Does Dinosaur DNA still exist? -Part I

Iron from haemoglobin saved soft tissue in Dinosaur fossils?

As you know, fossils are actually a replica of the tissue once buried. So how can it be that scientist now find traces of soft tissue in the fossils?

When most animals die, nature likes to tidy up by making their bodies disappear. Very occasionally, though, the destructive processes get disrupted. This usually happens when the corpse is quickly buried by sediment deposited by a river or blown in by the wind. Then begins a slow process in which minerals precipitate from groundwater into the encased organic material, eventually replacing it with a stony replica: a fossil.

In recent years traces of soft tissue, such as blood vessels and bone cells, have been found in some dinosaur fossils. Now researchers have come up with an explanation for how these tissues were preserved for millions of years, which just might make it possible to extract some elements of prehistoric DNA.

 

 

In 2005 Mary Schweitzer, a palaeobiologist at North Carolina State University, found something unusual from a fossilised piece of Tyrannosaurus rex bone. Left behind were some fibrous tissue, transparent blood vessels and cells. Many argued that this material must have come from modern bacteria and not a T. rex, since nothing organic could possibly survive the 68 million years since the creature had walked the Earth.

 

 
In 2012, however, Dr Schweitzer and her colleagues went a step further, revealing the presence of proteins in a dinosaur fossil that had been freshly dug up and carefully protected from any potential contamination.

 

Moreover, one of the proteins the researchers identified could be found only in birds. Since dinosaurs were the ancestors of modern birds, the discovery made it hard to argue that soft-tissue material in the fossil could have come from bacterial contamination. Still, many scientists wondered how such a thing was possible.

 

Dr Schweitzer and her colleagues collaborated with a team led by Mark Goodwin, at the University of California, Berkeley, to seek an explanation. When sudiyng organic material from dinosaur with micro x-ray absorption spectroscopy, they notice something remarkable. The organic material in the samples was thickly laced with iron nanoparticles. In animals, iron is most commonly found in blood and this led the researchers to wonder if the iron had come from blood cells that had once flowed through their dinosaur’s veins.

 

Could this iron have played a part in the preservation of the tissues?

 

The researchers designed an experiment using freshly slaughtered ostriches which seemed to be a reasonable modern equivalent to dinosaurs. They extracted blood vessels from the bones of the birds and soaked them in a haemoglobin solution obtained from ruptured ostrich blood cells for 24 hours.

The samples were then placed in both a saline solution and sterile distilled water. As a control, some of the blood vessels were put straight into saline solution or water without being pre-soaked in blood.

 

As expected, the ostrich tissues that went directly into the water and the saline solution fell apart rapidly and were entirely consumed by bacteria or heavily degraded in just three days. The same thing happened to the tissue soaked in haemoglobin and placed in water.

But the treated sample in the saline solution remained intact and has stayed that way for two years now, with no signs of bacterial growth.

 

Dr Schweitzer and Dr Goodwin believe that highly reactive ions known as free radicals, produced by iron as it is released from the haemoglobin, interact with the organic tissue causing abnormal chemical bonds to form. These bonds effectively tie proteins in knots at the molecular level, much as the preservative formaldehyde does. This knot-tying makes the proteins unrecognisable to the sorts of bacteria that would normally consume them. This, they theorise, is how the soft tissues manage to survive for millions of years without rotting away.