From time to time, new fossil finds make the history of human evolution need to be rewritten. Once again, a discovery has puzzled scientists, and has put to the test what was believed about the origin of the first humans. These are Homo sapiens footprints discovered in Crete , and they are approximately 5.7 million years old. A moment in which, until now, our ancestors were located in Africa, and with the feet more similar to those of a monkey.
Until now, the first humans were located in Africa 3.7 million years ago. A conclusion that we have reached thanks to the discovery of Australopithecus fossils in South and East Africa.
The recent history of human evolution may have to be rewritten, or the iconic 3.7 million-year-old Laetoli footprints from Tanzania.
But the new discovery, published in the journal Proceedings of the Geologists’ Association , shows human feet and vertical locomotion , cementing the idea that hominids (early members of the human lineage) not only originated in Africa but remained isolated there for several millions of years before dispersing to Europe and Asia.
Human feet have a very distinctive shape, different from all other land animals. The combination of a long soles of the feet, five short toes forward without claws, and a hallux (thumb) larger than the other toes is unique. The feet of our closest relatives, the great apes, look more like a human hand with a thumb-like hallux sticking out to one side.
The Laetoli footprints, thought to have been made by Australopithecus , are similar to those of modern humans , except that the heel is narrower and lacks a proper arch. By contrast, the 4.4-million-year-old Ardipithecus ramidus, the oldest known hominin from complete fossils, has a simian foot. The researchers 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.
But the new tracks, from Trachilos in western Crete, are unmistakably human in shape , and are older. This is especially detected thanks to the toes. The big toe is similar to our own in shape, size, and position. The sole of the foot is proportionally shorter than in the Laetoli prints, but has the same shape. In short, the shape of the Trajilos footprints unequivocally indicates that they belong to a primitive hominimus , somewhat more primitive than the latirista Laetoli. They were made on a sandy shoreline, possibly a small river delta, while the Laetoli tracks were made in volcanic ash.
A controversial finding
“What makes this finding controversial is the age and location of the footprints,” in the words of Professor Per Ahlberg of Uppsala University, author of the study.
The prints, at around 5.7 million years old, are younger than the oldest known fossil hominin , Sahelanthropus from Chad , but more than a million years older than Ardipithecus ramidus with its ape-like feet. This is in conflict with the hypothesis that Ardipithecus is a direct ancestor of later hominins.
Furthermore, so far, all hominid fossils older than 1.8 million years (the age of the first Homo fossils from Georgia) came from Africa , leading most researchers to conclude that this was where the group was evolving. However, the Trachilos footprints are firmly dated, using a combination of foraminifera (marine microfossils) from the underlying beds, plus the fact that they lie just below a very distinctive sedimentary rock formed when the Mediterranean Sea briefly dried up 5 years ago. , 6 million years.
During the time when the Trachilos footprints were made, a period known as the late Miocene, the Sahara Desert did not exist; savanna-like environments extend from North Africa to around the eastern Mediterranean. Furthermore, Crete had not yet separated from the Greek mainland . Thus, it allows us to see how the first hominids could have lived between south-eastern Europe and Africa , and left their footprints on a shore of the Mediterranean that would one day be part of the island of Crete.
“This discovery challenges the established narrative of early human evolution head-on and is likely to generate much debate. It remains to be seen whether the human origins research community will accept fossil footprints as conclusive evidence for the presence of hominins in Miocene Crete. “says Per Ahlberg.
References and image:
Grzegorz Niedźwiedzkib, Martin G. Lockleyc, d, Athanassios Athanassioue, Charalampos Fassoulasf, Zofia Dubickag, Andrzej Boczarowskic, Matthew R. Bennettk, Per Erik Ahlbergb, Gerard D. Gierlińskia. Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete? (2017). Proceedings of the Geologists’ Association. Doi.org/10.1016/j.pgeola.2017.07.006
