Retrodeformation techniques and 3D morphometric analysis of an early holocene South American skull (Cuncaicha, Peru)

As a consequence of the taphonomic history, many fossils and relevant specimens present missing parts and post-depositional alterations. For that reason, in spite of the great effort invested in their recovery and preservation during the archaeological excavations, they are left out from the morphometric analysis. Therefore, they cannot be used for discussing human variability and evolutionary processes. This is especially the case for South America, where the early Holocene specimens are scarce, and some of them are incomplete and/or present some changes as a result of post-depositional alterations. We present here the first virtual reconstruction of an early Holocene South American skull that was recovered from the excavations at Cuncaicha rock shelter in the south of Peru (9240-8770 calibrated years BP) [1]. The skull is composed of 20 fragments that were scanned in the Paleoanthropology Department at the University of Tübingen. A virtual anatomical reconstruction was conducted by using Avizo and including skull reference models from the Andes. As the cranial vault presents a strong alteration resulting in a lateral distortion that affects the whole vault shape, retrodeformation techniques were applied for modeling post-depositional changes [2]. In spite of the large degree of completeness of the skull (approx. 80%), there are some missing parts that were estimated by mirroring them from the opposite preserved side of the skull. This allowed conducting 3D morphometric analysis from the whole skull by comparing it with other early and late Holocene specimens from South America (N=500), by taking into account the symmetric component only. Shape changes were studied by running between-groups Principal Component Analysis. The results are discussed together with a previous 2D morphometric study of the facial variation that allowed establishing associations with specimens from Lagoa Santa in Brazil, supporting previous claims of morphological similarities among the early settlers of the continent [3]. Such craniofacial patterns were interpreted as the retention of some ancestral features among some of the early South American populations.