How can non-metric cranial traits be used in ancestry estimation, and what is a major caveat?

• A. They are used to determine exact population membership; caveat: universal applicability.
• B. They are used to measure skull volume; caveat: measurement error.
• C. They are used to estimate age; caveat: changes with pathology.
• D. They are used to assess probabilistic population affinity; caveat: observer bias and population-specific biases; should be used with caution and with other data.

Answer: (D)

Non-metric cranial traits are qualitative features scored on shape and contour that reflect inherited variation, and they’re used to estimate probabilistic population affinity rather than assigning exact population membership. They help build a likelihood of where ancestry may lie, recognizing that no single trait defines a population. A major caveat is that judgments can be swayed by observer bias and by population-specific biases—the way traits are scored and the reference samples used can shift results, so these data must be interpreted cautiously and in conjunction with other information.