DNA evidence can be analyzed for genetic markers to determine phenotypes such as hair and eye color, ancestry, and even age estimation. Currently, telomere length is the only genetic biomarker that has been correlated to cell replication and replicative cell senescence--both strong indicators of tissue aging in humans. Unfortunately, while many studies have found a strong correlation between telomere length and age, many data sets show extreme variability, technical assay malfunction, inadequate evaluation of other variables that can impact telomere, altogether conflicting results, or insignificant correlations due to low sample size. Other, non-telomere based methods are problematic, as they often have only the ability to identify newborns or are only viable for specific tissue or cell types, and for most, the effects of outside variables have not been fully evaluated. Thus, telomeres remain the most promising biomarker for age estimation; mechanisms for telomere repeat attrition over time have been well documented. Unfortunately, assays currently used determine mean telomere length of a sample, are not precise or reproducible. New techniques should be robust enough to determine age across a broad spectrum of age ranges, and the effect of other variables (gender, race, disease, etc.), must be explored.
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