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Scientists who study our planet's past often have to piece together some pretty disparate clues. Fossils, artifacts, and other lines of evidence can often be few and far between.

So you can imagine how handy it would be to have an animal that collects clues from its environment and stores them away in a nice convenient spot. 

Meet the rock hyrax of Africa, a little animal that scientists love because it preserves pieces of the past in piles of poo. These furry little mammals live in and among rock crevices. They may look like rodents, but research has found that their closest relatives are actually elephants and manatees.

Rock hyraxes live in large colonies. And those colonies have developed the peculiar habit of using what are called communal latrines. Which is exactly what it sounds like: a designated spot that everyone in the colony uses for going to the bathroom.

These rocky toilets tend to be located in safe, sheltered areas, so a single latrine can last quite a while. In some cases, a latrine might be used by the same colony over hundreds of generations, forming a heap of waste that can be used for centuries. 

The end result is a midden, a multi-layered collection of fecal pellets in a substance called hyraceum, or the dried remains of hyrax urine. Which is something that was worth giving a name to. 

Because here's the thing: The hyraxes are only trying to keep their colony clean. But they unknowingly capture plant and animal remains from their nearby environment and preserve them in a time capsule. Which makes these poo piles a gold mine for researchers. 

Normally when we want to learn about how an ecosystem has changed over time, we look at biological and chemical evidence preserved in fossils, ice cores, or limestone cave formations. But in certain dry, rocky parts in Africa, those types of evidence are pretty rare. 

Hyraxes, however, are common. And so is their excrement. Which has led to a seriously impressive body of hyrax waste literature. 

Not only do hyrax middens preserve environmental data from the time the waste was created, they often do so in convenient chronological layers. Each time a hyrax lays down a fresh coat of urine, it seeps across rocks and around the poop pellets. And when it dries, it cements into a new layer of hyraceum crust.

In some places, hyrax middens can be over a meter thick and several meters across. And under the right conditions, a midden can become petrified and persist long after the hyrax colony has moved on. They can contain millenia of environmental history. And the oldest known hyrax middens preserve waste that's 50,000 years old.

Generally, hyrax middens contain a lot of plant material, since that what the little guys eat. And those plants can tell us a lot, especially about the climate and growing conditions that existed when they were eaten.

Like a 2010 study that looked at increase in leafy plants relative to grasses in two middens over the past 10,000 years or so. This suggested that the climate may have been drying out enough to make it hard for hyraxes to find lush, tasty grass to eat.

And there's more in those middens than just the plants hyraxes ate. Pollen grains are famously durable, and they can be preserved in middens when they drift in from the air or are carried on hyraxes' fur. 

In a 2011 study, researchers collected midden data from southern Africa spanning almost 20,000 years of history. This time, looking for ancient pollen.

The pollen revealed changes through time in fynbos, scrubby vegetation that makes up a unique type of plant ecosystem in southern Africa. The pollen record showed that past shifts in climate affected lowland fynbos more dramatically than the mountain varieties--data that might help researchers protect these endangered plants in the future. 

Research in hyrax middens has uncovered not only plant remains, but also ancient DNA from animals that shared the hyraxes habitat. And microscopic remains of charcoal that reveal local fire history. And all of this data can be combined with other information to reconstruct the history of Africa, and even of our own species. 

A 2018 study compared climate information from hyrax middens to archaeological records of human activity in south Africa over the last 20,000 years or so.

The data showed that as the regional climate grew drier coming out of the ice age, and large prey became harder to find, local humans changed their survival strategies. In many ways, they became less picky about their resources and went after more small animals like hares and tortoises, and they made their tools out of lower-quality, more common types of rocks. 

These changes reflect the amazing adaptability of our species in response to changing conditions. And this information is brought to us by the latrinal legacy of the hyraxes that lived alongside our ancestors. 

Africa is a continent of particular importance to the history of our own and many other species. And while there are midden-making mammals on other continents, it's hyraxes that provide a unique insight into Africa's past. 

Hyraxes and other midden-building species have been creating ecological time capsules for tens of thousands of years. They're the unwitting field assistants for today's scientists. 

It might not sound like the most glamorous job, digging through thousands of layers of an ancient latrine, but for scientists seeking to understand our world's history, there's nothing better than a bit of preserved hyrax waste.

But you don't have to go digging through hyrax middens just to learn stuff. For the rest of us, there's brilliant.org. If you like to challenge yourself every day, you might like their daily challenges.

Brilliant offers daily challenges which are questions about science concepts that challenge you to exercise your mind every day. None on hyraceum that we know of so far, but we'll keep you posted. Each question comes with illustrations, animations, or interactive visualizations and all the context you need to solve the problem yourself.

And if you find it peaks your interest, each one also ties back to a whole course offered by Brilliant. You can access each day's challenge for free, but a premium membership unlocks the whole archive. And conveniently, the first 200 people to sign up at brilliant.org/scishow will get 20 percent off an annual premium subscription.

So check it out and see if it's right for you. And thanks for your support. 

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