Intrataxonomic variability in metapodial and femur bone density related to age in guanaco (Lama guanicoe). Zooarchaeological and taphonomical implications

M. A. GUTIÉRREZ; C. A. KAUFMANN; M. GONZÁLEZ; A. MASSIGOGE; M. C. ÁLVAREZ

JOURNAL OF ARCHAEOLOGICAL SCIENCE

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 2010 vol. 37 p. 334 - 344

0305-4403

The aim of this paper is to present new information about bone mineral density variability in guanaco (Lama guanicoe), a South American wild camelid; while taking into account its ontogenic development. The importance of considering intra-taxonomic variability in bone density related to age for constructing zooarchaeological indices is also discussed. The results presented here were developed from a large sample of metacarpals (N= 46) and femurs (N= 45) of modern guanacos, ranging in age from ca. 6 months of gestation to 12 years. Bone structural densities were measured using a biphotonic X-ray densitometer, DEXA method, Norland EXCELL and the obtained bone mineral content (BMC) of each scanned portion or complete element was divided by its volume, which was obtained independently by water displacement. Our results indicate that the bone density of each anatomical unit is highly variable, even between individuals of the same species and similar age. Moreover, this data shows that the density ranges of different skeletal elements can overlap, suggesting that it is not possible to predict that a certain element is always denser than another. Consequently, our results question the validity of bone density indices currently used in zooarchaeology that assume invariable BMD values for each skeletal element and a fixed rank order for all of them within each species.