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O-22 - Pekar 2022 computed the two-introduction likelihood by squaring only the polytomy criterion, omitting the size-ratio and sequence-difference conditions imposed on one introduction

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Properties8
type
observation
id
O-22
statement
Pekar et al. 2022 evaluated the single-introduction likelihood as P(tau|I1)=0.031 by requiring simulations to meet four topology conditions (basal polytomy, lineage sizes between 30 and 70% i.e. |ln SR|<=ln(7/3), sequence difference D=2 with no intermediate genomes, and MRCA placement), but did not simulate the two-introduction model, instead setting P(tau|I2)=P(tau=tauP|I1)^2=0.475^2=0.226 from the polytomy criterion alone (times a ~0.6 MRCA factor), omitting the size-ratio and sequence-difference conditions.
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linked
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S-22 - Weissman 2026 — a fundamental Bayesian error in the multiple-introductions claim
locator
Sections 'The Central P2022 Argument' and 'Overview of the Remaining Corrections', p.51-53; quoting P2022 supplement p.13
quote
P(tau=tauP|In=I1) = 0.475 and P(tau=(tauP,tauP)|In=I2) = P(tau=tauP|In=I1)^2 = 0.226.
data_basis

Records the structure of P2022’s calculation (from P2022’s own simulations and supplement): I2’s likelihood used only the polytomy sub-criterion tauP applied twice, while I1’s likelihood additionally required the size-ratio and sequence-difference conditions. This asymmetry is the factual basis for Weissman’s error argument.

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