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Friday, August 29, 2014

Oh Dem Young Bones

Posted by jlwile on May 16, 2011

An osteocyte-like structure found in a supposedly 70-million-year-old fossil (Click for credit)

In three previous articles (here, here, and here), I discussed bones that are supposed to be millions of years old and yet have soft tissue and large organic molecules in them. This is quite hard to understand if the fossils truly are that old, since soft tissue and large organic molecules are expected to decay fairly rapidly, even under ideal conditions. For example, an interdisciplinary approach to understanding how large organic molecules such as protein and DNA could be preserved over time suggested that even if a fossil were kept at the freezing point of water, collagen (a protein found in bone) should decay away so that it becomes undetectable in just under three million years.1 Nevertheless, collagen has been found in fossils that are supposed to be more than twenty times that old!


Of course, if you are desperate to believe in an ancient earth and are therefore forced to think such fossils are really that old, you could hope that either very special conditions existed for the fossils in which the soft tissue and proteins were found, or you could hope that the soft tissue and proteins were the result of some kind of contamination. A recent paper in PLoS ONE has, in my opinion, laid both of those hopes to rest.

The paper examines samples from a mosasaur fossil that is 70 million years old, according to scientifically-irresponsible dating techniques. A microscopic analysis of this fossil showed all sorts of amazing things. For example, when the bone was etched with acid and then examined with a microscope, several structures that look like mature bone cells (called osteocytes) were found. In addition, all sorts of fibrous tissue was found, and amazingly enough, that fibrous tissue absorbed dye just like connective tissue from a modern bone!2

But what was the fibrous tissue made of? The authors show beyond all reasonable doubt that it contained collagen, which is a complex protein found in all bones. In my mind, their detailed analysis is part of what makes this paper so important.

As I stated before, some who are desperate to believe that fossils like this mosasaur fossil really are tens of millions of years old want to believe that any soft tissue or proteins recovered from them don’t really belong to the fossil itself. Instead, they are the result of recent bacterial contamination or some other process that would yield fibrous organic tissue. However, the authors show that this is just not possible.

For example, they used infrared light to probe the fibrous tissue that they isolated from the fossil, but instead of using a standard source for this infrared light, they used a particle accelerator known as a synchrotron. This produces incredibly high-intensity infrared light, which can provide significant details on the molecules in the tissue. They compared the results they obtained with tissue from their fossil to those obtained with bacterial cells and bacterial biofilms, and they show quite conclusively that the fibrous tissue in the fossil could not possibly be the result of bacterial contamination. They also compare their results to a sample of pure collagen and to the fibrous tissue from a modern monitor lizard. The results are completely consistent, indicating that the fibrous tissue from the fossil is not only reptile tissue, but it is reptile tissue that contains a lot of collagen.

They did several other tests on the tissue recovered from the fossil to conclusively demonstrate that they had recovered collagen from it. For example, they exposed it to antibodies that are designed to bind with collagen, and the antibodies did, indeed, bind to molecules in the fibrous tissue. This is important, because if the collagen in the fossil had decayed significantly, the antibodies would not bind well to it. They also examined the amino acids that were in the fibrous tissue, and the distribution was exactly what you would expect for collagen and other structural proteins. In the end, they make the strong case that the collagen they found really was from the original mosasaur that formed the fossil and that said collagen retained much of its original chemical structure.

These results, while impressive enough, are not the only important results that come from this paper. In fact, this paper tells us something about what to expect from the fossil record in general. As the authors note:

Thus, the preservation of primary soft tissues and biomolecules is not limited to large-sized bones buried in fluvial sandstone environments, but also occurs in relatively small-sized skeletal elements deposited in marine sediments.

This makes their results all the more important. It is one thing to have soft tissue and proteins preserved in a large bone that was buried in fluvial sandstone. After all, the large bone might protect the fragile tissue, and fluvial sandstones are supposed to have been deposited by rivers. Thus, it is likely that the sediments which formed the sandstone weren’t inundated with water for a long time. So even though finding soft tissue and proteins in a large bone that was encased in fluvial sandstone for millions of years is surprising, you might be able to imagine that the environment offered some special conditions that helped to prevent the expected decay.

However, these results come from a small bone, and the bone was found in sediments that should have been soaked in water for a long time. This makes it extremely hard to believe that the fossil had any special conditions that would help keep soft tissue and proteins from decaying away relatively quickly.

Of course, if one takes the more reasonable approach and is willing to consider that the fossil isn’t anywhere close to 70 million years old, the results of this incredible study are a lot easier to understand.

REFERENCES

1. Nielson-Marsh, Christina, “Biomolecules in fossil remains: Multidisciplinary approach to endurance,” The Biochemist, 12-14, June 2002
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2. Johan Lindgren, et. al., “Microspectroscopic Evidence of Cretaceous Bone Proteins,” The Biochemist, PLoS ONE, 2011
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Comments

9 Responses to “Oh Dem Young Bones”
  1. J. S. says:

    To me, the most remarkable aspect of the study is that they found enough C-14 to date, and that the calculated date was 24,600 years BP. Although the researchers attributed the C-14 to post-burial bacterial activity, they did not find any bacterial proteins or hopanoids that might have contributed the carbon. The most straightforward conclusion is that the C-14 is original to the soft tissue.

    I hope there will be more studies of this kind to match the increasing pace of soft tissue discovery. It also would appear that if you want soft tissue, mosasaurs are the fossils of choice–this is the third mosasaur that I know of in which soft tissues have been found.

  2. jlwile says:

    I am not as impressed by the C-14 data, J.S., because I do think that can be easily chalked up to contamination. I agree with you that it probably is original C-14, but there is just no way to confirm that. The collagen has been clearly confirmed as belonging to the mosasaur, however, so that’s what is most impressive to me.

    You are right. More studies like this need to be done. As was made clear in a study of a fossil salamander, “high-fidelity organic preservation of extremely labile tissues is not only feasible, but likely to be common.”

  3. J. S. says:

    The problem with ascribing the C-14 to contamination when there is no inherent reason to do so is that it casts doubt on all other C-14 dates. If it is valid to claim that the C-14 in the mosasaur is not original to the tissue because it conflicts with an externally derived age for the fossil, then all objectivity has been removed from the dating method. And if, as the researchers suggest, the presence of bacterial DNA is sufficient to support the presumption of contamination, then every C-14 dated material should be screened for bacterial DNA as well and presumed contaminated if it is found. It’s a question of applying a consistent methodology in all cases.

  4. jlwile says:

    J. S., the authors do give some evidence for contamination. They say that they found one bacterial DNA sequence and that that there were microscopic clusters of bone-boring cyanobacteria found. In addition, they found two short DNA sequences of possible hare/rabbit origin that indicates the outer surface of the bone might have been painted with animal glue at some point.

    Thus, while I agree that you cannot dismiss the C-14 as contamination without evidence, I think they provide enough evidence to at least make one skeptical that the C-14 came from the mosasaur.

  5. J. S. says:

    Thanks for clarifying the point–that makes sense.

  6. Dan says:

    Dr. Jay, is it possible the same kind of contamination occurred with the samples analyzed in the RATE study on C-14 in coal and diamond? Or do you think the conclusions from their study are pretty solid?

  7. jlwile says:

    Diamonds are a lot different from fossils. It is very, very hard for them to be contaminated, especially when the proper preparation procedures are followed. In the RATE study, the proper preparation procedures were followed, so I seriously doubt there is a contamination issue there. Also, there were twelve separate diamonds from four different countries. Thus, I think those results are fairly strong.

    The coal is a different matter entirely. I think it is very difficult to get rid of contamination in coal, and worse yet, it is hard to spot the possibility of contamination. Thus, I don’t think those results are as convincing. I do have to say, however, when combined with the large number of examples from the literature, the results do become more compelling.

  8. J.S. says:

    Dr. Wile, do you know if scientists are generally as scrupulous in searching for and mentioning possible sources of external contamination as they were in this case?

  9. jlwile says:

    In general, those who deal with radiometric dating are quite scrupulous when it comes to external contamination, especially when the technique they employed in this study (accelerator mass spectrometry) is used. It is very sensitive, so contamination is a huge issue. I did my thesis studies at the University of Rochester Nuclear Structure Research Lab, which at that time had a very active group doing accelerator mass spectrometry. I observed them quite a bit, and they were scrupulous. Of course, if the method is built on false assumptions, the level of scrupulousness doesn’t make it any more reliable.

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