Saturday, 2 September 2017

Six Million Year-Old Cretan Footprint Problem - For Creationism!

Trachilos footprint

Credit: Andrzej Boczarowski (CC BY)

Six Million-Year-Old Human Footprint Discovered in Crete Raises Major Questions About Our Evolution

A neat illustration this week of how the popular media distort and misrepresent science in order to appeal to a wider audience and in doing so, feed and reinforce popular misconceptions.

First, we have MSN news announcing that six million year-old human footprints have been found in Crete. This then, of course, is presented as raising 'major questions' about our evolution. Creationists groups on Facebook and elsewhere are already full of claims that this proves science has got everything about evolution all wrong, either neglecting the six million years of explaining them away as proving science even gets the dating wrong.

The source of this story was the press release from Upsala University, Sweden, which announced the publication of a paper by a team based there. Unlike the MSN headline - "Fossil footprints challenge established theories of human evolution" - the headline on this press release was more muted (and of course more accurate). No mention of human footprints there, although there was an attempt to associate the discovery with current understanding of human evolution.

But what understanding was challenged, exactly?

You need to read beyond the headline to get to that.

Newly discovered human-like footprints from Crete may put the established narrative of early human evolution to the test. The footprints are approximately 5.7 million years old and were made at a time when previous research puts our ancestors in Africa – with ape-like feet.

Ever since the discovery of fossils of Australopithecus in South and East Africa during the middle years of the 20th century, the origin of the human lineage has been thought to lie in Africa. More recent fossil discoveries in the same region, including the iconic 3.7 million year old Laetoli footprints from Tanzania which show human-like feet and upright locomotion, have cemented the idea that hominins (early members of the human lineage) not only originated in Africa but remained isolated there for several million years before dispersing to Europe and Asia. The discovery of approximately 5.7 million year old human-like footprints from Crete, published online this week by an international team of researchers, overthrows this simple picture and suggests a more complex reality.

Human feet have a very distinctive shape, different from all other land animals. 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. 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. 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.

The new footprints, from Trachilos in western Crete, 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 prints, but it has the same general form. In short, the shape of the Trachilos prints indicates unambiguously that they belong to an early hominin, somewhat more primitive than the Laetoli trackmaker. They were made on a 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,’ says Professor Per Ahlberg at Uppsala University, last author of the study. [My highlighting]

So not human footprints but human-like footprints. And the question raised is not about human evolution or even the evolution of what might be an early human ancestor, but just where this species lived. It's not even claimed that these footprints were made by the same species as the Laetoli footprints or at the same time.

But it's not till we read the actual paper, published in Proceedings of the Geologists' Association, that we get to the truth. The footprints were actually not really very human-like. Sure, they had a long sole and short toes, but no arch and the hallux or big toe was much further down the sole than in humans. In fact, it looked more like a ape hand with short fingers - pretty much like you would expect an ape hand in the process of evolving into a hominin foot to look like.

So, no re-write of the evolutionary sequence as currently understood needed. The 'mystery' is simply what this 'transitional' species was doing in Crete, and the authors concede that this might be a case of convergent evolution.

Well-preserved footprints. (a–c) The three most well-preserved footprints from surface B2, each shown as a photo (left), laser surface scan (middle) and scan with interpretation (right). a was made by a left foot, b and c by right feet. Scale bars, 5 cm. 1–5 denote digit number; ba, ball imprint; he, heel imprint.*
We describe late Miocene tetrapod footprints (tracks) from the Trachilos locality in western Crete (Greece), which show hominin-like characteristics. They occur in an emergent horizon within an otherwise marginal marine succession of Messinian age (latest Miocene), dated to approximately 5.7 Ma (million years), just prior to the Messinian Salinity Crisis. The tracks indicate that the trackmaker lacked claws, and was bipedal, plantigrade, pentadactyl and strongly entaxonic. The impression of the large and non-divergent first digit (hallux) has a narrow neck and bulbous asymmetrical distal pad. The lateral digit impressions become progressively smaller so that the digital region as a whole is strongly asymmetrical. A large, rounded ball impression is associated with the hallux. Morphometric analysis shows the footprints to have outlines that are distinct from modern non-hominin primates and resemble those of hominins. The interpretation of these footprints is potentially controversial. The print morphology suggests that the trackmaker was a basal member of the clade Hominini, but as Crete is some distance outside the known geographical range of pre-Pleistocene hominins we must also entertain the possibility that they represent a hitherto unknown late Miocene primate that convergently evolved human-like foot anatomy. [My highlighting]*

Given that this date coincides with a perion known as the Messinian Salinity Crisis when the Mediterranean dried up to become a desiccated basin with a few hypersaline lakes, there is not even a mystery how the species that made these tracks came to be on Crete, now an island in the Mediterranean. [Correction: this date preceded the Messinian Salinity Crisis so the mystery remains how the species that made the tracks got to Crete. See comment below.] So what we are left with is the possibility that a relative of a early hominin such as Sahelanthropus had crossed the Sahara during one of the periods when the Sahara was wetter and contiguous with the East African Savannah and had then found its way to Crete, or that an early relative of the hominins had independently evolved bipedalism with a substantial degree of convergence.

These discoveries are interesting and cause us to rethink what we think we already know of the finer details; what they don't do is cause us to revise our general understanding of who we are, how we relate to the other apes and primates or of the evolutionary process which produced us.

Creationists claims to the contrary are amusing wishful thinking which ignores the stark-staringly obvious - that this represents another of those things they refuse to accept - a transitional species. The foot that made those tracks is exactly what a foot sharing the characteristics of both a non-hominin ape and a hominin to look like. The tracks were made by a transitional species.

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  1. Hi Rosa,

    Just found your blog. Interesting piece! However, while the footprints are close to the Messinian salinity crisis in time, they do actually pre-date it - as shown by the fact that the footprint surface is immediately overlain by shallow marine deposits. We have to move about two metres up-sequence before we hit the transition from the shallow marine Vrysses Group to the coarse terrigenous sediments of the Hellenikon Group, which represent the actual drying-out event. So when the footprints were made, the Mediterranean was still full of water.

    All the best, Per Ahlberg (corresponding author)

    1. Thank for that correction. And thank you for taking the time to read my post.


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