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.