They were some of the largest, hairiest animals ever to walk the Earth, but new research shows a big part of the woolly mammoth's diet was made up of tiny flowers.

The work by Eske Willerslev, a researcher at the University of Copenhagen, is based on DNA analysis of frozen arctic soil and mammoth poop. It suggests that these early vegans depended on the flowers as a vital source of protein. And when the flowers disappeared after the last ice age, so too did the mammoths that ate them.

But not everyone sees the relationship between disappearing flowers and disappearing mammoths the way Willerslev does. Professor Daniel Fisher, a paleontologist at the University of Michigan, said the new work, published in the journal Nature, does show that both vanished around the same time. But he also studies mammoth poop. And it makes great fertilizer. So maybe it was the other way around: the flowers needed the mammoths' poop to grow, so when the mammoths started to disappear ...

"It becomes difficult to sort out what part of it is cause, and what part of it is effect," Fisher said. He also points out that present-day elephants can survive just fine on grass and shrubs.

So if it wasn't the disappearing plants, what was causing mammoths to vanish? Fisher suspects it was us. We were around, and while the mammoths were eating the flowers, we were eating the mammoths.

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