Identification of rib number and assessment of intercostal variation at the sternal rib end.

A technique for the identification of anatomical rib number is presented here. Preliminary tests indicate that with experience, percent accuracy for identification may approach 100%. This technique was then applied to a skeletal collection where rib number was not documented in order to determine the effects of intercostal variation on the application of rib four age-at-death estimation standards to other ribs. Spearman rank correlations between rib four and ribs three through nine range from 0.89 to 0.91. No significant differences were found between ribs conforming to or deviating from the phase observed on rib four. There is a significant proportion of deviations falling below the phase set by rib four, however these deviations are not statistically associated with rib number and are usually within one phase. These results indicate that rib four standards can be cautiously applied to other sternal ends when rib four is not preserved.

Evaluation of morphological and histological adult skeletal age-at-death estimation techniques using ribs.

Adult age-at-death estimation standards were applied to an independent sample (N = 50, 55) of documented ages 17.5 to 95 years. Estimates derived from the sternal rib end morphological and from the cortical rib histological techniques were compared with each other and to the documented ages. Comparisons to the documented ages reveal no statistically significant differences between the techniques. However, the comparison of each individual's estimates show a poor correlation (r = 0.54) despite the equal performance of the age estimations on the entire sample. Averaging of the two rib age estimates results in an estimate with a stronger Pearson's r (0.86) and a lower standard error of the estimate (7.5 years).

Technical note: improved DNA extraction from ancient bones using silica-based spin columns.

We describe a simple method for extracting polymerase chain reaction-amplifiable DNA from ancient bones without the use of organic solvents. Bone powders are digested with proteinase K, and the DNA is purified directly using silica-based spin columns (QIAquick3, QIAGEN). The efficiency of this protocol is demonstrated using human bone samples ranging in age from 15 to 5,000 years old.