Fossil footprints made by a mysterious bipedal creature strolling on a beach in Crete are even older than first suspected. They are about 6.05 million years old, an international team reported in Nature last week.
The paper by Uwe Kirscher et al posits that the footprints, if hominin, have the potential to change the picture of the earliest human evolution, moving it from Africa to the Mediterranean and/or Europe. Others remain unconvinced that the walker wasn’t a bipedal ape and, even if it was hominin, what that might mean.
Even when first found, the strange tracks were originally thought to be incredibly ancient. When first reported in 2017, in the Proceedings of the Geologists’ Association in Science Direct by Gerard Gierlinski et al, the footprints were estimated to have been made 5.7 million years ago. The new estimate throws back the timeline by a little over 300,000 years.
If you wonder why that time difference matters, consider that our species, Homo sapiens, has been around about 300,000 years. Ergo, between the time the tracks were first thought to have been made, and the time they are now thought to have been made, the modern human species could have evolved.
The burning question right now is whether the human species evolved from the creature walking on the Cretan beach 6 million years ago.
There be plantigrade monsters
The tracks (two sets actually) were discovered near the village of Trachilos, western Crete. Who, or what, made them remains controversial. “The trackmaker lacked claws,” the original team wrote, which is categorical. The rest is interpretation based on the totality of the prints’ characteristics.
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The Nature paper concluded the marks were likely made by an early bipedal hominin, not an ape. Among other things, its locomotion was plantigrade – meaning it walked with both toes and metatarsals flat on the ground, as we do.
Cats and dogs, for instance, are not plantigrade. They are digitigrade: they walk on their toes. So the mysterious creature walking in Crete 6.05 million years ago walked like a human. Being plantigrade, however, isn’t enough to determine that they were hominins: baboons are plantigrade, too. So are hedgehogs and bears and rats, and many more.
But the Cretan creature had five toes and other hallmarks of human-type locomotion, and the first team deduced that the tracks were more hominin type than non-hominin primate type.
Even so, the original team cautioned that Crete, which has been geographically isolated in the Mediterranean Sea for millions of years (how many depends who you ask), isn’t within the known stamping ground of the hominin clade and the marks could well have been made by some unknown monkey that convergently evolved human-seeming feet.
The new paper in Nature goes further, suggesting the print-maker could have been Graecopithecus freyberg, a species discovered in 1944 and popularly dubbed “El Graeco.”
Very little fossil evidence has been discovered of this species, which arose shortly after the split between the human and chimpanzee lines roughly around 7 million years ago. (Hominins are the creatures more closely related to humans than to chimps.)
El Graeco was identified based on a jaw and teeth found in Greece. The morphology of the teeth led some to postulate it to be a “probable hominin,” possibly even the first post-chimp ancestor of the Homo line. Some think El Graeco evolved in Europe and Greece, and wandered down to Africa where it evolved into, well, a host of beings and ultimately us.
Others think it was no such thing and was just a late European ape. It also bears adding that not every hominin archaeologists and paleontologists find was ancestral to us; most turned into dead ends on the evolutionary tree. Neanderthals, for instance, are a dead end, even if we retain some of their genes due to interbreeding.
Be all that as it may, the Cretan footprints feature characteristics thought to be unique to hominins – including a forefoot ball, a proper big toe and the fact that the other toes become progressively shorter. The heel is non-bulbous. That smacks of a primitive hominin, and the new paper suggests that “a strong case” has been made for it being phylogenetically ancestral to the footprints found at Laetoli, Tanzania, which are dated to 3.7 million years ago.
The prints left at Laetoli, believed to have been made by australopithecines, featured a longer, more human-like sole, the team writes.
Some even hypothesize based on El Graeco’s teeth and the enigmatic Cretan footprints (if made by El Graeco) that it may be our earliest post-Pan direct ancestor. Furthermore, some hypothesize that its existence in Greece indicates the chimp (Pan) and human lines split in the Mediterranean region, not Africa. There is absolutely no consensus about that.
Primates had existed in Europe around 10 million years ago, but then the environment turned inclement for them. They continued to thrive in Africa.
Prof. Israel Hershkovitz of Tel Aviv University doesn’t find the evidence of a non-African split between chimp and human lineages to be compelling and he also suspects that El Graeco may not have walked bipedally like a human, but got around like a chimp.
Even some australopithecines who lived from about 4 to 2 million years ago had chimp-like shoulders, it turned out in separate research. The conclusion was that Australopithecus, or some australopith species, spent at least part of the time in the trees.
“All we have from Europe is a group of pre-human apes. They are interesting and attest to much more favorable climatic conditions at that time [the late Miocene], but I don’t think they are directly or indirectly associated with human evolution,” said Hershkovitz, who was not connected with this study.
The fact is that the nature and locomotion of very early hominin species remains to be elucidated, let alone whether or not they were ancestral to us. There is an ongoing argument over whether Sahelanthropus tchadensis, a Miocene-era hominin discovered in Chad that also lived between 7 and 6 million years ago (in other words, very roughly around the same time as our creature in Crete), was “habitually bipedal” or preferred to knuckle-walk while on the ground, rearing up mainly in the face of danger or a nice hanging fruit.