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Llamas can still be found at Machu Picchu today (image courtesy of flickr user Santiago S.V.)

The Incas dominated much of South America for centuries, building a vast empire that stretched high into the Andes where the terraced city of Machu Picchu still inspires wonder. Now scientists in France and Peru, reporting in the journal Antiquity, reveal what made it all possible: llama dung.

The researchers analyzed mud cores from the bottom of a lake near the Incan town of Ollantaytambo in Peru. These sediment samples contain a record of past environmental conditions in the area. (In some places, scientists have found cores that give records stretching back tens of thousands of years). In the Peruvian sample, the researchers found a sudden increase in maize (corn) pollen starting around 2,700 years ago. Unlike the wild-grown quinoa that the Incas had previously relied upon to survive, cultivated maize provided more energy and could be stored or transported long distances, perfect for fueling a growing empire. But how were they able to grow maize high up in the mountains?

The mud samples also provide that answer. About the same time that there was an increase in maize pollen, there was an increase in oribatid mites, tiny insects that live in soil and feed on feces. The researchers conclude that dung from llamas—which the Incas had domesticated hundreds of years previously—provided food for all those mites. Llamas “defecate communally so [their dung] is easily gathered,” Alex Chepstow-Lusty of the French Institute of Andean Studies explained to the Guardian. The Incans could then use the poop as fertilizer for their maize fields, which reached elevations up to 11,000 feet above sea level. “This widespread shift to agriculture and societal development was only possible with an extra ingredient—organic fertilizers on a vast scale,” Chepstow-Lusty says.

A mummified princess from Thebes (known as Luxor during her time) is the earliest person known to have had coronary heart disease (courtesy of flickr user Rita Willaert)

You might be under the impression that hardening of the arteries, a.k.a. atherosclerosis, is a modern problem. That our diets, rich in animal fats and processed foods, are the problem, and if we only ate like humans used to not so long ago, we’d have no need for bypass surgeries and no one would ever die of a heart attack. But atherosclerosis is common in Egyptian mummies, say scientists who imaged dozens in Egypt, going as far back as 1550 B.C. (Their study, recently published in the journal Cardiovascular Imaging, was presented at the International Conference of Non-Invasive Cardiovascular Imaging earlier this week.)

The researchers created CT scans of 52 ancient Egyptian mummies at the National Museum of Antiquities in Cairo (the mummies couldn’t leave, so the scans were done at the museum). They could see arteries in 44 of the mummies. Of those, 20 had calcification, a marker for atherosclerosis, in their arteries, and in three of the mummies that calcification could be seen in coronary arteries.

Calcification in the right (RCA) and left (LCA) coronary arteries appears white in this CT scan (courtesy of the European Society of Cardiology)

The mummies with signs of atherosclerosis tended to be those that had lived the longest; they averaged 45 years old. One of the three with coronary heart disease was the princess Ahmose-Meryet-Amon, who lived in Thebes around 1580 to 1530 B.C. and died in her 40s; two of her three main coronary arteries were blocked. If she had lived today, “she would have needed bypass surgery,” said one of the study’s co-authors, Gregory Thomas of the University of California, Irvine. She is now known as the earliest person in history to have suffered from coronary heart disease.

At the time when the princess lived, the Egyptian diet consisted of fruit and vegetables, bread, beer and a little domesticated, lean meat, which may sound like a doctor’s recommendation for how to avoid the very problem the princess had. So how did her arteries end up with so much calcification? The researchers have a couple of theories. Parasitic infections were common in ancient Egypt, and the resulting inflammatory response may have predisposed her body to atherosclerosis, much as HIV appears to do so today. Foods during that time were often preserved in salt, which could have had an adverse effect. Or the princess may have eaten a different diet than the average Egyptian; as a royal, she could have feasted on luxury foods like meat, cheese and butter, the very items that heart doctors tell us to avoid.

George Pollard Jr. was not a very lucky sea captain. In 1819, he became captain of the whaling ship Essex, out of Nantucket, Massachusetts, and headed for the Pacific Ocean. Just four days out, though, a storm struck and damaged the ship. Still, Pollard pressed on, rounding Cape Horn in January 1820 and then sailing north. Worse luck struck in November, when the ship was rammed twice by a large sperm whale. The Essex sank, and the crew piled into the small whaleboats with as much supplies as they could carry. It wasn’t enough, however—many men died and some had to resort to cannibalism to survive. The first mate wrote an account of the ordeal, and it inspired Herman Melville to write Moby Dick about Captain Ahab and his quest for the white whale.

When Pollard returned to Nantucket, he was given command of another whaling ship, the Two Brothers. And his back luck held. On the night of February 11, 1823, the ship struck a shallow reef off French Frigate Shoals, about 600 miles northwest of Hawaii. The crew members fared better that time, at least, and were rescued the next day by another Nantucket whaling ship. But Pollard’s career as a whaling captain was over. He made one trip on a merchant vessel and then spent the rest of his life as a night watchman, safe on dry ground in Nantucket.

A diver examines an anchor from the Two Brothers (credit: NOAA)

The Two Brothers remained hidden on the bottom of the sea until 2008 when marine scientists went on an expedition to the Northwestern Hawaiian Islands to study the marine life there. This area is part of the Papahānaumokuākea Marine National Monument, 140,000 square miles of protected ocean and one of the world’s largest protected areas.

Divers on the expedition first spotted a large anchor, the first clue that there might be some bigger find on the seafloor. Then they found other items, such as cast-iron pots, called trypots, of the type used to melt whale blubber, indicating that it wasn’t just any old wreck; marine archaeologists concluded that they had found a whaling ship.

Expeditions in 2009 and 2010 turned up items such as ceramics and glass that helped the scientists date the wreck, and first-hand accounts from sailors who had been on the Two Brothers approximately matched the location of the find. Now the scientists are ready to publicly conclude that the wreck was Captain Pollard’s ill-fated ship.

This is the first wrecked Nantucket whaling ship to ever be found, which is rather amazing considering how many hundreds of those ships were in existence during Nantucket’s whaling heyday in the 1700s and early 1800s, and how many must have sunk; whaling was never a safe occupation. “Shipwreck sites like this are important in helping tell the stories of the early days of sailing, including whaling and maritime activities both in the Pacific and around the world,” said Papahānaumokuākea Marine National Monument maritime archaeologist Kelly Gleason, who led the expedition.

Is your office rather empty this week? Looking for something to read to fill the time? How about some great science and nature stories from Smithsonian? Here are my ten favorites from the past year:

Did you read the cover story about lions?

The Truth About Lions (January): Staff writer Abigail Tucker visits Craig Packer, who has been running the Serengeti Lion Project, the most extensive carnivore study ever conducted, for more than three decades. In Tanzania, these kings of beasts are on the decline because of one pervasive problem—people.

The Human Family’s Earliest Ancestors (March): New fossil finds in Africa are expanding the human family tree and changing what we think about what our earliest ancestor’s looked like and how they moved.

Dark Energy: The Biggest Mystery in the Universe (April): Seventy-three percent of the universe consists of dark energy. Writer Richard Panek traveled to Antarctica to see how scientists are trying to discover just what that mysterious stuff is.

How Our Brains Make Memories (May): Our memories aren’t as permanent and unchanging as we may think (or like), but this idea has important implications for dealing with post-traumatic stress disorder.

A Puffin Comeback (June): A biologist is testing methods for reintroducing bird species by luring puffins, those adorable black-and-white birds with outsized, stripey beaks, back to Maine.

Jellyfish: The Next King of the Sea (July/August): Fish, coral and plenty of other sea creatures—including most of the tasty ones—aren’t doing so well under threats like ocean acidification. But jellyfish are thriving and appear poised for a takeover.

The Origins of Life (October): Scientists have a good idea of how evolution works, but how life began is still fuzzy. Writer Helen Fields visited a mineralogist who thinks he’s figured out where to look for the origins of life—rocks.

The Colorado River Runs Dry (October): The Colorado River ran from the Rockies to the sea for six million years. Why doesn’t it now? Dams, irrigation and climate change.

How Male Elephants Bond (November): Biologist Caitlin O’Connell-Rodwell writes about her research findings that male elephants are far from loners. They have a complex society of their own.

Dinosaurs’ Living Descendants (December): Fossil finds in faraway China have been key to the conclusion that modern birds evolved from dinosaurs millions of years ago.

Local science writers look for fossils on a block of stone that is part of the Duke Ellington Bridge.

This past Saturday, geologist Callan Bentley, of Northern Virginia Community College, led a couple of dozen local science writers on a trip back through Washington, D.C. history. We didn’t learn about Abe Lincoln or George Washington, though. This was geological history, a record of events that occurred hundreds of millions of years ago.

An interesting tangent to our field trip took place on the Duke Ellington Bridge as we walked across Rock Creek Park. The bridge, like many of Washington’s structures, is made of blocks of stone (often from faraway states; Indiana in the case of the bridge). These blocks, Bentley pointed out, are often full of fossils. You just have to look for them. (But a little knowledge is probably helpful; I never would have spotted the fossils on the bridge if Bentley hadn’t been pointing them out to us.)

A close-up shot of the fossil-bearing bridge block.

It seems a person could take a really interesting tour of geological history without ever stepping inside a museum here in Washington. If you don’t believe me, check out dcfossils.org. A local geology enthusiast, with help from people like Bentley, has been cataloging Washington’s architectural fossils—fossils that can be found in the building blocks that are part of buildings, monuments and bridges—photographing them and writing about the locations and the fossils you’ll find there. The blocks that make up the National Museum of the American Indian, for example, are made of Kasota Limestone from Minnesota. Look closely at some of the stones and you can find tube-like patterns created by invertebrates as they traveled through the mud at the bottom of a deep sea that covered Minnesota around 480 million years ago during the Ordivician period.

Washington isn’t alone in its wealth of architectural fossils. There are fossils in the stones that make up Baltimore and Montreal. The Maine State Capitol has them, too. Every city must have collected fossils in its building blocks. Maybe they’re even in your home. You’ll just have to look.

Photos courtesy of Helen Fields.