Soft tissue preservation

Soft tissue preservation is when, during the process of fossilisation, soft tissues are preserved. For various reasons, soft tissues (i.e. non-bones) do not usually survive in fossils, but it does happen from time to time.

Varieties
This can happen in a number of different ways:

Mineralised tissue
Normally, fossils become fossils&mdash;and not just a pile of bones in the ground &mdash; via a process called mineralisation. This is when the material that makes up the corpse is chemically altered and becomes non-organic.

In most cases bacteria get to the fossil before this process takes place, stripping the meat from the bone. Consequentially, the norm is for only the bones to be preserved.

However, in some circumstances the soft tissues will also be mineralised. The fact that this is still referred to as 'soft tissue preservation' confuses people to no end.

Traces, residues and impressions
Sometimes &mdash; rather than being preserved as above &mdash; tissue such as skin or feathers may leave impressions or other traces in the rock. Many dinosaurs are known to have had feathers because of this kind of preservation: we know, for example that ' and ' did because of the discovery of quill knobs in fossils.

Also fitting under this category are tiny residues of proteins and other organic molecules surviving the millennia in sheltered cracks in bones, etc.

Not-all-that-soft tissue
Considering that the simplest definition of "soft tissue" is "organic material that isn't bone", there's an awful lot covered by the term that doesn't really belong in the same category as muscle fibres, for example. The polysaccharide known as chitin is one such 'hard' soft tissue &mdash; it is what makes up the exoskeletons of crustaceans and insects, and the cell walls of fungi.

It should come as no surprise that, like bone, chitin can and will mineralise and fossilise. However, it also has the potential of simply surviving &mdash; in certain circumstances, like the residues above &mdash; the millions of years required to be discovered by paleontologists. One of the oldest discovered examples of chitin preservation was of a 34.36 million year-old cuttlefish, the latching on to which by a group of young-Earth creationists naturally incurred the wrath of PZ Myers.

Organic tissue
On rare occasion, as alluded to in the above categories, organic tissue will survive unchanged by the millennia. However, as a general rule, this becomes even rarer as time goes on since the organism died. Common mechanisms include freezing in glaciers and permafrost, preservation in amber, burial in anaerobic conditions, and general inaccessibility to microbes.

Organic molecules&mdash;if left undisturbed for thousands if not millions of years&mdash;are believed to spontaneously degrade into their component, smaller molecules. However, there is little consensus within the scientific community as to how long this takes. In many cases, traces of organic tissue have been discovered in fossils many millions of years older than the upper limit allowed for by lab experiments. You can see where this is going, can't you?

Creationist claims
This apparent impossibility is repeatedly seized upon by creationists to "prove" the young Earth. There are a number of more notable incidences of this, but one will note that should a fortnight go by without a creationist news outlet trumpeting some study or another on this subject we will know that we have won the culture wars.

The common thread in this claim is the great irony of creationists dogmatically adhering to the results of lab studies using uniformitarian preconceptions of processes lasting millions of years which nobody has directly observed.

The Schweitzer fossils
They treat you really bad, they twist your words and they manipulate your data.

The work of non-creationist Christian palaeontologist Mary Higby Schweitzer has become a magnet for creationists.

Her first appearance above the parapet came in 1993, claiming the discovery of collagen in a T. rex fossilized bone dated at 68 million years old. Arguments about whether or not the discovery is the genuine article has raged within the scientific community ever since, Dr. Schweitzer for her part having supported her case with her discovery of a second tissue-containing bone in the meantime. The creationists, of course, have picked up on it without qualms.

Published Reports of Original Soft Tissue Fossils
In July of 2011 Brian Thomas compiled for the Institute for Creation Research a list of "Published Reports of Original Soft Tissue Fossils." He found 38 examples of "Articles Published in Peer-Reviewed Journals" and 4 "Preliminary Reports Published Elsewhere" (known to the rest of the world as newspaper articles/science by press release).