Hannibal crosses the Alps on an elephant. (Nicolas Poussin)

More than 2,200 years ago, Hannibal led the Carthaginian army — which included 37 elephants — over the Alps into Italy. Although Hannibal's rampage against the Roman Empire was eventually countered, the crossing of the Alps remains a bold and historic military move. Historians agree that the brutal crossing was a stroke of strategic genius, but they have never been able to agree on the exact route that Hannibal, his men and his elephants took across the snowy peaks.

Poop science to the rescue!

In a study published Monday in the journal Archaeometry, researchers argue that new evidence in the form of some very old poop might hold the key to solving this mystery once and for all.

They say that microbial evidence suggests a "mass animal deposition" (a.k.a. poop) occurred in the Col de Traversette pass in 218 B.C. — just when Hannibal was making his journey to Rome. By digging around in a peaty bog along the pass, the researchers found what they think are microbes usually associated with horse manure.

"Over 70% of the microbes in horse dung are from a group known as Clostridia and we found these microbes in very high numbers in the bed of excrement," study author  of Queens University wrote in an article for the Conversation. "Much lower levels of Clostridia genes were found elsewhere at the site. We knew it was these bugs because we were able to partially sequence genes specific to these organisms. The bacteria are very stable in soil, surviving for thousands of years."

There was another clue as well: Allen and his colleagues believe they see geological evidence of those horses trudging through the muck. The layer of bog where they found their poopy microbes showed evidence of having been kicked up and then compacted again, which isn't something they saw elsewhere.

They also found signs of horse tapeworms. “There is even the possibility of finding an elephant tapeworm egg,” Allen told Britain's Guardian newspaper. “This would really be the pot of gold at the end of the rainbow.” Horses trudging through the Alps are suspicious, but solid evidence of elephants in their company might close this case for good. Until then, Allen and his colleagues will have to keep probing the poop and surrounding areas for more clues.

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