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Soft Tissue in Mollusk Fossils and the Case for a Young Earth

When it comes to science-faith discussions, the age of the earth is one of the most contentious topics among evangelicals and conservative Christians. Most of the scientific debate surrounding this issue centers on astronomy and geology, but young-earth creationists have recently turned to biology to make their case for a young Earth. One prominent argument relies on the unexpected recovery of soft-tissue remains from a variety of fossils that date from a few million to several hundred million years in age.

Young-earth creationists argue that it is impossible for fossils to contain soft-tissue remnants and be millions of years old. Soft tissues shouldn’t survive that long; they should readily degrade in a few thousand years. In the young-earth view, the soft-tissue finds challenge the reliability of radiometric dating methods used to determine the fossils’ ages and, consequently, Earth’s antiquity. They assert these breakthrough discoveries provide compelling scientific evidence for a young earth and support the idea that the fossil record results from a recent global (worldwide) flood. (Go here for an excellent review article that details this argument.)

Protein Films

Recovery of intact protein films from fossilized gastropod shells seemingly adds to the case for a young Earth.1 Researchers from the Carnegie Institution in Washington, DC, were able to release thin protein sheets from reddish-brown fossilized Ecphora shells. The researchers treated the shells with dilute acid and this treatment dissolved the mineral component (calcium carbonate) of the shell, leaving behind a flexible film. The researchers learned the film is composed of intact proteins and has an amino acidcomposition matching that of modern shell-binding proteins of mollusks.2 The fossil shells were recovered from Calvert Cliffs, a formation in Maryland that spans between 8 and 18 million years in age. The researchers estimate the age of the specimens they analyzed at around 15 million years in age.

How could intact protein films survive for 15 million years? Nearly every scientist would agree that soft tissue readily degrades. If soft tissue somehow survives, it should be a rare occurrence. In this respect, young-earth creationists are raising good questions about soft tissue associated with fossils and the age of the earth. Could it be that there really is something wrong with radiometric dating methods? Does the discovery of a 15-million-year-old protein film (and other fossilized soft tissues) represent genuine scientific evidence for Earth being only a few thousand years old?

Not really. Despite many young-earth creationists’ claims, there is no good reason to think that radiometric dating methods are unreliable. If these methods are sound, then the soft-tissue remnants associated with fossils must be millions of years old. But how can that be?

Soft-Tissue Breakdown

To address this question it is important to understand why soft tissue degrades. Its breakdown results from exposure to oxygen, water, relatively high temperatures, microbial activity, and the activity of enzymes found in the environment (such as proteases, in the case of shell-binding proteins.) If an organism’s remains are “buried” in a relatively cold environment that excludes oxygen and water, and if there are materials in the surroundings that inhibit the growth of microbes and deactivate enzymes, the soft tissue will persist.

There might be other mechanisms at work that can actively preserve soft tissue. For example, minerals associated with soft tissue protect it from degradation. It’s also important to recognize that some molecules are more structurally robust than others and, therefore, are more likely to endure the fossilization process. Applying these insights helps explain why the shell-binding protein film persisted for 15 million years.

Even before they conducted their work, the Carnegie researchers suspected that soft-tissue remnants were associated with the fossilized Ecphora shells because of their reddish-brown color. They reasoned that this color must come from pigments. Mollusks will incorporate pigments (such as carotenoids), consumed as part of their diet, into their shells. These pigments are light sensitive and will readily breakdown after death. The Ecphora fossils’ bright coloring indicated to the investigators that the shell matrix must protect the pigments and led them to hypothesize that other soft-tissue remnants might be associated with the shells as well.

All the other fossilized mollusk shells found at the Calvert Cliffs site are chalky white, indicating that the pigments originally associated with those shells were destroyed over time. The researchers note that the calcium carbonate of the Ecphora shell exists as calcite. The calcium carbonate of other fossilized mollusk shells is formed from aragonite. The researchers speculated that interactions between calcite and the shell-binding protein film protected the organic material from degradation and helped preserve pigments in the shells.

Still, these protein films have experienced some degradation. During their analysis of the protein sheets, the Carnegie team identified a number of chemical compounds that are likely breakdown products of proteins and polysaccharides. The existence of these breakdown products is consistent with the protein film’s 15-million-year age.

Though unexpected, the recovery of soft tissue from 15-million-year-old shell fossils is explainable. This is also true for collageneumelaninquinones, and chitin associated with fossils. The presence of soft tissues in fossils doesn’t undermine the reliability of radiometric dating and other measurements of Earth’s and life’s antiquity. In short, soft tissues associated with fossils can’t be used to support the young-earth paradigm.

  1. J. R. Nance et al., “Preserved Macroscopic Polymeric Sheets of Shell-Binding Protein in the Middle Miocene (8 to 18 Ma) Gastropod Ecphora,” Geochemical Perspective Letters 1 (January 20, 2015): 1–9.
  2. The architecture of mollusk shells consists of alternating organic and inorganic layers. The organic layer is made up of sheets of shell-binding proteins and polysaccharides. The organic layer promotes the deposition of minerals made up of calcium carbonate, such as calcite and aragonite.