Minimum Number of Individuals (MNI)
Definition
The smallest number of distinct individuals required to account for all skeletal elements present in an assemblage. Determined by identifying the element and side that appears most frequently, accounting for age-class and size differences. Used in the Buikstra-Ubelaker Walker 2008 revision for commingled and mass-grave assemblages.
- Key metric
- Lower-bound count of individuals in a commingled or fragmented skeletal assemblage.
- Calculated from
- The most frequently occurring element and side (e.g., the most common left femur count).
- Common contexts
- Commingled remains, mass graves, disaster victim identification, charnel pit excavations.
Common questions
How do you calculate the Minimum Number of Individuals (MNI)?+
MNI is calculated by identifying the skeletal element (like a left femur or right humerus) that appears most frequently in the assemblage. That count becomes the MNI, because you need at least that many people to account for all those repeated elements. It's a bottom-up count: if you find 7 left femurs, you had at least 7 individuals.
Why is MNI useful in forensic investigations?+
When remains are commingled (mixed together) or fragmented, you often can't count complete skeletons. MNI gives you a defensible lower-bound body count. It's essential in mass graves, charnel pits, and disaster victim identification (DVI) to tell the court how many people were likely present.
Does MNI account for differences between people?+
Yes. Forensic anthropologists consider age-class and size differences when determining MNI. For example, if you find two femurs that are dramatically different sizes, they likely belonged to different individuals, even if they're both left femurs. This refines the count beyond simple element frequency.
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- Commingled Remains
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- DVI (Disaster Victim Identification)
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