DNA traces in soil link a suspect to a crime scene

By Jennifer Young

During my PhD at the Australian Centre for Ancient DNA (ACAD) I developed a new soil DNA technique for use in real-life forensic casework. The study, now published in Forensic Science International, has shown that DNA identification of the fungi, plants, and bugs in small samples of soil can link a person to a particular location.

Like a fingerprint, the life invisible to the naked eye reveals the original location of soil.

The project, co-funded by the Australian Research Council and the Australian Federal Police, created a mock crime scene to mimic the disappearance and recovery of a woman’s remains. A shovel was used to dig a shallow grave before being placed into a car boot alongside shoes worn at the time.

Six weeks later, the DNA of the fungus, plants, and bugs living in the soil stuck to the shoes and shovel was recovered, and compared to DNA detected in soils from multiple other locations across South Australia. The unique signature of fungus, plants, and bugs placed the soil samples recovered from the shoes and shovel just meters from the crime scene. This study is one of the first to demonstrate that new genomic methods can be used in real-life applications to track criminals weeks later and accurately place them at crime scenes. Our murderer has a lot more explaining to do!

What happens at Camp, stays at Camp… or does it?

by Tim Rabanus-Wallace

Tim presents a snapshot of life on the Dawson Field Camp during the July 2014 Yukon field expedition, introduces you to the crew, and talks about some of the considerations that go into ancient DNA fieldwork.

Digging up frozen bones in gold mines

by Julien Soubrier

As part of our research on the evolution of flora and megafauna throughout the climate variations of the late Pleistocene (~10 to 100 thousand years ago), we had the opportunity to collect frozen bone remains directly from the permafrost in Canada. Three of us traveled to the gold rush city of Dawson in the Yukon, where a few families are still mining for gold in the frozen soil. To reach the gold-rich layers, miners are using high-pressure water to accelerate the natural thawing of the permafrost, uncovering numerous bone remains in the process. Most of these bones are from large mammals who were grazing in the steppes of the Berigian region a few millennia ago: mammoths, horses, bison…

  

Above: Placer mining. Recycled water is pumped into the mine face at high pressure, melting the ice and revealing the gold-bearing gravels. After a claim is worked in the way, miners reform the land using excavators, allowing local plants to recolonise, and the environment to rapidly recover.

Natural Trap Cave: First instalment of year 1 of the field project.

by Alan Cooper

Having rigged the cave on the first day, I guess it was appropriate that I was the one to take the first descent into the chasm below. It’s caving lore something along the lines of the Captain going down with his ship – if you rigged it, you should be first to ‘test’ it out! Backing over the ledge and unlocking my brakebar, I descended about 3 m against a series of ledges – before dropping into open space. Looking around I could see several enormous nests, around a metre wide and made of big branches – eagles had obviously lived under the overhang of the cave entrance for many years, presumably until the grid was placed over the entrance. I’ve not seen eagle nests up close before and it was impressed how large they were. Pack rats were also nesting around these ledges – 100ft over space, and we saw several snake skeletons down in the cave attesting to the effective security systems surrounding their home!

If it walks like a duck and quacks like a duck: it’s probably a duck. But ancient DNA can do better than that…

By Kieren Mitchell

Animals that have evolved on islands become adapted to very specific and stable environments, leaving them extremely vulnerable to outside disturbances. For example, many island birds became flightless in the absence of predators (most famously the dodo). Consequently, these species frequently become extinct soon after the arrival of humans, through either direct (e.g. hunting) or indirect actions (e.g. habitat destruction, introduced species). This gives us very little opportunity to study these creatures, and means that their origins and evolutionary relationships are often unknown (e.g. Sylviornis from New Caledonia). Ancient DNA analysis is a valuable tool in unravelling the history of these mysterious species.