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The footprints were discovered by Gerard Gierlinski by chance when he was on vacation on Crete in 2002. Photo: Andrzej Boczarowski

Dozens of fossilized footprints along the coast of Crete could be traces from a bipedal, upright hominid ancestor from 5.7 million years ago, according to a new publication.

The claims, published in the Elsevier journal Proceedings of the Geologists’ Association, would significantly complicate the earliest branches of the human family tree, millions of years before Homo sapiens first rooted down in Africa.

But the claims are also likely to be disputed in the days and weeks to come, concede the authors, primarily from Europe.

“The interpretation of these footprints is potentially controversial,” they write. “The hypothesis that the Trachilos trackmaker was a basal hominin carries substantial implication for early hominin biogeography, as well as for the development of bipedality and the entaxonic (single-big-toed) foot.”

The tracks, which number about 50, are located on the coast at the westernmost part of Crete. The sedimentary layers of limestones, sandstones, and marine fossils at the site place the tracks in the context of 5.7 million years ago, during the Miocene, the anthropologists write.

“What makes this controversial is the age and location of the prints,” said Per Ahlberg of Uppsala University, one of the authors.

It is also the biomechanics apparently preserved in the tracks that stirred the scientists’ interest. The hallux (first digit) was like a disparate big toe of a modern human more than the five similar digits of other primates. Additionally, the ostensible hominid was walking upright, and was also plantigrade (walking firmly on the soles of the feet), the scientists report.

“The tracks are similar in size and have consistent outlines across all the specimens,” they write. “This is an oblique subtriangular shape formed by the combination of a heart-shaped, plantigrade sole with a narrow, tapering heel region, and an asymmetrical digit region with a large hallux and progressively smaller latyeral digits that are all attached to the anterior margin of the sole,” they write.

In context, the upright-walking hominid would be a discovery challenging previous findings. For instance, the 4.4-million-year-old fossils of Ardipithecus ramidus from Ethiopia were reasonably expected to have a more simian foot – and is still believed by most to be a direct ancestor to modern humans.

The new finding would appear to be more in line with the findings of the Graecopithecus in Greece and Bulgaria, as published in May in PLOS ONE. Those fossils from 7 million years ago controversially posited that modern humanity started potentially in Europe, and not Africa.

“Better and more numerous trace fossils are always to be desired, but equally one cannot ignore the currently available evidence and their potential implications, however challenging they may be,” they write. “Further prospecting for ichnofossils and body fossils in the late Miocene of the eastern Mediterranean area has potential to resolve the identity of the Trachilos trackmaker and should be an urgent priority.”

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