El estudio arqueológico del proceso coevolutivo entre las poblaciones humanas y las poblaciones de guanacos en Patagonia Meridional y Norte de Tierra del Fuego

L'HEUREUX G. L.

British Archaeological Reports (BAR,). Publishers of British Basingstore Press

Lugar: Oxford; Año: 2006 p. 275

1-84171-901-3

The aim of this study is to present a coevolutionary perspective on the interaction between human and guanaco (Lama guanicoe) populations in Magallania, i.e. the area at both sides of the Magellan strait comprising the southernmost part of continental Patagonia and the north of Tierra del Fuego in southern South America (Argentina and Chile), during the last 12,000 14C years BP. The methodological approach adopted combines the use of morphological, paleoenvironmental, zooarchaeological, and technological data. Coevolutionary interactions between species may result in microevolution in each taxon. Coevolution is defined here as reciprocal selective pressures that operate to make the evolutionary change of one taxon partially dependent on the evolutionary change of the other. Consequently, coevolution at the microevolutionary level is expected to mirror the long-term interaction between populations of at least two different species throughout evolutionary time. It is expected that guanacos and humans, which established a consistent, long-lasting and stable predator-prey relationship since the Late Pleistocene until recent historical times, may have mutually influenced their relative fitness through time. Due to the evolutionarily short time period involved (about 2,200 generations of guanacos and 440 generations of humans), it is expected that the implied coevolutionary changes mostly affected behavioural traits. However, some morphological traits could also be involved. In the case of guanaco populations, they were probably due to size-selective predation. Taking into account these general expectations, the main research objectives were: a) to assess the temporal and spatial variation in limb bone morphology in skeletal samples of guanaco recovered at several archaeological and one paleontological sites of the study area; and b) to detect covariations between morphology and paleoenvironmental, demographic, zooarchaeological and technological variables. In order to measure guanaco bones an osteometric guide was elaborated, adapting available measurements developed for other South American camelids and ungulate genera to the particular anatomic features of this species. Most measurements describe the proximal and distal epiphyses of humerus, radioulna, metacarpal, femur, tibia and metatarsal, but some complete bones were also measured (astragalus, calcaneus, first and second phalanx). Univariate and multivariate statistical techniques were applied (ANOVA; Discriminant Analysis —DA—; Principal Components Analysis —PCA—; Hierarchical Clustering —IC— and Multidimensional Scaling —MDS—) to investigate the patterns of variation in both, size and shape. The initial (i.e. Late Pleistocene) body size of guanaco populations in southern Patagonia and Tierra del Fuego, which conformed a continuous surface of emerged land until the formation of the Magellan strait ca. 8000 14C years BP, was statistically undifferentiated. However, two different trends at both sides of the Magellan strait have been detected during the Holocene: in Tierra del Fuego, there were no significant morphological changes through time in the sampled guanaco populations, but in continental Patagonia there was a marked reduction in size between Late Pleistocene and Early Holocene samples, fluctuations in size and shape during the Middle Holocene, and a further deceasing in size during the Late Holocene.