Minimum Number of Individuals (MNI)

The minimum number of individuals, abbreviated MNI, estimates the smallest number of whole animals that could account for the bones identified in a faunal assemblage. Where NISP counts identifiable pieces, MNI translates those pieces into a defensible lower bound on the number of animals by exploiting the fact that each animal has a fixed inventory — only one left femur, two scapulae, and so on. The basic procedure, introduced by Theodore White in 1953 and refined since, takes the most abundant element after accounting for side and age and divides by its frequency in a complete skeleton. As Reitz and Wing explain and Lyman analyzes critically, MNI tames NISP's fragmentation bias but introduces a bias of its own: it depends on how the assemblage is aggregated into analytical units, the so-called aggregation problem.