Trachilos footprints

The tracks were originally discovered by Gerard D. Gierliński in 2002. During a visit to Trachilos, Gierliński found the tracks, and as he was not planning on staying in Trachilos, Gierliński recorded the footprints to later investigate them in the future. In 2010, he returned to Trachilos with other researchers to explore the tracks in detail.[3]

The tracks were dated by using the underlying rock bed, predominantly sedimentary, and foraminifera,[1] a type of algae that lives on sea floor. The study explains, "The coastal rocks at Trachilos[,] lie within the Platanos Basin, and present a succession of shallow marine late Miocene carbonates and siliciclastics[...] At the top, this marine succession terminates abruptly in the coarse-grained terrigenous sedimentary rocks of the Hellenikon Group[.]"[1] The study continues, stating that the sedimentary rocks would have been created around 5.6 million years ago, at the time of the Messinian salinity crisis (mya).[1] The researchers also found evidence of foraminifera, which were dated at 8.5 mya and 3.5 mya.[1] Given the date of the sedimentary rocks and the foraminifera samples, the researches created an approximate interval of 8.5 mya to 5.6 mya.[1] As the rock sediment containing the tracks resembled that of Hellenikon minerals, the tracks were estimated to be 5.7 mya within the given interval.[1]

The footprints were measured to be 94 mm (millimeters) to 223 mm long and determined to be oriented in a south-west direction.[1] There are clear pressure indexes, resembling that of a modern homo sapien plantigrade structure.[1] The researchers also determined the presence of five digits in the imprints, classifying the track maker as pentadactyl, and lacking claws.[1] As there was no visible evidence of forelimbs from the tracks, the track maker was identified as bipedal.[1] Through 3-D printing and laser scanning, there are impressions found which indicate a ball region, a pulling up motion of the foot, a hallux, and small possible gaps between the first and other digit impressions.[1] Poorly preserved prints lack these gaps however.[1] The lateral digit impressions become progressively smaller so that the digital region as a whole is strongly asymmetrical.[1] The impression of the hallux has a narrow neck and bulbous asymmetrical distal pad, indicating that the tracks were entaxonic.[1] Morphometric analysis showed the footprints to have outlines that are distinct from modern non-hominin primates and resemble those of hominins.[1]

While younger than fossil records of hominins such as Sahelanthropus, found in Chad and dated around seven million years ago, the discovery potentially challenges the generally accepted theory that all early hominins were only present in Africa.[1][2] The print morphology suggests that the trackmaker could be a basal member of the clade Hominini, but as Crete is some distance outside the known geographical range of pre-Pleistocene hominins,[1] researchers say that there is also a possibility that they represent a hitherto unknown late Miocene primate that convergently evolved human-like foot anatomy.[1]

When Gierliński and his team tried to publish the study, they received harsh criticism due to the findings going against the widely accepted hypothesis of early hominins or primates evolving in Africa alone. According to the study, the Trachilos footprints may represent an early hominin or primate species that may have evolved hominin-like feet independently, outside of Africa.[1] This suggests the possibility of convergent evolution.[1] The theory of convergent evolution suggests the possibility of two or more different species adapting similar traits and characteristics to each other, resulting in a similar species.[4] However, the theory is not well supported in this case, as there is no concrete evidence to suggest the theory results in perfect copies of traits or a whole species. As convergent evolution is not scientifically supported, there were doubts if the tracks were footprints at all.[3] This resulted in rejections from many scientific journals when offered to publish the study's findings.

In an interview at the CBC News, researchers claimed that while they were trying to publish their work about the footprints at high-profile publications they got "ferociously aggressive responses", criticism and rejection from reviewers and editors. According to the researchers “Basically, it wasn't a true peer review process at all,” “They were just trying to shut us down.”[3] After multiple rejections from other publications, the study was eventually published in the journal, "Proceedings of the Geologists' Association."[3][1]

Shortly after the research about the footprints was published, eight prints were chiselled out of the rock and stolen.[5] According to Protothema.gr, the culprit was a high school teacher, who was later arrested by Crete authorities at Kasteli, Chania.[5][3] The prints were later found in his house and on a farm.

• Convergent evolution
• Early expansions of hominins out of Africa
• Messinian salinity crisis