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Equation 1 · Part 6 · Dunbar's Number: The Limit That Might Not Exist

=

log⁡(Ngroup)=α+β⋅log⁡(VneocortexVrest of brain)\log(N_{\text{group}}) = \alpha + \beta \cdot \log\left(\frac{V_{\text{neocortex}}}{V_{\text{rest of brain}}}\right)
=

What this part means

The expressions on both sides represent the same quantity under the stated assumptions.

Its job in the formula

The equals sign connects the complete expression on the left with the complete expression on the right. Both sides must have compatible units.

The passage around this formula

The prediction itself has a precise origin and it is much narrower than its reputation. Robin Dunbar’s 1992 paper in the Journal of Human Evolution ran a comparative regression across primate genera and found that group size tracked one variable with real predictive power — the ratio of neocortex volume to the volume of the rest of the brain — while the ecological variables he tested alongside it, tied to diet and ranging behavior, did not [ 1 ] . Stated as a model, the claim was this: log⁡(Ngroup)=α+β⋅log⁡(VneocortexVrest of brain)\log(N_{\text{group}}) = \alpha + \beta \cdot \log\left(\frac{V_{\text{neocortex}}}{V_{\text{rest of brain}}}\right). Group size as a function of relative neocortex volume, nothing else in the model earning its keep. Dunbar’s interpretation was mechanistic rather than merely statistical: neocortical…

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Learn the underlying idea

An equals sign says that the expression on its left and the expression on its right have the same value under the stated definitions and assumptions.

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Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.