What most of us think of as fossils are the inorganic parts of animals (those parts that don’t rot, such as bones made from calcium) preserved with minerals that have replaced the original organic material.  Organic compounds, generally, are those that contain carbon:  examples are flesh, skin and hair.  Inorganic compounds do not contain carbon:  mature bone is 65% calcium phosphate and this is why bones do not decompose in the same way as flesh.

 

Late in 2013 a female mosquito fossil, dating from 46 million years ago, was found in shale deposits in what is now the US state of Montana.  There is an image of this in the section 'the Jurassic Mosquito'.  Researchers could see that the gut of this mosquito was distended, and they were able to detect high levels of iron in the abdomen.  Using a non-destructive technique called mass spectrometry, they were able to find haem, a component of haemoglobin, the compound that is responsible for the transport of oxygen in red blood cells. 

 

This is exciting news, as it raises the possibility that even older fossilised insects might exist, complete with blood-filled abdomens, but does it mean that it might be possible to extract DNA?  Surely, because it is organic, DNA will decay?