Fossilized dung contains surprising lessons, including details of the family history and diet of ancient cave hyenas, according to a new study.

Scientists extracted DNA from two fossilized cave hyena spoors, or coprolites, collected at the Coumere Cave in France and found that there's little difference between the extinct cave hyena and the modern spotted hyena, according to a paper published Wednesday in the Proceedings of the Royal Society Biological Sciences.

From a genetic point of view, the cave hyena is the Eurasian representative of the Pleistocene spotted hyena rather than a distinct species, the researchers wrote.

The researchers also found DNA from red deer in the cave hyena excrement, a potential leftover from a meal long ago.

Fossilized hyena droppings have also yielded insights into ancient humans. In 2009, anthropologists unearthed the oldest recorded human hairs from the feces of a brown hyena that lived between 195,000 and 257,000 years ago.

Turns out dung can be a useful research tool. Anthropologists used excrement to trace the trail of human migration. In 2008, scientists announced that they had found 14,300-year-old fossilized human feces in North America, challenging a long-held theory that humans first arrived on the continent by walking across a land bridge from Asia to Alaska.

One of the largest pieces of fossilized ancient human waste ever discovered was found in 1972 in England on the site of an ancient Viking settlement that now houses a bank. Analysis of the Lloyds Bank coprolite showed that whoever passed the feces lived on mostly meat and bread and had a bad case of intestinal parasites.

Extracting DNA from a fossil, whether it started out as a bone or as feces, is easier if the fossil has been buried in a cold, dry environment - the ideal specimen would be one that has been frozen in ice.

Sometimes scientists get lucky- as Mary Schweitzer of North Carolina State University did when she cracked open Tyrannosaurus rex bones and found remnants of soft tissues.

Many scientists were skeptical of Schweitzer's find, saying it was impossible for even tiny bits of flesh to survive for 6 million years. Last June, Schweitzer and several colleagues argued in a paper in the journal PLoS ONE that the collagen she found could have survived because its component tiny fibers were so tightly wound up.

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