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Equation 1 · Part 5 · Darwin's Finches: The Beak the Grants Measured for Forty Years

superscript

R=h2SR = h^2 S
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What this part means

A raised number can be a power. When it is a label or bound, it selects a case or the upper limit of a sum; the formula’s structure distinguishes these uses.

Its job in the formula

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The passage around this formula

Heritability is what turns a measured selection differential into a testable prediction, through the simplest quantitative-genetics identity in the field, the breeder’s equation: R=h2SR = h^2 S. where S is the selection differential actually measured on the population in one generation, h2h^2 is the trait’s heritability, and R is the response: the amount the population’s mean should shift in the next generation, if the difference between survivors and non-survivors was genetic rather than purely environmental. Grant and Grant ran exactly this check on their own data, comparing the mean of a trait before a selection episode with the mean of the same trait in the following generation. The…

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An exponent tells how a base is used in multiplication. In x³, x is the base and 3 is the exponent: x³ = x × x × x.

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Sources cited in the surrounding passage

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