The first European hominids

One of the most important controversies about human evolution and expansion is when and by what route the first hominids arrived in Europe from the African continent. Now, geological dating of the sites in Orce (Baza basin, Granada, Spain) places the human remains found in this area as the oldest in Europe, at approximately 1.3 million years old.

These results reinforce the hypothesis that humans arrived in Europe from the south of the Iberian Peninsula, through the Strait of Gibraltar, rather than going around the Mediterranean via Asia.

The work, led by Lluís Gibert, researcher and professor at the Faculty of Earth Sciences at the University of Barcelona (UB), has included the participation of researchers from the Berkeley Geochronology Center and Murray State University in the United States, both institutions.

The new dating is based on analysing the palaeomagnetism of an area in the Orce region, which had never been sampled before and which has been protected from the erosion that this basin has suffered over the years. This technique is a relative dating method based on studying the reversal of the planet’s magnetic poles due to the internal dynamics of the Earth. These changes do not have a specific periodicity, but are recorded in the minerals and allow time periods to be established from the different magnetic events.

These new data are very precise thanks to the long sedimentary sequence that emerges in Orce. “The uniqueness of these sites is that they are stratified and within a very long sedimentary sequence, more than eighty metres long. Normally, the sites are found in caves or within very short stratigraphic sequences, which do not allow you to develop long palaeomagnetic sequences in which you can find different magnetic reversals,” says Lluís Gibert.

The researchers have been able to identify a magnetic polarity sequence “with five magnetic events that allow the three sites in Orce with human presence to be placed between the Olduvai and Jaramillo subchrone, that is, between 1.77 and 1.07 million years ago,” explains the researcher. They have subsequently applied a statistical age model to precisely refine the chronology of the different stratigraphic levels with a margin of error of only 70,000 years. The result of this innovative methodology is that the oldest site with human presence in Europe would be Venta Micena with an age of 1.32 million years, followed by Barranco León, with an age of 1.28 million years and finally Fuente Nueva 3, with an age of 1.23 million years. “With these data, the other major site on the peninsula, Sima del Elefante in Atapuerca, would be relegated to second place, far behind Orce, between 0.2 and 0.4 million years older,” adds the researcher.

To complete the dating, the authors of the study have also analysed the remains of the fauna found in the different sites in Orce, since this is different depending on the period, and they have compared it with that found in other sites from the early Pleistocene located in other parts of Europe.

In this sense, the work presents a detailed analysis of the micromammals and large mammals from all the sites in Orce, carried out by the expert Robert Martin, based on the paleontological collections stored in the Museum of the Miguel Crusafont Catalan Institute of Paleontology (IPS) in Sabadell. “The results show that the small and large fauna of Orce is more primitive than, for example, that of the Sima del Elefante, where the evidence shows that the rodent Allophaiomys lavocati is more evolved than the Allophaiomys recovered from the sites in Orce,” explains Gibert.

Another relevant indicator of the age of the Orce sites is the absence of the ancestors of pigs. “They are animals that are considered Asian immigrants and that have not been found in any European site between 1 million and 1.5 million years old, while they have been found in the Sima del Elefante, supporting that the Orce fauna is older,” explains the researcher.

This new dating would be added, according to the researcher, to other evidence that would tip the balance in favour of the colonisation of Europe through the Strait of Gibraltar, instead of the alternative route: the return to the Mediterranean via Asia, such as for example “the existence of a lithic industry with similarities with those found in the north of the African continent and also the presence of remains of African fauna in the south of the peninsula, such as those of Hippopotamus, found in the Orce sites, and those of Theropithecus oswaldi, an African primate similar to a baboon, found in the Victoria Cave, a site near Cartagena (Murcia), which do not exist anywhere else in Europe”.

“We also support the hypothesis,” the researcher adds, “that they arrived from Gibraltar because no older evidence has been found in any other site along the alternative route.”

With these results, the researchers point to a “diachronism” between the oldest occupation of Asia, 1.8 million years ago, and the oldest occupation of Europe, which would be 1.3 million years ago, so that African hominids would have arrived in southwestern Europe more than 0.5 million years after leaving Africa for the first time approximately 2 million years ago. “These differences in human expansion would be explained by the fact that Europe is isolated from Asia and Africa by biogeographic barriers that are difficult to overcome, both to the east (Bosphorus Strait, Dardanelles, Sea of ​​Marmara) and to the west (Strait of Gibraltar). Humanity arrived in Europe at the time when it had the necessary technology to cross maritime barriers, as occurred before the millionth year on the island of Flores (Indonesia),” says Gibert. In this regard, the researcher adds that the Gibraltar route currently requires crossing up to fourteen kilometres of sea route, but “perhaps in the past this distance was shorter at certain times due to the high tectonic activity in this region and fluctuations in sea level favouring migrations.”

“As stated in the paper,” he added, “we have identified other migrations of African fauna through Gibraltar at earlier times, 6.2 million years ago and 5.5 million years ago, when the Strait of Gibraltar was very small.”

The data from this study are very precise thanks to the long sedimentary sequence that emerges in Orce, with 15 vertebrate deposits superimposed in different stratigraphic positions. (Photo: Lluís Gibert)

Human remains in Orce

The human remains found in the Orce sites are a total of five, since the excavations began in 1982 by the paleoanthropologist Josep Gibert. Firstly, two fragments of humerus bitten by hyenas were found in Venta Micena, as well as parts of a cranial fragment consisting of two parietal bones and an occipital bone, associated with remains of an abundant fauna from the early Pleistocene. The human origin of these remains generated great controversy for years, although according to independent paleoproteomic studies carried out by the universities of Granada in Spain and San Francisco in the United States, human proteins were identified in the remains.

The subsequent discovery at nearby sites in Barranco León and Fuente Nueva 3 of two human molar teeth and thousands of Olduvai stone tools—one of the first human stone industries—as well as cut marks on bones “served to consolidate the evidence of the presence of hominids in the early Pleistocene of Orce,” concludes Lluís Gibert.

The study is titled “Magnetostratigraphic dating of earliest hominin sites in Europe.” It has been published in the academic journal Earth-Science Reviews. (Source: Universitat de Barcelona)