News in Science

Ancient dung heaps are genetic time capsules

Time capsule DNA extract from ancient latrines has "opened the door" to identifying the plants and animals that existed in northern Australia's remote Pilbara region more than 30,000 years ago.

Significantly, says co-author Daithi Murray, of Murdoch University's Ancient DNA Laboratory, the genetic material has been collected from what is believed to be the oldest sample yet uncovered in Australia's arid environment.

In a paper published recently in the journal Quaternary Science Reviews, Murray, doctoral student, and colleagues detail their success in extracting ancient DNA from four locations - three in Western Australia and one in South Africa.

The West Australian samples come from "middens" - a hard, impermeable amalgam that is formed over centuries from the accumulation of faecal matter and organic material such as plant and animal tissue.

The fossil middens were located in the Brockman Ridge in the Pilbara, Young Range in the Gibson Desert and Cavenagh Range in the Central Ranges.

Murray says the fossil middens consist of material from the local environment used for construction of the nest, or for food by the midden's host.

This means they contain detailed information about the plants and animals present in the localised area at the time.

All of the middens in the study have previously been analysed for pollen and macrofossil remains allowing the researchers to assess the effectiveness of DNA techniques in providing further information.

New species uncovered

He says a range of plants and animals, some of which are now locally extinct, were detected, such as the common brushtail possum found in one midden in the Cavenagh Range, which was last seen in the region in the 1930s.

Importantly the technique also led to the identification of plants and animals that had previously gone undetected in the earlier types of studies, such as a range of previously indistinguishable arid zone grasses.

Murray says the study of ancient DNA has until now been limited to cool and frozen environments because the extreme conditions of arid climates such as the West Australian desert led to severe degradation of samples.

However he says their study shows ancient DNA can be successfully extracted from these fossil middens, giving an insight into the ecology of the environment as far back as 30,000 years ago.

Changes over time

"There is very little ecological data from that time," says Murray. "The success of the study shows middens can be a very valuable resource that opens the door a little more."

Murray says the study of past and present arid zone environments, and the distribution of species within them, allows for the exploration of how these species have adapted and shifted in response to both natural and anthropogenic changes.

"Put simply, we cannot monitor environmental change if we have no baseline to compare it against - these middens provide the time capsule we need to make those comparisons in the arid zone."