# Function: maxGroupSize()

[**lifecycle-kit**](https://jonbogaty.com/lifecycle-kit/api/readme/index.md)

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[lifecycle-kit](https://jonbogaty.com/lifecycle-kit/api/readme/index.md) / [bio-laws](https://jonbogaty.com/lifecycle-kit/api/bio-laws/readme/index.md) / maxGroupSize


# Function: maxGroupSize() {#function-maxgroupsize}


> **maxGroupSize**(`neocortexRatio`): `number`

Defined in: [bio-laws/lifeHistory.ts:169](https://github.com/jbcom/lifecycle-kit/blob/074e4e7b8038d3e2de9eb44c4b5b5aee0ef02b48/src/bio-laws/lifeHistory.ts#L169)

Maximum stable social group size, from neocortex ratio.

Source: Dunbar, R.I.M. (1992). "Neocortex size as a constraint on group size
in primates." Journal of Human Evolution, 22(6), 469-493.

  log10(N) = 0.093 + 3.389 × log10(CR)

CR is the neocortex volume divided by the volume of the REST of the brain —
not by body mass. It runs about 1.5 in small primates and 4.1 in humans,
where this yields 148: Dunbar's number, reproduced from his own regression.

The ported PEER_REVIEWED_LAWS.md gives a linear form (N = 42.2 + 3.32 × CR)
together with an estimator CR ≈ 4.0 × (Brain/Body)^0.25. Neither survives
contact with the paper's headline result: the linear form is bounded near 56
across the entire primate CR range and cannot produce 150 at any input, and
the estimator returns 1.54 for a human where Dunbar measured 4.1. The assay
in lifeHistory.test.ts is what caught it. We implement the log-linear
regression and take CR directly, because there is no defensible way to get
it from body mass alone.

Relevant once companionship exists: how many others a creature can hold
relationships with is a consequence of its brain, not a UI limit.


## Parameters {#parameters}



### neocortexRatio {#neocortexratio}


`number`


## Returns {#returns}


`number`