5.6-Million-Year-Old Hominin-Like Footprints in Crete Challenge Theories of Human Evolution | Paleoanthropology

Researchers have found late Miocene footprints — which show hominin-like characteristics — near the village of Trachilos, west of Kissamos, in the Chania Prefecture of Crete, Greece. The footprints, described in a 31 August study in the Proceedings of the Geologists’ Association, may put the established narrative of early human evolution to the test.

The Trachilos footprints were discovered by Dr. Gerard Gierlinski, a paleontologist at the Polish Geological Institute, by chance when he was on holiday on Crete in 2002. Dr. Gierlinski identified the footprints as those of a mammal. In 2010, he returned to the site together with Dr. Grzegorz Niedzwiedzki, a Polish paleontologist at Uppsala University, to study the footprints in detail. Together they came to the conclusion that the footprints were made by hominins. Image credit: Andrzej Boczarowski.

The Trachilos footprints were discovered by Dr. Gerard Gierlinski, a paleontologist at the Polish Geological Institute, by chance when he was on holiday on Crete in 2002. Dr. Gierlinski identified the footprints as those of a mammal. In 2010, he returned to the site together with Dr. Grzegorz Niedzwiedzki, a Polish paleontologist at Uppsala University, to study the footprints in detail. Together they came to the conclusion that the footprints were made by hominins. Image credit: Andrzej Boczarowski.

Ever since the discovery of Australopithecus in South and East Africa in the 1920s-90s, the origin of the human lineage has been thought to lie in Africa.

More recent discoveries in the same region, including the 3.75-million-year-old Laetoli footprints from Tanzania, have cemented the idea that hominins not only originated in Africa, but remained isolated there for several million years before dispersing to Europe and Asia.

The discovery of the Trachilos footprints, which are at least 5.6 million years old and thus approximately 2 million years older than the hominin trackways from Laetoli, suggests a more complex reality.

“Human feet have a very distinctive shape, different from all other land animals,” the study authors explained.

“The combination of a long sole, five short forward-pointing toes without claws, and a hallux (‘big toe’) that is larger than the other toes, is unique.”

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“The feet of our closest relatives, the great apes, look more like a human hand with a thumb-like hallux that sticks out to the side.”

“The Laetoli footprints, thought to have been made by Australopithecus, are quite similar to those of modern humans except that the heel is narrower and the sole lacks a proper arch. By contrast, the 4.4-million-year-old Ardipithecus ramidus from Ethiopia, the oldest hominin known from reasonably complete fossils, has an ape-like foot.”

“Paleoanthropologists who described Ardipithecus argued that it is a direct ancestor of later hominins, implying that a human-like foot had not yet evolved at that time.”

Photograph of two prints possibly representing a static stance of one individual. Image credit: Gierlinski et al, doi: 10.1016/j.pgeola.2017.07.006.

Photograph of two prints possibly representing a static stance of one individual. Image credit: Gierlinski et al, doi: 10.1016/j.pgeola.2017.07.006.

The Trachilos footprints have an unmistakably human-like form. This is especially true of the toes. The big toe is similar to our own in shape, size and position; it is also associated with a distinct ‘ball’ on the sole, which is never present in apes.

The sole of the foot is proportionately shorter than in the Laetoli footprints, but it has the same general form.

In short, the shape of the Trachilos footprints indicates unambiguously that they belong to an early hominin, somewhat more primitive than the Laetoli trackmaker. They were made on sandy seashore, possibly a small river delta, whereas the Laetoli tracks were made in volcanic ash.

“What makes this controversial is the age and location of the prints,” said senior author Professor Per Erik Ahlberg, of Uppsala University.

“The Trachilos footprints are younger than the oldest known fossil hominin, Sahelanthropus from Chad, and contemporary with Orrorin from Kenya, but more than a million years older than Ardipithecus ramidus with its ape-like feet.”

“This conflicts with the hypothesis that Ardipithecus is a direct ancestor of later hominins.”

“Furthermore, until this year, all fossil hominins older than 1.8 million years (the age of early Homo fossils from Georgia) came from Africa, leading most researchers to conclude that this was where the group evolved,” the researchers said.

“However, the Trachilos footprints are securely dated using a combination of foraminifera from over- and underlying beds, plus the fact that they lie just below a very distinctive sedimentary rock formed when the Mediterranean sea briefly dried out, 5.6 million years ago.”

Earlier this year, another team reinterpreted the fragmentary 7.2 million year old primate Graecopithecus freybergi from Greece and Bulgaria as a hominin.

“During the time when the Trachilos footprints were made, the Sahara Desert did not exist; savannah-like environments extended from North Africa up around the eastern Mediterranean. Furthermore, Crete had not yet detached from the Greek mainland,” the scientists said.

“It is thus not difficult to see how early hominins could have ranged across south-east Europe and well as Africa, and left their footprints on a Mediterranean shore that would one day form part of the island of Crete.”

“This discovery challenges the established narrative of early human evolution head-on and is likely to generate a lot of debate,” Professor Ahlberg said.

“Whether the human origins research community will accept fossil footprints as conclusive evidence of the presence of hominins in the Miocene of Crete remains to be seen.”

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Gerard D. Gierliński et al. Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete? Proceedings of the Geologists’ Association, published online August 31, 2017; doi: 10.1016/j.pgeola.2017.07.006

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