 percentage points
16.6% − 3.2364% = 13.3636 percentage points
13.3636 ÷ 0.346 = 38.6231%, approximately 38.62%
The numerical operations are correct. Whether they describe the actual model depends on the assumptions examined below.
The poster then declares:
“Your model is clearly overfitting.”
“Another explanation could be that you actually used a source that was 38% Natufian so that European Jews could score as little Levantine as possible.”
u/Any_Green_17, r/JewishDNA
Here is the central failure: 38.62% is not itself a contradiction. It is the source coefficient required under the stated assumptions. To establish a contradiction, the poster would need to identify the actual Levantine source, estimate its Natufian coefficient under a compatible specification, and demonstrate a meaningful discrepancy after accounting for uncertainty and model residuals.
Instead, the comment acknowledges not knowing exactly which source was used and nevertheless pronounces the model defective. An unidentified source has effectively been convicted before it has been examined. If the actual source did yield approximately 38.62% under compatible conditions, that would satisfy this particular equation. It would not prove that the source had been chosen dishonestly.
2. The missing 13.2% and the assumptions behind the verdict
The Natufian and C6 arithmetic also leaves part of the ancestry model outside its accounting. The two quoted assignments total 52.2% + 34.6% = 86.8%. That leaves 13.2%. Assigning every remaining Natufian percentage point to the Levantine source implicitly gives those other sources zero contribution.
The complete conditional equation
16.6 = 0.522 × 6.2 + 0.346 × L + 0.132 × O
L = the Levantine source’s Natufian percentage.
O = the weighted Natufian percentage of the remaining sources.
L = (13.3636 − 0.132 × O) ÷ 0.346
| Assumed Natufian in the remaining sources | Required Natufian in the Levantine source |
|---|---|
| 0% | 38.62% |
| 5% | 36.72% |
| 10% | 34.81% |
If the omitted sources genuinely contribute zero under the same specification, the 38.62% calculation survives this accounting check. That possibility does not rescue the subsequent historical verdict. It simply means this particular assumption would have been justified. Show the complete model and establish it.
Three further premises remain unresolved: whether 16.6% describes the exact Italian Jewish target; whether the target and sources were evaluated using compatible prehistoric references and settings; and whether the fitted coefficients can be transferred between the models with sufficient accuracy.
Nor would a mismatch establish “overfitting.” Overfitting concerns a model capturing features that do not generalize; an unexpected cross-model coefficient does not diagnose it. Source mismatch, omitted contributions, an inappropriate benchmark and model incompatibility require different tests. The accusation of deliberate manipulation requires still more evidence. The comment jumps from an equation to a diagnosis to a motive without supplying the missing steps.
3. Natufian and C6: an average is not an ancient Roman person
The ItalyImperialRomanC6 coordinate under discussion is a cluster average. It is not an individual genome with one burial, one date and one life history. In Antonio et al. (2019), C6 belongs to a clustering framework describing Roman genetic diversity. A later G25 average derived from a cluster additionally requires documentation of its membership and construction.
A centroid summarizes where a collection sits while concealing its spread. It cannot tell readers that every included individual had the same ancestry profile. Nor must a constrained Natufian fit to the centroid equal the average of separate constrained fits to all its members.
That matters to Any_Green_17’s proposed explanation that low-Natufian West Asian ancestry within C6 is absorbing ancestry that should be assigned to an Israelite source. This is a testable hypothesis about proxy behavior. The equation does not establish it. Demonstrating it requires the actual sources, alternative fits and residual comparisons.
A problem with one C6-based model would establish a problem with that model. It would not dispose of Imperial Italy’s diverse populations. C6’s historical prevalence would not automatically validate it as a source, and criticizing that source would not invalidate every Italian contribution.
My individual ancient Italian comparisons address identifiable genomes. Their dates, locations and affinities remain evidence that requires explanation. The samples below are not asserted to be the documented membership of the exact C6 coordinate used on Reddit; that membership must be established separately.
4. Individual Imperial genomes break the Natufian ranking shortcut
The Natufian and C6 narrative becomes especially weak when an average replaces inspection of actual people. These five ancient Italian individuals from my research compilation show why. All distances below use the same German Ashkenazi reference.
| Individual | Modeled Natufian | German Ashkenazi distance |
|---|---|---|
| R835 | 4.0% | 0.0259 |
| R47 | 7.5% | 0.0241 |
| R1544 | 11.6% | 0.0266 |
| R134 | 12.1% | 0.0300 |
| R1549 | 17.3% | 0.0448 |
Orange: Natufian, scale 0–20%. Blue: German Ashkenazi distance, scale 0–0.0500. Compare each color on its own scale.
R47 is the closest German Ashkenazi match in this selected comparison. R1549 has the highest Natufian estimate and the largest distance. This tests a simplistic ranking rule, not a population-wide correlation.
R47 at 7.5% and R835 at 4.0% are substantially closer to German Ashkenazim than R1549 at 17.3%. R835 also places Ashkenazi Belarus at 0.0235 and Campania at 0.0238: almost equal affinities despite its low Natufian estimate.
Other individuals lean more clearly Southern Italian. R1554, with 10.9% Natufian, places Salentine Apulia at 0.0303 and Ashkenazi Poland at 0.0367. R1544, with 11.6%, is closer to Calabria at 0.0230 than to German Ashkenazim at 0.0266.
These comparisons demonstrate that the coefficient cannot replace the wider genome. More Natufian does not automatically produce a closer Ashkenazi match, and an averaged Roman label cannot explain away individual Roman evidence.
5. My 2.4% result exposes the dilution excuse
My genealogy is approximately 75% Eastern European Ashkenazi, 12.5% Southern Italian and 12.5% English. Yet IllustrativeDNA assigns me only 2.4% Natufian. The rest of its Hunter-Gatherer & Farmer output is 59.2% Anatolian Neolithic Farmer, 18.6% European Hunter-Gatherer, 13.0% Caucasus Hunter-Gatherer and 5.8% Zagros Neolithic Farmer. See my IllustrativeDNA proxy-bias analysis.
Invoking my non-Ashkenazi quarter does not automatically explain this. Under a simplistic additive model, an assumed Ashkenazi ancestral average of 10%, 15% or 20% would contribute 7.5%, 11.25% or 15% to a three-quarter-Ashkenazi descendant—even assigning zero to the remaining quarter.
Shared scale 0–15%. Blue: hypothetical additive contributions. Orange: reported output.
These assumed averages are conditional illustrations, not measurements of my ancestors or the Ashkenazi population. Calculator coefficients are not guaranteed to follow this inheritance arithmetic.
The point is consistency. Anyone treating Natufian as an additive historical quantity must confront what that assumption predicts. Anyone acknowledging that the output is model-dependent must stop presenting a preferred coefficient as an obligatory ancestry threshold. My result challenges that threshold rhetoric; it does not establish a population average.
6. Natufian and C6 benchmarks depend on models and tiny panels
G25 mixture coefficients depend on the chosen references. Coordinate averaging is linear, but constrained fitting is not automatically linear across targets and specifications. Correlated sources can trade contributions, weights can hit zero, and approximate fits retain residuals. Even a linear fitting procedure needs compatible inputs before its outputs can support cross-model accounting.
The Natufian and C6 calculation supplies no demonstrated calibration for that transfer. Nor can a prehistoric reference component be converted automatically into a percentage of historical Judean ancestry. Those are different historical questions.
Reported calculator changes illustrate the problem. In “Ashkenazi Jew: Thoughts?”, a self-described Ashkenazi commenter reports Natufian falling from 17% to 11% while Canaanite rises from 41% to 49%. In a Polish/Lithuanian Jewish results discussion, another commenter reports approximately 7%, compared with 11% and 14% for full siblings. These are reported results, not controlled population estimates.
A G25 calculator author on Eupedia also warns that their particular model can inflate Natufian and depress Zagros. That admission concerns that calculator, but it demonstrates why component allocation needs scrutiny rather than blind acceptance.
My earlier Italki Natufian critique examined ten Italian Jewish individuals averaging 14.5%, compared with fourteen Sicilian and Calabrian individuals averaging 7.0%. The current research notes identify a nine-person Italki reference. These panels must remain distinct, and neither establishes the provenance of Any_Green_17’s 16.6%.
Publish the individuals, weighting, relatedness checks and model settings. A tiny panel’s average cannot become a universal population benchmark through repetition. My experience of r/JewishDNA is that dissent gets censored while favored narratives receive protection. Whatever a discussion forum rewards, its visible results are not a representative population survey.
7. Natufian and C6 claims do not refute the evidence beyond G25
The Italian-related signal exists beyond the Reddit model. Separate analyses using medieval genomes, qpAdm and local ancestry inference require substantive answers.
| Analysis | Reported result | Method and target |
|---|---|---|
| Brace et al. (2022) | Approximately 67% Sicilian and 33% Turkish Jewish | qpAdm modeling of medieval Norwich individuals with modern proxies |
| Waldman et al. (2022) | Mean 65% South Italian, 19% Middle Eastern and 16% Eastern European | Plausible South-Italian-source qpAdm models for medieval Erfurt Jews |
| Lerga-Jaso et al. (2025) | 68% Italian and 16.6% Levantine, plus other assignments | Orchestra analysis of modern Ashkenazi genomes with Ashkenazi excluded as a source category |
| Steven Parker, Table 7 | 69.97% Italian South, 22.06% Lebanese and 7.97% Russian | Author-generated qpAdm model for Jew_Ashkenazi.HO; p = 0.1445 |
My How Ashkenazi Origins Were Mis-modeled tests source sensitivity directly. Replacing Southern Italian with Northern Italian changes the Lebanese coefficient from 22.06% to 42.57%; the Central Italian version yields 33.83%. Model p values are 0.1445, 0.0256 and 0.0514 for South, North and Central respectively. These are results under the specified configuration, not probabilities that a historical narrative is true.
Table 8 supplies a separate comparison: reported Ashkenazi FST distances of 0.0049 to Southern Italians, 0.0049 to Cretans, 0.0052 to Sicilians and 0.0055 to Greeks. These measure population differentiation, not ancestry fractions. They document Mediterranean proximity that the Reddit comment’s single-component arithmetic does not explain.
The modern proxies themselves contain complex ancestry. A Sicilian coefficient does not represent ancestry stripped of earlier eastern Mediterranean inputs. That is precisely why historically relevant references and careful interpretation matter.
Conclusion: the Natufian and C6 verdict was never demonstrated
Any_Green_17 begins by admitting uncertainty about the Levantine source and ends by declaring overfitting and suggesting deliberate source manipulation. The calculation between those statements does not bridge the gap. It produces a conditional requirement of 38.62%, not a demonstrated contradiction with the actual source. The remaining 13.2%, the provenance of the 16.6% benchmark, and compatibility between the models all require examination before that requirement can become a meaningful diagnostic.
The C6 argument fails at a different level. An average represents a collection of genomes; it does not make them interchangeable or exhaust the ancestry profiles present in Imperial Italy. My individual comparisons show precisely why that distinction matters. R835 and R47 retain close Ashkenazi affinities with substantially lower modeled Natufian than R1549. An argument about a centroid leaves those individuals—and the diversity they document—unanswered.
My own 2.4% IllustrativeDNA result and the reported calculator changes add another problem for the proposed yardstick: these coefficients cannot simply be treated as fixed hereditary credentials. Meanwhile, Brace, Waldman, Orchestra and my own analyses supply Italian-related findings that must be assessed through their actual methods. A Reddit equation does not supersede them by assertion.
The defensible conclusion is that Any_Green_17 has not established the historical verdict attached to the arithmetic. That does not automatically validate every competing model. It places the burden exactly where it belongs: on anyone claiming to have disproved one. Identify the actual source, show compatible estimates, test the complete mixture and address the individual genomes.
This is what makes the Natufian and C6 narrative ancestry fan fiction: conditional outputs are promoted into historical certainty, while the evidence needed to justify that promotion is missing. Decimal places do not turn an assumption into a finding. A cluster average does not erase individual Romans. And an accusation does not become a result because it is delivered confidently on r/JewishDNA.