«It’s eight in the morning, seven in Castroforte del Baralla. There are significant traffic delays at the entrance to Vetusta from Barataria ».
While the engines of our cars roar, in the next three minutes of radio we hear terms such as environmental movement, sustainable development, global warming, greenhouse gases, etc. All indicate an apparent concern for a battered planet. At least from a part of the world that is tremendously urbancentric and increasingly detached from our common home, the Earth.
But how did the first inhabitants of the Iberian Peninsula relate to each other? 1.4 million years with their surroundings? What type of vegetation were found? Similar or different from East Africa, your homeland? What do herbivore teeth tell us about it? And finally, were they able to survive in a changing climate and ecological scenario?
Plants, factories of life
Naturally, plants transform the energy of the light into chemical energy. However, animals, including humans, depend on energy stored in other living things. Primary consumers, herbivores, directly from the plants. And the secondary ones, the carnivores, through those. We are in an intermediate point since we are characterized by having an omnivorous diet.
Therefore, a key factor for the sustainability of the different networks of living organisms will be the ability to take advantage of the energy stored by plants. However, not all types of vegetation are equally productive. For example, savannas are more so than Mediterranean forests and scrublands. In addition, productivity is more homogeneous in the former than in the latter.
And what about our ancestors?
We know very little about the physical appearance of the first humans who arrived on the Iberian Peninsula. They were smaller, on average, than us (45 kg), their brains smaller (700 cm³) and their teeth relatively large. Of course, they moved in a very similar way to ours since their limbs were similar.
What we do know well is its ability to carve stone. They made: sharpened flakes to process herbivore muscle bundles; stronger blocks of rock to fracture bones in search of energetic bone marrow; multifunctional tools that present alterations that indicate work on vegetables; and the spheroids found in the deposit of Leon ravine (Orce, Granada, Spain), stones rounded by expert hands, configured to fracture, denoting considerable planning and psychomotor skills.
Now, if the first humans who arrived in the Iberian Peninsula had encountered a climate like the present, they would not have had a chance to survive because the current lack of rainfall – less rainfall less primary productivity – is a limiting factor. The good news is that the first inhabitants of Orce came from a significantly different climate than today.
Sabana no, thank you: Mediterranean forest
The teeth are burned to the foods that the organism that carries them can process. Thus, carnivores have pointed and sharp teeth. Herbivores, for their part, show pieces with more complex chewing surfaces to reduce the size of plant fibers. Among the latter, those species and populations whose diets involve greater wear include reinforcing structures in their teeth to delay deterioration. The study of the shape and wear of the teeth of herbivores allows us to characterize the primary productivity and the type of vegetation and climate at a given time and place.
Thus, in a recently published work we have proposed that the predominant vegetation type during the last two million years in the basin of Guadix-Baza it was the Mediterranean forest and scrub. Therefore, it is ruled out that humans came to the Iberian Peninsula ‘chasing’ their original ecosystem, the savanna.
This typically Mediterranean scenario was characterized, as today, by a changing climate, which fluctuated thanks to the action of a section that has two main gear systems: the Earth’s axis of rotation and the orbit around the Sun. know how Milankovitch cycles.
In general terms, the climate has alternated between glacial phases (colder and drier) and interglacial phases (warmer and more humid). These meteorological changes, especially the greater or lesser rainfall, imply, for the Guadix-Baza basin, the predominance of very wet and dry Mediterranean vegetation.
And these alternations are detected in the Orce Basin Archaeological Zone. In Barranco León (1.4 million years) and Fuente Nueva-3 (1.2 million years), two deposits with human presence, rainfall and productivity are relatively high. Alternatively, Venta Micena (1.6 million years) and Fuente Nueva-1 (2.2 million years) indicate more rigorous climatic conditions and a productivity so low that they would be incompatible with human presence.
Why did our ancestors need high primary productivity?
The first humans to arrive on the Iberian Peninsula were omnivorous and strange beings in the Mediterranean forests. And they had to be integrated into different ecosystems than the original ones in East Africa, with less productive vegetation types and more extreme yielding peaks and valleys. Thus, these factors were key in their lives.
From the point of view of the energy required to survive, we spend approximately what is expected for a non-human primate of similar body mass. For example, the Hadza, today’s hunter-gatherer living in northern Tanzania, weigh 46.4 kg and consume 2,212 kcal per day (averages for adults of both sexes).
Now, we are a very gregarious species that must have lived in relatively large groups, possibly greater than 30 individuals. This would give us an important evolutionary advantage to deal with inbreeding and the presence of predators. The counterpart is that being “many” the total energy demand increases.
On the other hand, many vegetables need to be cooked to become digestible and palatable. But it must be taken into account that the populations that inhabited Europe 1.4 million years ago (and until approximately 400 thousand years ago) did not have the capacity to generate and control fire. Therefore, its food spectrum is reduced.
Thus, it is not that humans need extra energy for the survival of each individual. We require it because we are tremendously social and, in addition, as the technology of our ancestors did not allow us to overexploit natural resources, we could only survive when the environment gave us that abundance in the form of greater plant wealth and therefore with extra energy. And that was provided by the Mediterranean area, although only in the wettest periods. In the driest, they would move to other scenarios seeking greater productivity.
Our ancestors were not environmentalists, but they treated the planet as their home.
Juan Manuel Jiménez Arenas is Professor of the Department of Prehistory and Archeology / University Institute of Peace and Conflicts, University of Granada
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