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In 17000-year-old puma poop, a glimpse of Ice Age parasites - NOVA Next

20 September 2019

Even after thousands of years of lying around, crap can tell quite the tale. Reporting this week in the journal Parasitology, a team of archaeologists sifting through a knob of puma poo has extracted a 17,000-year-old sample of DNA from Toxascaris leonina, a roundworm that still plagues felines today.

In addition to providing humankind with its oldest example of parasite DNA to date, the dessicated dookie raises some questions about the disease ecology of these big-bodied cats. In modern times, Toxascaris is a common intestinal tenant of domestic cats and dogs, which can transmit the worm to their wilder cousins. But the study’s findings suggest that prehistoric pumas must have had some other way of picking up the parasite: The poop’s timestamp predates the earliest known human settlements in the region, presumably clearing people and their pets of blame.

The team behind the discovery first stumbled upon the fossilized feces in the sediments of a rock shelter in Argentina’s Catamarca Province, nearly 12,000 feet above sea level. Radiocarbon dating revealed that the deuce had been dropped sometime between 16,570 and 17,000 years ago—toward the tail end of the Ice Age.

“I was very happy when I discovered how old this DNA was,” study author Romina Petrigh of Argentina’s National Council of Scientific and Technical Research said in a statement. “It’s difficult to recover DNA of such an old age as it usually suffers damage over time.” Petrigh attributes the sample’s pristine preservation to the region’s cool, arid climate and salty soils, which rapidly dehydrated the poo and its precious genetic cargo and minimized their breakdown.

Initial analysis of the turd’s size and shape hinted that it had been produced by a large animal from the cat or dog family—a theory the team managed to confirm after extracting the feces’ mitochondrial DNA. The genetic evidence pointed to a puma (Puma concolor), a creature that still roams the region today.

Embedded in the poop were also 64 small parasite eggs that also contained readable mitochondrial DNA, identifying them as the reproductive units of Toxascaris. According to Petrigh, that’s a lot of eggs—enough to underscore just how successful this roundworm was, even millennia into the past.

It’s not clear how the puma contracted its infection, but it was probably via one of two routes: when the feline gobbled up an infected rodent, or swallowed another animal’s egg-laden dung. If it was the latter, though, it’s highly unlikely that poop-producing creature was a domesticated companion of people. The oldest known site of human habitation in Argentina is just 11,000 years old (though, notably, Monte Verde in nearby Chile may have been occupied as early as 18,500 years ago, and the timeline of human migration into the Americas is constantly changing).

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A Toxascaris leonina egg (left, scale bar 20 micrometers) and the puma feces (right, scale bar 20 millimeters) from the study. Image Credit: Petrigh et al. Parasitology, 2019

Even if humans were in close proximity to these pumas 17,000 years ago, the timelines of dog and cat domestication are hazy, and, at least in the Americas, likely postdate the deposition of this particular sample of poop.

Still, the time capsule contained within this turd remains “remarkable,” Piers Mitchell, a parasitologist at the University of Cambridge who was not involved in the study, told Nicola Davis at The Guardian. The study is proof of concept that certain environments are capable of preserving feces, as well as evidence of infectious pathogens within, for many thousands of years, he said. “This will make it easier to plot how different types of parasites are evolving over time.”


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