An international study, in which the University of Granada (UGR) is participating as part of the ProyectORCE project, has obtained new data on the Prehistoric humans who inhabited the Guadix-Baza basin, thanks to an analysis of the teeth of herbivorous animals such as mammoths, hippopotamuses, rhinoceroses, horses, deer, and bison
This study, in which the University of Helsinki (Finland) is also participating, reveals that our ancestors could only inhabit this area when Mediterranean ecosystems provided extra productivity, since these first hominids required a high amount of energy, and resources there were insufficient during the cooler and drier climatic phases
The first humans to inhabit the Guadix-Baza basin (Province of Granada) during Prehistory (from 1.5 million to 400,000 years ago) looked for areas of high vegetation in order to survive, but they could only inhabit this area when the productivity of Mediterranean ecosystems was especially abundant, since these ancestors required a high amount of energy, and resources there were insufficient during the cooler and drier climatic phases.
These are the main conclusions drawn from a study led by researchers from the Universities of Helsinki and Granada and published in the journal Quaternary Science Reviews. This was an interdisciplinary, international study in which, as well as the aforementioned universities, the Catalan Institute of Human Paleoecology and Social Evolution (IPHES, Tarragona) and the Universities of Zaragoza, Barcelona, Salamanca, Complutense de Madrid, and Tübingen (Germany) also participated. The work was conducted within the framework of the ProyectORCE project, coordinated by the UGR and financed by the Junta (regional government) of Andalusia.
4.5 million years of history reflected in teeth
To arrive at these conclusions, the scientists analysed the teeth of herbivorous animals-such as mammoths, hippopotamuses, rhinoceroses, horses, deer, and bison-found at the different archaeological sites at Orce (Granada). This is the first study to analyse the faunal evolution and the ecological changes that took place over a period of four million years in the Guadix-Baza basin, which is located in the Granada Geopark.
Teeth are anatomical structures that are directly related to diet. To determine the significance of the main types of vegetables consumed in that epoch, two techniques developed by Mikael Fortelius (lecturer at the University of Helsinki and Visiting Scholar at the UGR) were applied to a dozen sites that date back as far back as 4.5 million years ago (Baza-1 site) to as recently as 400,000 years ago (Solana del Zamborino site, Fonelas). The two techniques involved studying patterns of wear in the animal teeth and the structural characteristics of their dental remains (known as the "ecometric method").
On the one hand, dental wear is linked to the nature of the food consumed by the animal: the harder it is (and the lower the consumption of vegetables), the greater the deterioration of the teeth. On the other hand, the presence or absence of certain dental functional traits correlates closely with rainfall and, above all, with primary productivity-that is, with the quantity and quality of plant matter available to herbivores.
Habitat type revealed
One of the great debates that have surrounded the first human settlement of the European continent is the type of habitat that our oldest ancestors occupied. Some scholars claim that the first humans went out "in pursuit" of the habitat of origin-that is, the savannah. But the results of this study, led by Juha Saarinen of the University of Helsinki, show that, in fact, these primitive groups lived in habitats very similar to those still in existence today in much of the Iberian Peninsula: Mediterranean woodland. It is well known that the climate associated with these ecosystems is extremely seasonal, with summers dominated by a persistent drought, in which productivity falls to a minimum, especially when coupled with extended autumn and spring droughts.
The maximum productivity is found at Solana del Zamborino (Fonelas), a very interesting archaeological site dated to approximately 400,000 years ago, which coincides with one of the warmest and most humid periods of the last two million years. Following this, in terms of productivity, is a paleontological site, Baza-1, in which, due to its age (4.5 million years old), the presence of hominids is not to be expected.
At the opposite extreme are the paleontological sites with the lowest productivity: Huélago (2.5 million years), Fonelas-P1 (2 million years), and the Orce-based sites of Fuente Nueva-1 (2.2 million years) and Venta Micena (1.6 million years). The likelihood of finding evidence of a human presence at these sites is very low or inexistent. In between, with high productivity, are the emblematic sites of Barranco León (1.4 million years old) and Fuente Nueva-3 (1.2 million), the oldest locations with evidence of a human presence in the western part of Europe.
Human presence is also documented at Huéscar-1 (1 million years) and Cúllar-Baza-1 (Cúllar, 800,000 years) albeit on a very small scale. Finally, there are other sites that could likely have been home to our ancestors but that, for the moment, yield no clear evidence: Barranco del Paso (Orce, 1.8 million years old) and Mencal-9 (Pedro Martínez, 1.7 million years). Therefore, this study constitutes a hugely significant methodological contribution in the quest for locations that would potentially have been habitable for the very first Europeans.
Humans, major energy consumers
But why did our most distant ancestors require such productive habitats? "In the first place, because we are a very gregarious species that needed to live in relatively large groups, possibly of more than 30 individuals", explains Juan Manuel Jiménez Arenas, the director of ProyectORCE and a researcher from the UGR's Department of Prehistory and Archaeology.
"This gave us an important evolutionary advantage in relation to, on the one hand, inbreeding (probably one of the triggers for the disappearance of Neanderthals) and, on the other, the presence of predators. Likewise, social cohesion would contribute to survival in a complex and conflictive environment. In addition, humans have tremendously large brains relative to our body mass. Remember that this organ consumes an extraordinary amount of energy for its low weight (just 2% of total body mass vs. 20% of energy consumption in today's humans)", notes Jiménez Arenas.
Furthermore, the inability to produce fire or work with it would render certain foods of plant origin inedible. Lastly, the lithic technology or tools available to the first settlers of the European continent did not lend themselves to making intensive use of the available resources. "To exemplify this, our study reveals that our ancestors could not currently live in the Orce area. Hence, given the means to which they had access, the earliest settlers of Europe could not cope with an overexploitation of the territory, as is the case today. Therefore, it was Nature that determined the presence of our ancestors-it was not they who imposed themselves on Nature", concludes Jiménez Arenas.
Bibliography:
Saarinen J, Oksanen O, Žliobaitė I, Fortelius M, DeMiguel D, Azanza B, Bocherens H, Luzón C, Solano-García JA, Yravedra J, Courtenay LA, Blain H-A, Sánchez-Bandera C, Serrano-Ramos A, Rodríguez-Alba JJ, Viranta S, Barsky D, Tallavaara M, Oms O, Agustí J, Ochando J, Carrión J, Jiménez-Arenas JM (2021), 'Pliocene to Middle Pleistocene climate history in the Guadix-Baza Basin, and the environmental conditions of early Homo dispersal in Europe', Quaternary Science Reviews 268: 107132.
Image captions:
Reconstruction of the palaeoenvironment that would have been found in Orce 1.5 million years ago. Recreation by Mauricio Antón from data derived from the Georgian site of Dmanisi
Juha Saarinen, main author of the work, at the Venta Micena site (Orce, Granada) during the 2018 campaign. Photo by Susana Girón
Evolution of productivity over the last 4.5 million years from the main paleontological and archaeological sites of the Guadix-Baza basin. The full squares correspond to sites where evidence of a human presence has been found. The blank squares represent those without evidence of a human presence. The section of the graph shadowed with grey lines indicates the range of productivity where the probability of human presence is low. The dotted lines represent the interval where the appearance of a human presence is highly probable. CG-B = Guadix-Baza Basin. Modified from Saarinen et al. (2021)
The present-day landscape at Orce. Photo by Susana Girón
