Equation 3 · Part 2 · Darwin's Finches: The Beak the Grants Measured for Forty Years
superscript
superscript
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
A raised mark can be a power or an index. Its position and the surrounding notation determine which.
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The passage around this formula
where S is the selection differential actually measured on the population in one generation, 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 two independent beak traits, size and shape, evolved in the direction and close to the magnitude the equation predicted, with predicted and observed responses correlated at r = 0.832 across ten such…
Learn the underlying idea
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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