G25 authenticity check

Global25 coordinates carry a numeric signature from how they were produced. An original projection has a characteristic distribution and a consistent number of decimal places; a row that has been rounded, re-scaled, hand-edited or generated from a different calculator's output tends to depart from that in ways arithmetic can see. This tool inspects a pasted row for those departures — precision that has been lost, values that fall outside the range a real projection produces, digit patterns consistent with manual editing, and the fingerprints of a simulated rather than measured coordinate.

It matters because every downstream number inherits the input. Distances and admixture fits are arithmetic on these 25 values, so a row that was rounded to three decimals or assembled from a K36 conversion will produce clean-looking rankings that describe the conversion rather than the genome. Checking the row first is the cheapest way to avoid building an interpretation on top of a coordinate that cannot support it.

What it cannot do: this is a check on the numbers, not on provenance. It cannot prove a row is yours, cannot confirm which service produced it, and cannot certify a coordinate as genuine — a carefully constructed fake can pass, and an unusual but real coordinate can look suspicious. Read the result as evidence about how the row was probably handled, never as a verdict on the person it claims to describe. Everything runs in your browser; nothing you paste is uploaded or stored.

The commonest case is the forwarded row: coordinates received from a relative, a forum thread or an old email, provenance forgotten. Here the audit's precision checks earn their keep — an official projection carries full precision on every dimension, and a row that comes back flagged for truncated decimals has usually been through a spreadsheet whose display settings quietly rounded it. Distances computed from a rounded row drift by more than beginners expect, in whichever direction the rounding happened to fall.

The second case is the converted row: a coordinate manufactured from another calculator's output by one of the converter tools. These are simulations — numbers shaped like a projection that describe the conversion, not the genome — and they tend to fail the audit's distributional checks, sitting where no real projection lands. The tell that needs no tool at all: a real scaled row of a modern person lands within a few hundredths of some modern population; a row whose nearest population on Earth is past roughly 0.08 is unscaled, corrupted or simulated, whatever its story says.

The third case is your own row, checked before building on it — the cheapest habit in the hobby. Ten seconds here beats an evening interpreting distances a damaged paste produced. If the row passes, every downstream tool on this site reads it as-is; if it does not, the fix is almost always re-copying from the delivered file rather than anything genetic.

There is no equivalent audit in the standard toolkit. Vahaduo and nMonte consume whatever is pasted, faithfully; spreadsheets are where the damage happens, not where it is caught; and the coordinate service itself delivers rows but does not police what happens to them across two years of forwarding. The niche exists because the format is portable plain text — the property that made Global25 the community standard is the property that lets rows degrade silently in transit.

The check is deliberately conservative about its own verdicts. Numeric forensics can say a row's digits are consistent or inconsistent with an original projection; it cannot subpoena the row's history, and it says 'looks' rather than 'is' on purpose. For anything that matters — a paid analysis, an argument, a family question — the clean path is always the same: obtain the official row from the source service, keep both delivered forms labelled, and let this page confirm the copy you pasted is the copy you were sent.