How fossil DNA could bring dying species back from the brink

Countless animal and plant species teeter on the brink of extinction, but the DNA of their ancestors may point the way to survival. Paleobiologists are scouring fossil DNA to determine why species once thrived...and how they can do so again.

Yes, it's the rare instance in which fossil DNA doesn't lead to cloning. Instead, scientists in the new field of "conservation paleobiology" are trying to glean all possible clues from the analysis of ancient DNA. For many species, there are even seemingly simple things that we don't know, like where that species lived a century ago, or how it managed to survive earlier drastic changes to its environment. Fossil DNA can reveal those answers.

Mike Bunce heads up the DNA Lab at Murdoch University in Western Australia. He explains what this new field aims to do:

"There are a variety of genetic tools now at the disposal of scientists, and these tools have had meaningful impacts in managing modern populations. It is only natural that this is now spilling over into the past to help us better understand things like biodiversity loss. If we're looking at re-establishing an ecosystem to what it formally looked like it's important that we know what used to live there not hundreds of years ago but thousands of years ago.

As an example of what their research has revealed, Bunce points to the woylie, a small marsupial currently confined to a small population pockets in Western Australia. But genetic research shows the creatures used to live all throughout Western Australia, interbreeding freely between different population. That's good news for rebuilding the population, says Bunce:

"We can tell that genetic signatures used to move around the entire south-west area. So we can't really get too precious about interbreeding these populations now because in the past they were definitely connected."

Then there's the case of the Tasmanian devil, which thanks to Saturday morning cartoons has become one of Australia's most famous animals. Over 70% of the species is affected by facial tumor disease, a contagious cancer that spreads between devils that share the same type of major histocompatibility complex, or MHC, gene. A particular variety of devil in northwest Tasmania has a different variant of the MHC gene than the rest of the devils, and this means they're able to launch an effective immune response against the cancer when the other parts of the species can't.

The question that paleobiologists are trying to work out is explained by ancient DNA expert Jeremy Austin:

"The important question is have devils had this disease for thousands of years and been surviving until they lost diversity when Europeans arrived? Or is it just an accident that the disease has turned up and taken advantage of the low diversity?"

Finding information like that can help distinguish between what are naturally occurring diseases and those that have been greatly worsened by human agency. But perhaps the most important use of fossil DNA is in determining how species respond to changes in climate. For this, experts have to look at animals from 10,000 to 18,000 years ago, as researcher Alan Cooper explains:

"That's where conservation paleobiology comes into its own,. You're taking information from the past, during, for example, periods of rapid climate change, to look at consequences that you can't gain from looking at the last few hundred years. The most surprising stuff ... is the incredible dynamism of the response of populations to climate: how violent it is; there are extinctions and migrations and replacements — huge see-sawing of populations. That's the kind of thing we absolutely need to know about if we're trying to predict what are the consequences of temperature change."

For more, check out Discovery News. Top image is a baby Tasmanian devil.