Faunistic analysis in the Chico river basin

Archaeofaunal studies are currently being carried out at several sites located south of the Deseado Massif. These analyses aim to investigate the subsistence of hunter-gatherers in relation to environmental variations and the movements of the human groups that frequented these spaces.

Our data, combined with those previously obtained by Aguerre and Durán, indicate that the guanaco would have been the main resource used by human groups in this area.

Furthermore, in sites in this area such as La Gruta 3, remains of extinct animals such as Mylodontino (a species of giant sloth) have been recorded, dating back at least 9.500 years. We are currently investigating both the reasons why the remains of this animal were found in this site, and whether or not these animals were processed by hunter-gatherer groups. To do this, we make 3D models of the bones belonging to specimens catalogued as extinct fauna, which allow us to make systematic measurements of the traces observed on the bone surfaces. In this way, we build a catalogue of traces and measurements that in the future will allow us to evaluate the existence of processing of Mylodontino by hunter-gatherer groups in this space.

3D models as an exploratory methodology in the analysis of linear marks on bone remains

This technique determines the geometric properties of an object and its position from photographs. It is an easy-to-use tool and is partially automated. It is also inexpensive compared to other specialized tools.

3D Model Assembly Process

Once the photographs (A) were taken, they were loaded into the 3D modeling program. The processing began with the alignment of the photographs to obtain a sparse point cloud. Then the dense point cloud (B) was built and scaled and, based on the depth maps, the 3D solid model, the 3D model with texture and orthophotographs (C) and the DEM (D) were built. As a result, we were able to obtain 3D models and DEM models that can be measured in any Geographic Information System (E).

1) Photo alignment and sparse cloud construction

  • Automatic camera optimization
  • Gradual elimination of sparse matching points

2) Dense cloud construction

3) Elimination of low confidence points if any

4) Model scaling

5) 3D model construction

6) DEM construction

7) Orthophoto construction

On the rib of Milodontino with possible cut marks: References: Red rectangle top right: sector where the marks are located. From right to left (1,2,3,4): common photos with projection of leftovers showing at least four linear, superficial, oblique, medium and short length marks (5) root mark of a plant.

Left: Top solid 3D model and bottom DEM of footprint 4 and root mark 5.

Right: A) Measurements of print 4: "V" profile with small ridges on its sides. In this case, its middle section shows two "V" profiles, similar to what we would expect from a double trace when trying to remove the flesh from the bone. B) Measurements of the root mark: groove left by a root that was removed in the laboratory to compare the previously measured profiles. The valley of this mark, unlike the other prints, is deeper, with a very clean "U" profile and no ridges on its sides, which differentiates it from a mark made by a cutting instrument.

Median phalanx of Mylodontine: taking photographs with shadow projection allowed us to see a short, deep, transverse, linear imprint on the palmar surface of the distal epiphysis. Accompanied by thinner imprints on the opposite surface of the phalanx.