When scientists around the world think of dung, they think of Jim Mead. Mead, a researcher at Northern Arizona University (NAU), is one of the world's foremost authorities on animal dung, and he's got the poop to prove it. 'You have got to laugh at this bizarre resource,' says Mead, director of NAU's laboratory of quaternary palaeontology.
'Although I don't think anyone is keeping track, I suspect we have the largest comparative animal dung collection in the world. If someone needs to identify dung, they send it to me.' The lab, part of the university's centre for environmental sciences and education, has row after row of cabinets with thousands of dung pieces used by scientists to get accurate data on an array of topics, including the environmental changes that took place on the Colorado Plateau during the last 100,000 years.
'Dung is accurate for carbon dating,' Mead explains. 'It's a data set that typically disappears in the fossil record. All we typically get are bones, but with dung we get biochemistry. We can tell a lot about the climate by analysing what plants the animal ate.' Through the digested plants, scientists can tell what was going on in the environment at the time, such as the amount of rainfall that was occurring.
The data help researchers pinpoint when different changes in the environment took place. 'The plant remains in the dung allow us to determine the mosaic of plants in the local plant community. The community structure changes with changes in climate,' he says. Mead's research includes tracking and comparing ancient dung DNA samples to learn about an animal's gender, food and water sources, air pollen, parasites and community structure during the Ice Age.
The data allow him to determine when and how an animal evolved and became extinct. The collection includes dung from modern animals to prehistoric ground sloths and 40,000-year-old mammoths. Molecular biologists in Denmark, Australia and Canada are using pieces from NAU's dung collection to compare its DNA to dung they are finding. 'To understand ancient dung, one must have a modern comparative collection, and we have one of the best there is,' Mead notes.
'It is extremely rare to have preserved fossil dung - yet we have the best and most there are in any collection - from Siberia to Tierra del Fuego to Argentina - we have it.' Most of NAU's dung collection is dried and stored wrapped in tissue inside sturdy, archival cardboard boxes. Mead opens a box of chunky 14,000-year-old mammoth dung and a slight scent of musty grass escapes.
He points to the chomped blades of grass fossilised into the brown dried dung and surmises that the mammoth ate about 600 pounds of grass a day. Mead currently is working with the Unites States of America's National Park Service to figure out when bison were introduced to its plateau region.
Previous research suggests bison dispersed into the Grand Canyon area more than 11,000 years ago, but with dating from dung, Mead knows that they roamed the plateau at least 23,000 years ago. He also curates dung and skeletal collections for 22 national parks. Dung from the NAU collection also finds its way into public displays in museums, including the International Wildlife Museum in Tucson, Mesa Southwest Museum in Mesa and at the National Museum in Paris.
'It's no coincidence this dung collection is here,' Mead says. 'The Colorado Plateau is arid and replete with shelters and caves that are perfect for dung collection. Most other places in the world stay moist and the bacteria break down the dung.' Mead began collecting dung during his research at the University of Arizona in the 1970s.
When he came to teach at NAU in 1985, Mead brought the collection with him and has since grown it by gathering dung from zoos and remote regions throughout United States and in places such as Africa, Canada, Mexico, South America, Australia and Siberia. 'Although our research is humorous,' Mead says, 'the data from dung is nothing to laugh about.'