Minimum Number of Individuals

Paired bones such as humeri, femora, and temporals appear twice per individual animal (one left, one right). If left and right bones are combined without separating them, the resulting count can be artificially high. For example, 10 left humeri and 2 right humeri indicate a minimum of 10 individuals (because there must be at least 10 left sides present). Failing to account for pairing can result in MNI values that are nonsensically high.

Taphonomic processes (scavenging, weathering, diagenesis) differentially affect skeletal elements. Some bones are more durable and more likely to survive; others are fragile and frequently lost. If a certain element is preferentially destroyed by taphonomic processes, the assemblage will under-represent that element's frequency, leading to underestimation of MNI. Conversely, if humans selectively discard certain elements, their absence may not reflect an actual shortage of animals.

NISP (Number of Identified Specimens) is a simple count of all identifiable bone fragments, regardless of which elements they represent. MNI uses only the most frequently occurring element, correcting for fragmentation. NISP is easier to calculate but heavily influenced by breakage patterns. MNI is more robust but more time-consuming and requires careful anatomical knowledge. Ideally, both metrics should be reported together to provide a fuller picture of the faunal assemblage.

Technically yes, but with caution. Very small samples (< 50 identified specimens) may have insufficient diversity to produce reliable MNI estimates. Sampling error becomes large relative to actual values. It is often better to report NISP or other quantification methods for small samples and reserve MNI calculations for larger, more robust assemblages (> 200 identified specimens).

Juvenile bones are typically more fragile than adult bones and may be under-represented in assemblages due to taphonomic loss. Some analysts separate juvenile and adult MNI counts, recognizing that the juvenile MNI may be underestimated. Alternatively, size-grade distributions can be examined to assess whether juveniles are genuinely scarce in the assemblage or simply under-preserved. Skeletal maturity indicators such as bone fusion and tooth eruption help distinguish age classes.