A new study, published in the journal Earth-Science Reviews, helps resolve one of the longest controversies in paleoanthropology: when did early hominins arrive in Europe?
“The chronology of Homo migrations out of Africa has expanded significantly in the past four decades,” said University of Barcelona paleoanthropologist Luis Gibert and his colleagues.
“In 1982, the oldest evidence of Homo in Asia was paleomagnetically dated at 0.9 million years ago in Java, and at 0.7 million years ago in Europe in Italy.”
“Forty years later, the chronology of early Homo beyond Africa was extended to 1.8 million years ago in the southern Caucasus, 1.7-2.1 million years ago in China, and 1.5 to 1.3 million years ago in Java.”
“In Europe, some sites occur in layers with meters of reversed paleomagnetic polarity, indicating they are older than 0.77 million years ago.”
In their research, the authors used magnetostratigraphic dating, a method useing the status of the Earth’s magnetic field at the time the sediment was laid down, to determine the age of five paleontological localities in the Orce region of Spain.
“This technique is a relative dating method based on the study of the inversion of the magnetic poles of the planet due to the internal dynamics of the Earth,” they explained.
“These changes do not have a specific periodicity, but they are recorded in the minerals and make it possible to establish time periods from the different magnetic events.”
“The uniqueness of these sites is that they are stratified and within a very long sedimentary sequence, more than 80 m long,” Dr. Gibert said.
“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.”
Key dated sites showing the world distribution of hominins before 1 million years ago (orange color) and potential dispersion routes. The figure shows sites with Oldowan technology (black dots) older than 2 million years in Africa and older than 1 million years in Eurasia. White dots show the oldest Acheulian sites in Africa (over 1.5 million years old) and in Eurasia (between 1 and 0.8 million years old). The oldest Oldowan and Acheulian tools occur in East Africa at over 2.5 million years ago and over 1.7 million years ago, respectively. In Asia, the oldest Oldowan and Acheulian occur in the Caucasus at 1.8 million years ago (7) and in the Levant corridor at 1.2 million years ago (9) respectively. In Europe the oldest Oldowan and associated hominins occur in Spain (1, 2) with a debated age of 1.6-0.9 million years. Image credit: Gibert et al., doi: 10.1016/j.earscirev.2024.104855.
Their results show that the oldest Orce sites, which lack evidence of hominin activity, are 1.6 million years old and 1.35 million years old.
Three sites higher that contain evidence of early hominins occur at 1.32 million years old (Venta Micena), 1.28 million years old (Barranco León-5), and 1.23 million years old (Fuente Nueva-3).
These chronologies suggest that the Strait of Gibraltar acted as a filter bridge for African species like hominins, Theropithecus oswaldi, and hippos during the Early Pleistocene.
“This new dating would be added to other evidence that would tip the balance in favor of the colonization of Europe through the Strait of Gibraltar, rather than the alternative route: the return to the Mediterranean via Asia,” the scientists said.
“We also defend the hypothesis that they arrived from Gibraltar because no older evidence has been found at any other site along the alternative route.”
“Our results point to a diachronism between the oldest occupation of Asia, measuring 1.8 million years, 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 about 2 million years ago.”
“These differences in human expansion can be explained by the fact that Europe is isolated from Asia and Africa by biogeographical barriers that are difficult to overcome, both to the east (Bosphorus Strait, Dardanelles, Sea of Marmara) and to the west (Strait of Gibraltar),” Dr. Gibert said.
“Humanity arrived in Europe when it had the necessary technology to cross maritime barriers, as happened before a million years ago on the island of Flores, Indonesia.”
“In this sense, the Gibraltar route currently requires crossing up to 14 km 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 the fluctuations in sea level that favored migrations.”
“We identified other migrations of African fauna through Gibraltar at earlier times, 6.2 and 5.5 million years ago when the Strait of Gibraltar was very narrow.”
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Luis Gibert et al. Magnetostratigraphic dating of earliest hominin sites in Europe. Earth-Science Reviews, published online July 2, 2024; doi: 10.1016/j.earscirev.2024.104855