Friday, September 1, 2017

About those Trachilos tracks

I suppose I should say something about the Trachilos tracks. I've received a couple messages about this on Twitter and Facebook. Scientists from a mostly European collaboration announced today that they have discovered early hominin trackways from northwest Crete. They date the tracks to around 5.7 million years ago (late Miocene). Unsurprisingly, headlines claim that this is a "huge" "game-changer" and "challenges theories of human evolution." Let's see what the hype is about.

First of all, these are some smudgy footprints. Here are some clear ones that the authors included in their paper to support their anatomical inferences.

Select Trachilos prints from Gierliński
et al. Figure 9.

Note the 5 cm scale bars. Prints A and B are about 10 cm long, and C is about 12-15 cm. That's four to six inches for us Americans. By contrast, my foot is about a foot long. The smudginess of individual prints does nothing to detract from the bipedal appearance of the tracks though. Check out this shot:

Stance indicated by Trachilos tracks. From
Gierliński et al. Figure 8.

Note again that scale marker. Those prints are about 15 cm apart, which is about 6 inches. Whatever made these prints was quite small.

What can we make of these? Are they hominin prints? Could be. The prints give me the impression of a foot that is slipping around on mud as the creature walks, so I'm not sure I want to put a lot of stock in the purported anatomical details of the prints. Nevertheless, I also don't want to underestimate the validity of the trackways as a whole. They are very interesting and suggestive of hominin tracks.

Are they game changers? Not really. The conventional date for these prints is 5.7 million years. On the evolutionary scale, that's just about the time of the human/chimpanzee last common ancestor. There are putative fossil hominins from Africa that are older than these tracks (Sahelanthropus) and one (Orrorin) that may have been a contemporary. So if these tracks were made by a bipedal hominin, then they are in good company with other African fossils that are also purported to be early hominins. The only thing mildly interesting about the implications is that they extend the range of early hominins out of Africa. Not much of a shocking result. In any event, hominin fossils from that putative age are pretty scant, and this adds just a bit more evidence.

What might this mean for creationists? If the tracks do turn out to be hominins in Europe, it's not a threat to evolution. It just means that early hominins were more widely dispersed than evolutionists previously thought. Big deal.

A creationist might interpret these as either very small early humans (not outside the realm of possibility given the existence of other small-bodied humans like 9-year-olds or Homo floresiensis) or as early representatives of the created kind that includes other bipeds like Lucy (Australopithecus afarensis). I don't think it matters very much, but it would be nice to see a set of bipedal animal tracks from a non-human created kind in closer proximity to Ararat than African australopiths.

So long story short: These footprints are conventionally older than most African human and bipedal ape fossils. They might have been made by really small people or by small bipedal apes. Either way, they're neat. They do not represent a huge threat to theories of human evolution, since they are consistent with other hominin fossils known from Africa. They're merely found in a location we hadn't known about before. I suspect any controversy over the prints will be over the quality of the prints rather than the fanciful notion that they are a threat to human evolutionary theories.

Don't like my comments? Read the article for yourself:

Gierliński et al. 2017. Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete? Proceedings of the Geologists' Association DOI: 10.1016/j.pgeola.2017.07.006.

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