I’m not a geneticist by trade. I’m an amateur who got stuck on a question that the big Beaker papers leave half-open, and then spent a long time trying to close it with public data only—the same call sets, tables and annotations everyone else can download.
The question sounds small. After the great ancestry turnover in Britain around 2450 BC, English Chalcolithic–Early Bronze Age genomes still carry roughly 7–9% ancestry that looks Middle/Late Neolithic-related. Where did that residue come from?
• Local British farmers absorbed into incoming communities?
• Or continental people who were already mixed before they arrived?
Those are different pasts. One implies survival and incorporation on this island. The other implies the “British-looking” fraction was already baked into migrant groups. Group averages hide the difference. You need to know whether almost everyone carries a thin layer, or whether a few people carry a lot and most carry none.
I thought public IBD, f-statistics, Y/mt labels, and the shape of published ancestry estimates would settle it. They don’t. What I think I have produced—and why I’m bothering to post—is a clearer map of why they don’t, and therefore where the problem has to be solved next. Not a funding pitch. A diagnosis.
What I actually found
1. The residue looks population-wide, not a mosaic of survivors.
On the Booth × Olalde overlap (n = 28), once one extreme individual (I2462) is set aside, the group is statistically homogeneous at about 7.15%. Between-person scatter is small; models where only a minority carry the component and everyone else carries none are excluded. Booth’s gradual rise through time reproduces—and it is a rise in everyone. That is a real result, and as far as I can tell it hasn’t been stated this way with a scripted dispersion bound behind it.
It still doesn’t tell you provenance. An already-mixed import is uniform from day one. A local pulse absorbed over ten to fifteen generations is uniform by the time we sample Early Bronze Age people. Same snapshot. Different histories.
2. The “trace it home” instruments fail on public products.
Long shared segments (IBD), allele-frequency contrasts aimed at British private drift, and uniparental “insular” screens all break under ordinary audits: leave-one-out, site pruning, shared-depth truncation, positive controls. The discriminating information—rare variants, fine Y structure, long-segment continuity at time depth—isn’t reliably in the 1240k / AADR-shaped data we all use. Sometimes the burial still holds it; the assay and the label conventions don’t.
3. Those are two different kinds of failure.
Three instruments fail because information was discarded (capture + harmonisation). The residue-shape instrument fails because information was erased (admixture before these people lived). Collapsing both into “we need more aDNA” is how you waste the next decade.
I also built a Sardinian re-imputation instrument to ask whether public IBD nulls are partly old pipelines rather than ascertainment. It validates within poles; the decisive cross-pole test is specified and not run due to the constraint of my available resources.
Where and how to solve it (not “who should fund it”)
If the goal is provenance of that 7–9%, the map is annoyingly specific:
A. Where the assay threw the information away
Hold the same individuals and change the data product: shotgun (or denser) sequencing → modern imputation → rare-variant / fine-lineage / IBD methods. Especially useful where the same person already exists in both capture call sets and shotgun releases (a clean ascertainment test). Published library-quality metrics for the people I’d prioritise suggest this is practical for most of that set, not all—some look too thin on public annotation alone.
B. Where time erased the information
Don’t keep sequencing well-sampled Early Bronze Age individuals expecting residue structure to reappear. Sample closer to the transition—Chalcolithic / earliest Bronze Age—where an absorbed local pulse might still show heterogeneity. That is a dating-and-excavation problem as much as a sequencing problem.
C. What not to confuse with a solution
More Beaker genomes won’t answer this. Ireland isn’t a free continuity control across the same interval. Collapsing Y strings to “I2” and calling it local doesn’t survive a shared-depth check. And a homogeneous ~7% background is evidence about structure, not a passport stamp for “British Neolithic survival.”
Why post this as an amateur?
Because the literature often states the residue, then slides past the provenance question—or treats every failed test as “low power” instead of “wrong information class.” I’m not claiming a final β. I’m claiming a usable negative architecture: four instruments, two kinds of limit, and a concrete split in where the next honest attempt has to go.
The draft paper:
Full deposit (pre-registrations, results, code, audit trail):
If I’ve got something wrong in the genetics, I want to hear it. If the diagnosis is roughly right, the next useful work isn’t another average—it’s either denser data on the right people, or older people on the right dates.
───
• “Uniform at 7% is a result. It just isn’t a provenance result.”
• “Some missing answers are missing chips. Some are missing centuries.”
• “I’m an amateur. The deposit is public. Please break it if you can.”
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