Lifting up the toilet seat and finding some old, dried pee would generally yield a reaction of “ewww!”
But that’s nothing to Brian Chase, a researcher at Montpelier University in France. Chase prefers pee of a somewhat older vintage: the crystallized pee of the rock hyrax (Procavia capensis) that dates to some 55,000 years ago.
Chase uses the information gathered from crystallized hyrax pee in southern Africa to study Earth’s climate thousands of years ago. Not only does this data give scientists a better idea of what the planet was like back then, it also helps them better understand how Earth’s climate is currently changing and what might happen in the future. (Related: “6 Ways Climate Change Will Affect You.”)
For instance, new analysis of the pee reveals that, as Arctic glaciers melted at the end of the last Ice Age around 12,000 years ago, temperatures in southern Africa warmed dramatically, Chase said during the annual meeting of the American Association for the Advancement of Science in Boston earlier this month.
His previous data had found that the Southern Hemisphere was drier than predicted by climate models following dramatic climate changes around 5,500 years ago.
In a study published in 2011 the journal Geology, his team found that when the Northern Hemisphere warms, the extreme Southern Hemisphere cools, and vice versa.
“This has important implications for our understanding of how the earth system operates, and how we can expect it to respond to different forces, both in the past and the future,” he said. (Also see “Urine Vision? How Rodents Communicate With UV Light.”)
Layers of Pee
Cute, cuddly critters that are roughly the size of rabbits, hyraxes eat mostly leaves and grasses and are found across Africa and the Middle East. Despite their small sizes, they are the closest living ancestors to elephants and sea cows.
What makes hyraxes useful to scientists are their peculiar bathroom habits. A group of hyraxes will urinate and defecate in the same place, known as a midden, for generations at a time. (More pee news: “Turtles Urinate Via Their Mouths—A First.”)
Because hyraxes live in relatively dry areas, their bodies help to conserve water by making their urine fairly thick and sticky. This stickiness means that pollen and plant material can become trapped in the hyrax pee as it dries. Generation upon generation of hyraxes all pee in the same place, sometimes for tens of thousands of years.
Each generation of hyrax creates its own new layer of pee that captures the local pollen and plants as it dries. In some of the oldest and largest middens, the crystallized pee forms a structure that is 67 inches (170 centimeters) high—providing a wealth of data for scientists.
“This exceptionally high accumulation rate … means we will be able to get a subdecadal record of environmental change spanning much of the Holocene,” which refers to the last 11,700 years of Earth’s history, Chase told Weird & Wild. (See a prehistoric time line.)
Unlocking Pee’s Secrets
To study ancient climates, scientists generally study the traces of plant material found in soil samples from lakes, bogs, and other soggy grounds.
The wetness in these areas prevents the full decomposition of plants, which means scientists can identify them thousands of years later. Southern Africa, however, has been historically quite arid. So, without lakes and streams from which to gather samples, researchers have had to guess at what the ancient climate was like.
Crystallized hyrax pee, however, changes that.
For one, Chase and others can now use the chemical signatures in the pee to get an idea of what the hyraxes ate when they were alive. (Also see: “Fossil Sea Cow Teeth Reveal Steamy Ancient Earth.”)
As well the tiny pieces of debris and pollen frequently found trapped in the ancient pee can tell scientists what types of plants were nearby.
This is useful because knowing what plants lived at the time can give researchers a good idea of what the climate must have been like. Some plants, like grasses, need lots of water to survive, while other plants are much more drought-resistant. The chemical signatures of water the plants “drank” while alive also give scientists an idea of how wet the area was.
That’s because hydrogen in the ancient water has different isotopes—or different masses—that can tell scientists what kind of precipitation was present at the time. For instance, if the team were to find a lighter isotope, that would indicate a rainy environment.
Taking the Piss
Getting to the hyrax pee, however, poses its own unique set of problems. Hyrax middens are frequently hidden behind sheer rock faces and in some very tight quarters. While it’s good for the samples—being that sheltered means the pee doesn’t wash away if it rains—it’s difficult for the scientists to access.
Chase, an avid rock climber, puts his skills to good use scaling rock walls. Then, he uses a variety of power tools to grab some samples of the crystallized pee to take back to the lab.
“Once we have found a good layer of solid urine, we dig out samples and remove them for study,” Chase told The Guardian last week.
“We are taking the piss, quite literally—and it is proving to be a highly effective way to study how climate changes have affected local environments.”