Equation 2 · Part 5 · Hominin Evolution and Deep Prehistory: A First-Principles Introduction

Symbol P_4

\hat{f} = \frac{\sum_{i} (P_2(i) - P_1(i))\,(P_4(i) - P_1(i))}{\sum_{i} (P_3(i) - P_1(i))\,(P_4(i) - P_1(i))}

P_4

What this part means

$P_4$ is one of the signed contributions combined to compute the quantity on the left.

Its job in the formula

$P_4$ is one of the signed contributions combined to compute the quantity on the left.

Full expressionSymbol P_4Article meaning

The passage around this formula

…and scale by how much variation the archaic and comparison genomes share with each other overall. A simplified version of the widely used D -statistic framework expresses this as: $\hat{f} = \frac{\sum_{i} (P_2(i) - P_1(i))\,(P_4(i) - P_1(i))}{\sum_{i} (P_3(i) - P_1(i))\,(P_4(i) - P_1(i))}$ . where $P_1$ through $P_4$ are allele frequencies at site i in an outgroup, a candidate-admixed population, a comparison population without the admixture, and the archaic source, respectively. The estimator exploits a simple logic: if population $P_2$ has interbred with the archaic lineage $P_4$ and $P_3$ has not, $P_2$ should…

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A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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