Bones can reveal fixed biological characteristics. Which of the following are considered fixed evidence?

• A. Height, age, diet, illness, and injury
• B. Eye color and hair color
• C. Sex, ancestry, and genetic makeup
• D. Bone density and bone mineral content

Answer: (C)

Fixed characteristics are traits that come from our genetics and remain constant over a person’s life, making them reliable anchors in skeletal analysis. Sex, ancestry, and genetic makeup fit this idea because sex is determined by pelvic and skull morphology patterns shaped by biology, ancestry reflects ancestral lineage encoded in DNA and reflected in skeletal traits, and genetic makeup is fundamentally the DNA that defines an individual’s inherited traits. While other options can change or be influenced by growth, aging, health, or environment—such as height (grows and changes with age), diet or illness (can alter bone condition), or bone density (varies with age and health)—they aren’t fixed attributes. Eye color and hair color aren’t reliably inferred from bones, and bone density measures can fluctuate, so they don’t represent stable, unchanging traits.