A new study, conducted by a large consortium involving more than 30 groups from the United States, Canada, Australia and European countries, provides a unique view of the diet of giant Ice Age animals such as woolly mammoths, bisons, horses and woolly rhinoceroses.
This is an artist’s rendition of a woolly mammoth. Image credit: Flying Puffin / CC BY-SA 2.0.
The team sequenced DNA taken from samples of frozen soils and the stomachs of creatures preserved in the permafrost of Siberia and Alaska-Yukon.
“Permafrost (ground that remains at or below 0 degrees Celsius for two years or more) acts like a giant freezer, preserving countless plant and animal remains from which we can build a record that covers millennia,” said Prof Julian Murton from the University of Sussex, UK, who is a co-author of a paper published in the journal Nature.
“Permafrost is ideal for this kind of study because the DNA isn’t lost to the normal processes of decay,” added co-author Prof Mary Edwards from the University of Southampton, UK.
The permafrost sediments being studied consist of silt and sand rich in organic carbon and ice. These sediments are known by the Russian term yedoma and occupy a region of about 1 million square km in central and eastern Siberia, as well as large parts of central and northern Alaska and the Klondike region of Yukon, Canada. Collectively, these areas represent the Ice Age subcontinent of Beringia, which included a wide land bridge linking Siberia to Alaska.
Until now, analyses of vegetation over the past 50,000 years has been based mainly on studying fossil pollen, showing that vegetation in cold environments, supporting large herbivores, was mainly made up of graminoids – plants such as grasses and sedges.
However, new analysis challenges this view. It reveals that the dry steppe tundra on which the animals lived and fed was dominated by forbs – herbaceous flowering plants usually found in grasslands, meadows and tundra, which provided more nutrients to the grazing animals than grasses.
One such forb whose Ice Age DNA remains occur in Siberian permafrost is Plantago canescens (Northern Plantain).
After the Ice Age ended about 10,000 years ago and many of the megafauna became extinct the forb-rich vegetation was replaced with moist tundra vegetation dominated by woody plants, grasses, sedges and mosses.
“Analyzing plant DNA has provided us with a unique perspective on this now extinct northern ecosystem and given new insights into how such large animals could survive extreme cold and harsh ice-age conditions,” Prof Edwards said.
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Eske Willerslev et al. 2014. Fifty thousand years of Arctic vegetation and megafaunal diet. Nature 506, 47–51; doi: 10.1038/nature12921
