A groundbreaking investigation, detailed in the esteemed journal Earth-Science Reviews, offers resolution to a protracted debate within paleoanthropology concerning the initial ingress of early hominins into Europe.
Archaic hominins. Image credit: Ninara / CC BY 2.0.
“The temporal framework for Homo dispersals originating from Africa has undergone considerable expansion over the past four decades,” remarked Luis Gibert, a paleoanthropologist from the University of Barcelona, alongside his research associates.
In 1982, the most ancient indicators of Homo presence in Asia were dated via paleomagnetism to 0.9 million years ago in Java, with European evidence from Italy dating back to 0.7 million years ago.
Forty years onward, the timeline for early Homo outside Africa has been pushed back 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 the island of Java.
In Europe, certain fossiliferous horizons are situated within sedimentary layers exhibiting reversed paleomagnetic polarity, implying an age exceeding 0.77 million years.
Through their meticulous research, the investigators employed magnetostratigraphic dating—a methodology that leverages the Earth’s magnetic field orientation during sediment deposition—to ascertain the age of five paleontological sites in Spain’s Orce region.
“This analytical technique, a form of relative dating, is predicated on the examination of planetary pole inversions driven by Earth’s internal geological processes,” they elaborated.
“While these magnetic field shifts lack a fixed cyclical pattern, they are imprinted within geological strata, thereby enabling the delineation of temporal intervals through distinct magnetic events.”
“A distinguishing characteristic of these sites is their stratified nature, embedded within an exceptionally extensive sedimentary sequence exceeding 80 meters in thickness,” stated Dr. Gibert.
“Typically, discoveries of this kind are confined to cave systems or occur within truncated stratigraphic columns, precluding the development of lengthy paleomagnetic records necessary for identifying multiple magnetic reversals.”
Theropithecus oswaldi and hippos, during the Early Pleistocene epoch.
“This updated dating, in conjunction with other accumulated evidence, strongly supports the hypothesis of Europe’s colonization via the Strait of Gibraltar, rather than through an alternative pathway involving a return to the Mediterranean basin by way of Asia,” the researchers stated.
“Furthermore, we advocate for the Gibraltar route hypothesis, as no earlier evidence has been discovered at any other location along the purported alternative migration path.”
“Our findings reveal a temporal disparity between the earliest established occupation in Asia, dated at 1.8 million years ago, and the most ancient hominin presence in Europe, estimated at 1.3 million years ago. This implies that African hominids reached southwestern Europe more than 0.5 million years after their initial departure from Africa, which occurred approximately 2 million years ago.”
“Variations in the pace of human expansion can be attributed to the geographical isolation of Europe from Asia and Africa by formidable biogeographical barriers, both to the east (encompassing the Bosphorus and Dardanelles straits, and the Sea of Marmara) and to the west (the Strait of Gibraltar),” Dr. Gibert explained.
“The migration into Europe likely occurred when early humans possessed the requisite technological capabilities to traverse marine expanses, analogous to migrations observed earlier on the island of Flores in Indonesia, prior to one million years ago.”
“In this context, while the modern Strait of Gibraltar necessitates crossing approximately 14 kilometers of open water, it is plausible that past distances were substantially reduced during periods of heightened tectonic activity in the region and fluctuating sea levels, which would have facilitated migratory movements.”
“We have identified other instances of African fauna migrating through Gibraltar at even earlier epochs, specifically 6.2 and 5.5 million years ago, when the Strait of Gibraltar was considerably narrower.”
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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
