Lizard Remnants

Excuse me while I blow away some of this dust.


On Friday, Brian Thomas published an article called Whole Lizard Encased in Amber. What we have is an approximately 23 million year old piece of amber from the state of Chiapas in Mexico which contains preserved within it an entire lizard, albeit quite a small one. Details are scarce, but one news piece claims that it has been “preliminarily identified as a new species of the genus Anolis” – this does not narrow things down particularly well, however, as Anolis already contains nearly 400 living species. Here’s a video which contains some pictures (though the image shown before the video loads is of something else):

The first part of Thomas’ article concerns numerous previous amber finds, claiming that “many clearly identify with recognizable forms” and allowing him to ask why they haven’t evolved in x million years. Those that are different from modern organisms, however, are dismissed as having “apparently gone extinct.” What, then, would he take as evidence of evolution having occurred?

The rest of the article is more interesting, at least to me: it pertains to the old soft tissues issue. Specifically, Thomas says:

Fox News Latino [Thomas’ source article] quoted Francisco Riquelme of the National Autonomous University of Mexico describing the amber specimen as, “a complete and articulated animal that also preserves remains of soft tissue and skin.”

That quote seems to be accurate, or at least is repeated over many sources which will have to do. Thomas summarises his logic neatly:

How can this possibly be true, given that “specimens found in the state date back a minimum of 23 million years ago because that is the age of the amber that is extracted from deposits in the municipalities of Simojovel, Huitihupan, El Bosque, Pueblo Nuevo, Palenque, Totolapa and Malpaso?” After all, lizard tissues are made of proteins, and studies have clearly shown that proteins turn to dust in only thousands of years—especially in tropical temperatures.

This argument rests on two important points. Firstly, there is the claim that proteins can only last “thousands” of years: this seems to be endlessly debated in the literature between the supporters and opponents of Mary Higby Schweitzer’s dinosaur soft tissue finds, with Thomas citing a “comment” paper published in Science in 2008 by the opposition which argues that for her T. rex fossil (buried in hot conditions) the half-life for the collagen that was claimed to have been discovered was much too low (~2000 years) for it to have survived as long as claimed, among other evidence in favour of it being from another source.

The second part is hidden, but I think it is more important here. Thomas says “After all, lizard tissues are made of proteins” – this is true of living lizards certainly, whether ancient or modern, but is it still true of the preserved “remains of soft tissue and skin” trapped in amber? Thomas presumes so, without missing a beat to consider the alternative, but I don’t think this is at all justified.

After doing some digging this afternoon I discovered a paper in the Proceedings of the Royal Society B from 1998, “Chemical preservation of plants and insects in natural resins,” which looks to be quite helpful here. It’s closed access, but I believe a pdf may be available at the NIH website. During the 90’s there was apparently much debate over the possibility that DNA could be (or indeed had been) extracted from organisms trapped within amber. This paper tried to indirectly shed light that question by looking at the preservation of much more resistant biomolecules: lignin in plants and chitin in insects. They asked:

Why do fossils entombed in amber remain in such morphologically pristine condition? And is this morphological perfection matched by the state of preservation of the constituent biomolecules?

Amber is the end result of the the slow hardening of tree resin, via a stage known as “copal.” The types morph into each other without clearly defined boundaries, and so they use the following definitions:

…resins from 250 to 5000 years old are ‘ancient’, and those from 5 ka to 40 ka are ‘sub-fossil’. Older resins are termed ‘amber’.

Their samples consisted of a leaf from 20,000 year old sub-fossil resin, a sample consisting of a related “leaf, sepal and seed from Dominican amber” (which is slightly older than our lizard, given an age of 25-30 million years old in this paper), a bee from 2,000 year old Kenyan resin, and four bees and four beetles from the same Dominican amber. They also had “modern” samples for comparison. For the younger “sub-fossil” leaf they determined that they observed:

…decomposition of the cutin polymer, a symptom of the early stages of plant decay (Tegelaar et al. 1989, 1991). Thus, ligno-cellulose is well preserved in Hymenaea leaves from sub-fossil resin, while the cutin polymer is partly degraded.

Slight degradation, in other words, but overall the leaf was quite well preserved. In contrast, when testing the older material there was no trace of either biomolecules mentioned save for a few decay products. Similar results were found with the insects.

This is all as expected, really, if the amber was as old as claimed. But the temporal distortion produced by young Earth creationism does not seem to so easily fit. The dramatic difference in preservation between the older and younger samples are easily explained if one is at least three orders of magnitude older than the other, but if Dominican amber were produced in the Flood and the Kenyan resin in the period immediately afterwards then the difference between the oldest and youngest cannot be much more than double. Why then the difference?

The result also raises a new question: if there aren’t, in fact, any of the original molecules left making up the fossil then what are they made of? The short answer seems to be just “more resin”:

The most important insight into the mechanism of preservation of the amber inclusions came from investigations of the internal tissues of the insects. Bicyclic resin products (especially those corresponding to molecular weights of 190, 192, 204, 206 and 220 Da) were present in high abundance even in those tissues not directly in contact with the amber. Thus, although the protective coating of amber may prevent collapse of the tissues, the interactions must be more intimate. It is likely that resin molecules formed chemical cross-links involving biochemical components connected via sulphur and/or other terminal olefinic groups of the diterpenoid units. Such molecular interactions explain both the retention of the three-dimensional morphology and the preservation of the finest details of the internal tissues.

Lizard in AmberLet’s return, then, to our lizard: so far as I can tell the piece of amber has not yet been cracked open to examine its internal chemical composiiton, and indeed may never be. Instead, all we know is what we can see through the amber itself. What we see is the “remains of soft tissue and skin,” but that tells us nothing about what, chemically speaking, the tissue is actually made of. Given that the replacement of original tissue by resin is a possibility, if not the most likely situation, you cannot go around claiming that the lizard fossil is made of proteins that should have degraded as if that were the only option. Thomas says:

Like original insect biochemicals and intact body tissues found in amber deposits around the world, these lizard remains retain their pristine quality. If they’re really millions of years old, the body tissues would have certainly turned to dust. Of course, if these ambers originated within the last few thousand years, the age problem dissolves.

The power of amber is that it is capable of preserving 3D fossils in “pristine quality” even after the original material has turned to dust. Also dust, then, is this argument, unless further evidence can one-day revive it.

That leaves Thomas only with his evolutionary stasis argument previously mentioned, but it doesn’t actually apply in this case. Lizards have existed for nearly 200 million years, so finding a fossil that’s only 25 million years old that a creationist could describe as ‘still a lizard’ is unsurprising in and of itself. Instead he has to rely on previous finds, such as a gall mite that we have already looked at in the past, and a gecko leg. The latter is notable because, despite being significantly older than any gecko fossil previously known, it still possesses the distinctive toe pad structures that allow modern geckos to hang on the ceiling. It is, however, only a leg, making it difficult to tell if there are other features that differ from it living relatives, though the size of the toe pads suggest that the adult was probably much larger than modern geckos if nothing else.

Without getting too carried away it’s also true that stasis, at least in terms of that preserved in the appearance of fossils, is not really a problem for evolution either. If a successful group of organisms appears they are well within their rights to hang on for hundreds of millions of years if they can manage it.

In short then, neither of Thomas’ arguments hold water, at least with the evidence available about this particular fossil. Regardless, he is excessively confident about his conclusions, but that is really what we have come to expect.


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