Following the Tracks of the First South Americans
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Evo Edu Outreach (2011) 4:205–217 DOI 10.1007/s12052-011-0335-4 ORIGINAL SCIENTIFIC ARTICLE Following the Tracks of the First South Americans Cristina Bayón & Teresa Manera & Gustavo Politis & Silvia Aramayo Published online: 5 May 2011 # Springer Science+Business Media, LLC 2011 Abstract In this article, a summary of the geologic, presence; the third one shows faint evidences (one human paleontological, and human history of an area of the trackway and two isolated footprints), and in the last one Atlantic coast in the Pampean plain, Argentina is discussed. the hunter–gatherers are fully represented as a well- This area presents very interesting characteristics. On the established population on the Pampean coast during the one hand, the area includes the Monte Hermoso cliffs Early Holocene, registered at La Olla and Monte Hermoso I studied by Charles Darwin in 1832, which compose the set sites. In this way, the sites summarized in this work allow of localities related to the development of the theory of the reconstruction of four remarkable evolutionary scenar- evolution. On the other hand, in the referred area, an ios in South America, as regards landscapes, fauna extraordinary amount of human and Pleistocene mammal associations, and human population. footprints are registered. Also in that section, four dia- chronic stages have been registered which depict the Keywords Fossil mammal footprints . Pleistocene evolutionary scenario during the last five million years. megamammal extinctions . Early peopling of South Four paleontological and archeological sites are described, America . Holocene coastal adaptations showing the palaeoenvironmental changes that occurred there regarding fauna associations and human settlement. The first scenario is found at Monte Hermoso cliff, whose Introduction sediments contain fossil remains of the autochthonous South American fauna. The second scenario shows a The aim of this article is to present a summary and a remarkable change in the drainage system where the fauna panoramic view of the geologic, paleontological, and is composed of immigrated taxa due to the Great American human history of an area of 30 kilometers on the Atlantic Biotic Interchange. Both last scenarios show human coast in the southwest of the Argentinean Pampean plain between 32º and 40º south latitudes (Fig. 1). This is an area on the coast in which the natural outcrops and the discovery C. Bayón (*) of fossils, human bones, tools, and footprints from animals Departamento de Humanidades, Universidad Nacional del Sur, and humans illustrate the evolution of life in the region 12 de octubre and San Juan, 8000, Bahía Blanca, Argentina from the Upper Tertiary to the Middle Holocene. This long e-mail: [email protected] history of five million years was recorded in an extraordi- : nary way in four diachronic moments which reflect T. Manera S. Aramayo different scenarios with different environmental conditions Departamento de Geología, Universidad Nacional del Sur, San Juan 670, and protagonists. Each of them shows the species typical of 8000, Bahía Blanca, Argentina that moment, within different landscapes, shaped by the climatic changes. Human beings appear in the last two G. Politis scenarios; first, in Pehuen Co site at the end of the CONICET-INCUAPA, Facultad de Ciencias Sociales, UNCPBA, Av. del Valle 5737, Pleistocene, leaving a still weak signal; and then as strong 7400, Olavarría, Argentina evidences in the sites of La Olla and Monte Hermoso I in 206 Evo Edu Outreach (2011) 4:205–217 Fig. 1 Eastern Pampean Region map: archeological sites mentioned Amalia; 15 Lobería 1. Limits of the studied area. in the text: 1 Arroyo Seco 2 site; 2 El Guanaco 1 and 2 sites; 3 Paso Coast in the Late Pleistocene (ca. 12,000 14 C yrs BP; Otero 5; 4 Campo Laborde; 5 La Moderna; 6 Los Helechos; 7 Cerro La China 1,2, and 3; 8 Cerro El Sombrero; 9 Cueva Tixi; 10 taken from Flegenheimer et al. 2007). Current coast Burucuyá; 11 Los Pinos; 12 La Brava; 13 Cueva El Abra; 14 La which the occupation of the sea coast by ancient Pampean ically important changes that occurred, the same formation hunter–gatherer groups during the Early and Middle conditions and erosive processes were amazingly repeated Holocene is clearly recorded. to allow the preservation and exposition of footprints of The sector of the coast analyzed in this review is the different origin and age. edge of a plain located between the Ventania hill range and A footprint or ichnite is a trace left on a soft substratum the sea (Fig. 2). These hills act as dispersion centers of the by an organism moving on it. However, in order to be pluvial water-forming rivers which flow from the hills of preserved as a fossil footprint or ichnofossil, certain special Ventania towards the Atlantic Ocean. The coastal area conditions must be present. The substratum should be wet where these four scenarios are recorded is closely for the footprint to be imprinted; afterwards, it has to dry connected to the evolution of the lower valley of the Sauce and be covered with sediment of different composition Grande River, which is the most important river in the within a brief period of time. After thousands or millions of southwest of the Buenos Aires province. Nowadays, the years, this substratum turns into a rather consolidated rock. river course is obstructed by a chain of coastal dunes, The thinner the sediment grains, the better the footprint causing it to divert to the east, forming a small lake and details are preserved. Also, the differences in lithology flowing parallel to the line of dunes for 30 kilometers until allow the formation of a weakness plane through which the reaching the sea. rocks can be separated by the means of erosion, permitting The high number of either human or animal footprints is the ichnite to be exposed and studied. the most remarkable aspect of this group of archeological In the sector of the Atlantic coast summarized here, the and paleontological sites. In spite of the extensive span of presence of ichnites is complemented with another type of time considered and the geographic, climatic, and biolog- information; namely, synchronic and diachronic, which Evo Edu Outreach (2011) 4:205–217 207 Fig. 2 Study area allows a more precise reconstruction of the environmental thinking as his much more famous visit to the and human history. These elements are outcrops exposed Galapagos Islands three years later! along many kilometers with Tertiary and Quaternary sedi- Fifty years later, that interest in Monte Hermoso cliff ments, containing vertebrate fossils and stone, bone, and was revived by Florentino Ameghino, who considered that wooden tools of human populations who occupied the there was enough proof in the Monte Hermoso cliff to region since the Late Pleistocene. demonstrate the evolution of different mammals, including human beings. In 1887, he stated that Historical Background Lo que aumenta extraordinariamente la importancia del yacimiento de Monte Hermoso, es la presencia del The paleontological and archeological importance of the hombre conjuntamente con una fauna singular, reve- area treated here—mainly the Monte Hermoso cliff known lada tanto por algunos pedernales y huesos tosca- today as Farola Monte Hermoso—has been recognized mente tallados cuanto por la existencia de fogones en since the nineteenth century. In October 1832, Charles distintos niveles de la barranca, engastados en capas Darwin found the first fossil remains recovered from the de arcilla, de los que con trabajo he podido arrancar lower layers of that fossiliferous locality, stratigraphically fragmentos para llevar al Museo de La Provincia en named Monte Hermoso Formation. A few days before, he La Plata [The importance of the Monte Hermoso had found in Punta Alta, about 50 kilometers to the west, deposit is the presence of man, together with such a fossil remains of large mammals that caught his attention singular fauna, both revealed in flints and bones remarkably (Megatherium, Mylodon, Toxodon). On Monte grossly carved, the existence of campfires at different Hermoso cliff, he collected, along with some large mammal cliff levels and mounted in clay layers from which I bones, several rodent remains including one of a cavid. was able to take fragments to take to the Museo de La Regarding this fossil, Eldredge (2009) points out: Provincia en La Plata] (Ameghino 1887: 5/6). With the Monte Hermoso fossil cavy, Darwin had Between 1906 and 1907, he made public the Tetrapro- direct evidence of the existence of an extinct species thomo argentinus, which he considered to be an ancestor of that had been replaced by a close relative still alive humans. The remains found were a femur and an atlas; the today. There can be no way of concluding with first one was collected by Carlos Ameghino, while the atlas certainty that Darwin had by then become a ‘trans- belonged to the Museo de La Plata collection (Pupio et al. mutationist’ but it is clear from his notes that he was 2009). Finally, in 1910, he published the finding of the actively contemplating the possibility as early as late oldest industry he recognized “la Industria de la Piedra 1832. Thus, I cannot help but think of Bahia Blanca Quebrada” (the broken stone industry), which he assigned as being as important to the development of Darwin’s to the Upper Miocene. During the Congreso Internacional 208 Evo Edu Outreach (2011) 4:205–217 de Americanistas, held in Buenos Aires in 1910, the Monte ary stage called Montehermosan Stage/Age (Marshall et al. Hermoso cliff was visited by Aleš Hrdlička and Bailey 1983). Actually, this site is the archetype of this biostrati- Willis, who rejected Ameghino’s propositions. The debate graphic unit. Although most of the fossils preserved here was fierce, and the site was repeatedly visited to clarify are bones, which have helped define the Stage/Age, there different aspects, such as stratigraphy and technology.