Chico river basin
Do you know when the first humans arrived to the Chico river basin?
The earliest evidence of human presence near the Chico river dates back to about 12.800 years.
It comes from a site about 60 km north of this river, La Gruta 1, located near a lagoon that, in general, lacks water.
Where did these first inhabitants come from and how did they live?
It is likely that they came from the north, as other earlier sites have been found in that area.
They were mobile hunter-gatherers, meaning they moved between different places throughout the year.
As in the Santa Cruz river basin, these occupations would have occurred at a time that was more humid than the current one in the area. The images show evidence of ancient beach levels, which show that there could have been more water in the past.
By this time, the presence of a black volcanic glass, called obsidian, has been recovered. Given its small size, it could have been obtained by hunter-gatherers at the source of this raw material located just 12 km to the south, called 17 de Marzo, which we identified in the course of our research. Given the short distance involved, hunter-gatherers could have obtained this raw material in the framework of their usual activities.
What happened next?
After these initial occupations, there was a lack of human presence between 12.000 and 10.800 years ago. From this last date onwards, evidence of human use of this space began to be more abundant and included not only the site La Gruta 1, but also other sites such as La Gruta 2, El Verano cave 1 and La Martita cave 4 (see figures). These last two sites, located approximately 25 km to the northeast and north respectively, were excavated by V. Durán (El Verano) and A. M. Aguerre (La Martita). The occupations of this period correspond, according to the paleoenvironmental data generated by M. V. Mancini and G. A. Brook, to a more humid period. At this time, there is also evidence of the presence of extinct fauna (Mylodontine) in a large eave, La Gruta 3, as shown by the initial surveys and the widening of the occupations carried out together with the team of T. Goebel and K. Graf (Kansas University). The marks it presents are being analyzed to determine whether or not it was used by humans (see figures and the section corresponding to Fauna in Research Lines).
At the southernmost end of the Deseado Massif, in the localities of La Gruta and El Verano, caches of raw material have been found that likely correspond to this period, based on the technological similarities and raw materials from artifacts recovered at this time. The artifacts from these caches were originally left to be used at a later time, something that did not happen. Both caches are primarily composed of high-quality raw material not available in the area, and the source has yet to be identified. Thermal treatment—heating the rocks to improve their quality—was also used on the raw materials. While both caches contain bifacial artifacts (see figure), there are also, particularly in the case of the one found at El Verano, other types of tools. These bifacial artifacts might have served as a reservoir of raw material. Moreover, analysis of the size of the other artifacts indicates that by this time period, hunter-gatherers already knew the Pampa del Asador obsidian source, located more than 100 km to the west. Additionally, by this time, hunter-gatherers were already producing paintings in the area, as evidenced by the findings made by Durán in the El Verano cave (see figure).
Around 8,700 years ago, a period of aridity began at the southernmost end of the Deseado Massif, during which no human occupations were detected. This marks a time when the Massif was either abandoned or used in a way that left no visible archaeological traces. It is precisely during this period of abandonment of the Massif that the first evidence of occupation appears in the basaltic canyons located more than 100 km to the south, which have their mouths iin the middle course of the Santa Cruz river (see Santa Cruz river basin, northern margin).
The southernmost end of the Massif was reoccupied during a wetter period. However, by this time human populations had developed a new method of manufacturing tools, obtaining laminar blanks (see Lithics in Research Lines). According to Aguerre's findings, these tools were very common in the area around 5,500 years ago. The current state of research does not yet allow us to determine if their presence represents a technological reorganization due to changes in the way the space was used, or if it could be the result of the arrival of new human groups who made their tools in a different way. The latter scenario seems plausible given that these are vast areas with low population densities.
The rock art in the south of the Deseado Massif are mostly paintings, as already pointed out by Aguerre and Gradin (figures). The investigations carried out within the framework of our research projects, conducted by A. Acevedo and D. Fiore, have allowed us to locate more sites and attribute some of them to this period, as shown by the dates we obtained directly from them. As Gradin had already pointed out at the end of the last century, the techniques used in the south of the Deseado Massif consist mainly of paintings and, in this sense, are different from those found in the basaltic canyons that flow into the Santa Cruz river, where there are many engravings (see Santa Cruz river basin, northern margin).
This nomadic hunter-gatherer lifestyle continued in the area until shortly before the arrival of the Europeans. During this last period, the ancient inhabitants equipped the landscape, constructing structures used for hunting their prey (see Spatial Analysis – GIS in Research Lines). The fact that these structures are grouped together and that from some of them the nearby lagoon is not visible suggests the use of enclosure and collective hunting techniques, as demonstrated in a study conducted with Vetrisano, Gilio, Cirigliano, and Bianchi.
By these last moments, human populations were occupying not only the Deseado Massif but also the open basaltic spaces located to the south and southwest respectively, as shown by the dates we obtained. In these basaltic spaces, as Gradin pointed out, engravings predominate, made by pecking and/or incisions, although there are also red paintings. In this sense, and as Gradin stated, this art is similar to that of the canyons north of the Santa Cruz river. At this time or perhaps a little time afterwards, ancient inhabitants also made pottery, which in some cases was incised, as shown by the dates we obtained in open spaces located just 12 km south of the Massif, in 17 de Marzo (see Ceramics in Research Lines).
In this area, endscrapers made from industrial glass have also been identified. These tools, which correspond to the contact with the Europeans, indicate the continued use of traditional techniques for processing animal hides, likely for the production of quillangos or cloaks, as noted in historical records (see Glass in Research Lines).