Re: Schwei[tz]er and Soft Tissue Recovery

[David Marjanovic <david.marjanovic@gmx.at>]

>  At the SVP meeting, there was an interesting investigation on the
>  metagenomics of dinosaur soft tissue preservation. The gist of it
>  was that the material recovered from Mesozoic fossil bone had gene &
>  protein material that matched WAY too many living things, and
>  matched them WAY too perfectly.

Wait. What? There's DNA in it??? That _has_ to be contamination. Protein 
is one thing, iron-crosslinked protein yet another, but DNA, even in 
tiny fragments, doesn't last longer than 100,000 years -- unless it's 
frozen, which it's not, or maybe unless it stays completely dry 
throughout, which isn't possible in a well-drained sandstone. Did they 
really say there's DNA in it? I didn't notice that on their poster.

>  One thing to be 'turkey-like' (and therefore distantly related to
>  birds), another to be a plain old turkey. The authors at the talk
>  supposed that genetic and protein material had leached through the
>  soils, and invaded the fossil bones (Researchers in the tropics, as
>  far as I understand it, do (somewhat similar) environmental DNA
>  sampling to ID the different genetic types of things that are out in
>  the forest (w/o having to ID the living animal). That's a pretty
>  fascinating discovery in and of itself. They also felt that bacteria
>  could make (and indeed showed similar) tubular structures that look
>  like blood vessels.
>
>  Later I noticed a poster from (if I recall correctly) someone in Dr.
>  Schweitzer's group identifying the material in the soft tissue as
>  definitely collagen.

...without sulfur in it. They proposed, on the poster, that it could 
have been lost by an unknown diagenetic process. :-/

The material they sequenced may all have been contamination. Yes, even 
the one identical to ostrich collagen; contamination in a lab is easy, 
and the methods are sensitive enough to detect tiny amounts.

>  So what does anyone think about this, seems like the issue is still
>  open, and this material was recovered quite a while ago.
>
>  Has there been any sectioning of the 'goop' that Dr. Schweizter
>  found, for histological examination (beyond what she's already done)?
>  Does it react with biological stains that can distinguish between
>  material like collagen and bacterial films?

Oh yes. Schweitzer et al. did try antibodies against collagen, and they 
do react with the samples. The question is whether the collagen is 
contamination.

>  If genes and proteins from the environment are leaching into the
>  fossil, should'nt they also be in the surrounding rock, indeed, might
>  it be possible to detect higher concentrations closer to the surface
>  and outside the bones? Coring at the site might be informative in
>  that respect.

I don't think that has been done yet.