Lines of Arrested Growth (LAGs)
Definition
Alternating dense and loose concentric rings in bone cortex visible in histological cross-section, analogous to tree rings. Each LAG marks a period of seasonal metabolic slowdown. Ring count estimates biological age.
- Structure
- Alternating dense and loose rings in bone cortex
- Cause
- Seasonal metabolic slowdown
- Use
- Biological age estimation via ring count
- Analogy
- Tree growth rings
Common questions
Why are LAGs more informative in some populations than others?+
Individuals living in strongly seasonal climates lay down clearer growth interruptions than those in stable tropical or captive environments, so ring counts are more reliable where seasonal stress is pronounced.
Does counting LAGs give an exact age?+
It gives an estimate, not an exact figure, because ring deposition can vary with health, nutrition and individual physiology, so the count is interpreted alongside other ageing indicators.
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