Woods’s lab used some of this abundant resource to settle a few mysteries about New Zealand’s lost ecosystems. Using a combination of ancient DNA, plant macrofossils, and pollen, his team reconstructed the diet of four moa species. They found that the heavy-footed moa preferred to graze in open fields and grasslands. The bush moa preferred to munch on forest understory. The giant moa was more of a generalist, moving between these two habitats at will.
Figuring out moa diet is only the tip of the dungheap when it comes to ancient poop studies. Prehistoric dung has a wealth of uses for science, from tracking the demise of the mammoth to deciphering the peopling of the Americas. The spores of Sporormiella, a type of mold that loves nothing better than a nice pat of dung to grow over, have been used as a proxy to track the abundance of megafauna across the millennia. Carbon dating DNA-fingerprinted coprolites from the Paisley Caves in Oregon helped prove the presence of pre-Clovis humans (and, as a bonus, testing feces for DNA doesn’t raise the same ethical quandaries as testing ancient skeletal remains).
The climate history of the American Southwest was established in large part thanks to a deposit of sloth dung discovered in Arizona in the 1950s. The dung was left by the Shasta ground sloth, a small species as ground sloths go, more bearlike than the more famous Megatherium, which grew to the size of an elephant. For around 30,000 years, these sloths used Rampart Cave, a hollow in the side of the Grand Canyon, as their latrine. Pollen in the accumulated droppings recorded the shifts in vegetation that accompanied the arrival and departure of past glacial maxima. Crucially, they proved that the shift in vegetation and temperature that came with the end of the last Ice Age wasn’t particularly new or extreme. It was something that had happened multiple times in previous millennia.
Tragically, the precious dung deposit caught fire in 1976. The National Park Service spent tens of thousands of dollars to save it, but to no avail. It made the nightly news. Walter Cronkite joked about “endangered feces,” but to Paul Martin, a geoscientist who devoted much of his career to reconstructing the environment of the ancient Southwest (and came up with the overkill hypothesis in the process) compared it to losing the Library of Alexandria.
Martin felt better a few years later, when two zoologists discovered an unusually big sphere of chewed-up grass in a cave in southern Utah. Subsequent visits turned up several more dung balls of surprising size, which radiocarbon dating showed to be about 12,000 years old. Martin guessed they came from America’s second-largest extinct mammal, the Columbian mammoth.
Larger than any living elephant, the Columbian mammoth, was, like them, a prodigious maker of dung. The Utah cave, named Bechan, from the Navajo word for “big shit,” showed just how prodigious. Excavations in the mid-’80s revealed a layer of dung 16 inches thick covering a surface of several tennis courts (that’s 14,000 cubic feet of dung total). This July, a team at McMaster University in Ontario reported that it had successfully sequenced DNA from the dung boluses, proving that they really did come from mammoths.