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…

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.   Yukon_C_2014Sml

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.

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Alan records the local stratigraphy while Tim extracts a squirrel nest from a permafrost face at Independence Creek mine site.

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A frozen Bison femur following sampling. The hard, light-coloured tissue in the bone and ice on the sample indicate that the DNA may be exceptionally well-preserved.

A team of paleontologists, lead by Dr Grant Zazula, is present during all the summer season to gather these precious remains, and this year, we were invited to sample frozen material directly on site for DNA study.

When it comes to ancient DNA studies, preservation of the samples is paramount to obtaining quality data, and bones taken from deep-frozen soil buried for thousands of years is dream material for us.

 

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The outstandingly-preserved mammoth molar. The indentations on teeth are often used for identification, but when you come across a tooth this size there is little question of its origin!

It is an amazing feeling to be digging through smelly muddy permafrost, in a gold mine, to extract a whole bison skull or a mammoth tooth from frozen soil, knowing that these samples are going to provide genetic data at the genomic scale, and helping us answer questions about the evolution of plants and mammals during and in between glaciation periods.

Stay tuned for more details on the different scientific projects based on the material we collected!

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