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6 March 2014 1:04 pm ,
Vol. 343 ,
- 6 March 2014 1:04 pm , Vol. 343 , #6175
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ScienceShot: Ice Age Creatures Grazed More Than Grass
5 February 2014 1:00 pm
Mammoths and other creatures that grazed arctic environments during much of the last ice age were eating more than just grasses, a new study suggests. Previous research, which typically relied on identifying and counting the grains of pollen trapped in ancient sediments, have suggested that most vegetation that graced the arctic tundra and steppe belonged to a class of plants called graminoids (which includes grasses, reeds, and sedges). But when researchers analyzed more than 240 samples of permafrost drilled from 21 sites in Scandinavia, Siberia, Alaska, and Canada, they found DNA from a wide variety of plants (including forbs, which typically are protein-rich, herblike plants that don’t produce much pollen). They also found the DNA of nematodes (roundworms), which helped the researchers infer the types of plants inhabiting the area at the time. The amount and type of genetic material, along with carbon dating of the samples, reveal that between 50,000 and 25,000 years ago—before the peak of the last ice age—arctic vegetation consisted mainly of forbs, the researchers report today in Nature. During the coldest part of the ice age (25,000 to 15,000 years ago), the number of forb species declined markedly, but the plants still outcompeted grasses. Only within the last 10,000 years, after the ice age ended and relatively moist conditions returned to the arctic, did nutritious forbs yield to less nourishing plants such as graminoids and woody shrubs. The dominance of forbs prior to the end of the ice age may help explain how the frigid tundra and steppe environments could support large herds of humongous herbivores such as mammoths (background of artist’s representation), reindeer, and musk oxen, the researchers contend.