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Primitive or Rotten?

By Andrew V. Ste. Marie

What does studying rotten fish have to do with paleontology? Surprising as it may seem, results of a recent study on the decay of fish carcasses may shed much light on some evolutionary claims. Three scientists from the University of Leicester in the United Kingdom published their research recently in the scientific journal Nature. They were investigating how decay might affect identification in the cases of some supposedly primitive fish-like fossils, such as Cathaymyrus, Metaspriggina, Pikaia, and the Canadian and Chinese yunnanozoans. It has been generally assumed by evolutionists that the decay that may have affected the fossilized animals was random – that is, there was no particular pattern of decay that would have affected identification. Allegedly primitive and advanced characters, or those that are “informative” or “uninformative” for identification would rot away pretty much randomly and not affect identification. Is this a valid assumption? The three University of Leicester scientists put it to the test. The scientists watched the decay of representatives of two types of fish-like creatures, both of which were supposedly advanced or “crown” members of their groups. They collected samples of juvenile lampreys (Lampetra fluviatilis), which are vertebrates of the petromyzontid group, from the River Ure in North Yorkshire, United Kingdom. They also used specimens of Branchiostoma, a fish-like chordate, a group supposedly closely related to vertebrates. These specimens were collected from the coastal waters of Argelès-sur-Mer, France. All of the specimens were killed by a poison overdose, using a chemical which would not adversely affect the decay bacteria. The dead fish were then placed in clear containers filled with water – artificial sea water for Branchiostoma, and filtered, deionised water for the lampreys. The containers were sealed shut and the decay was monitored. The researchers “destructively sampled three individuals of each species at intervals that were varied to capture rapid early decay and later, slower stages” (reference #1). The results of this research were fascinating. The researchers found that as the supposedly “crown” chordate and “crown” vertebrates decayed, they lost their so-called advanced features first, and the “uninformative” features, which these animals supposedly evolved first, were very decay-resistant. This made the carcasses look more and more primitive as they decayed, and the “crown” vertebrate and “crown” chordate decayed until they both looked like “stem chordates.” This means that if the greatly decayed lamprey was fossilized and later discovered, it would be identified by evolutionists as a primitive chordate, when in reality it was what was left after a “crown” petromyzontid (juvenile) had rotted. An article in the same issue of the journal Nature, discussing the results of the study, summarized it well: “Decomposition and the loss of morphological features have the effect of making a fossil seem less evolved than the organism was in life, and therefore closer to an ancestral (stem) position on an evolutionary tree” (#2 in our reference list). The authors of the original study show that the rotten fish they studied really did look similar to some of the supposedly primitive fossil fish-like animals: “The fossil Cathaymyrus…[is thought to be] a stem chordate. However, when viewed in light of the decay bias we have identified, Cathaymyrus is comparable to Branchiostoma at an advanced state of decay…” (emphasis added, from #1 on our reference list). The implications of this are important. The supposed primitive ancestors of vertebrates, including taxa such as Cathaymyrus, Metaspriggina, Pikaia, and the Canadian and Chinese yunnanozoans, may simply be the decayed remnants of more “advanced” looking creatures. Because of this possibility, these fossils cannot be identified confidently, and no evolutionary claims can be made from them. In the meantime, we can have full confidence about the true origin of the first vertebrates, among which were sea dragons, fish, and birds: “And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good” (Genesis 1:20-21).

Thanks to paleontologist Joe Taylor for bringing this research to my attention.


1. “Non-random decay of chordate characters causes bias in fossil interpretation,” by Robert S. Sansom, Sarah E. Gabbot, & Mark A. Purnell, Nature 463:797-800

2. “Decay distorts ancestry,” by Derek E. G. Briggs, Nature 463:741-743

3. “Rotten Paleontology,” by Ian Juby, Creation/Evolution News, February 25, 2010, (Accessed February 24, 2010)

4. “Novel studies of decomposition shed new light on our earliest fossil ancestry (w/ Video),” (Accessed February 24, 2010)


Originally published in The Witness March 2010.