Ancient poop traces may finally reveal the exact route taken by Carthaginian general Hannibal, as he crossed the Alps to attack ancient Rome in 218 BCE. The evidence, revealed this week in a study published in the Archaeometry journal, could put to rest a centuries-long dispute among historians and shed light on Hannibal’s famous invasion that involved marching an estimated 30,000 troops, 15,000 horses, and 37 elephants, the BBC reports.

Hannibal remains one of history’s most extraordinary commanders and one of Rome’s most committed enemies. The invasion he led over the Alps across today’s French-Italian border caught the Romans by surprise and led to their demise. But ultimately, Hannibal was defeated during the Second Punic War between Carthage and Rome (218-201 BCE). Carthage, which is located in present-day Tunis, was competing with Rome for control over the Mediterranean.

Historians have disagreed for centuries over the exact route Hannibal and his troops took to reach Italy in 218 BCE. Some thought he must have crossed in the north, past present-day Grenoble, The Guardian reports. In the 1950s and ‘60s, British biologist Sir Gavin de Beer advocated for a southern route, saying that Hannibal’s army reached Italy across the Col de la Traversette, a mountain pass that’s 3,000 meters above sea level.

The study seems to confirm this theory. At the Col de la Traversette, researchers found a churned-up layer of sediment that dates to the time of Hannibal’s invasion. Evidence in the soil shows that the layer of sediment was produced by "the constant movement of thousands of animals and humans," Dr. Chris Allen of Queen’s University Belfast, who co-authored the study, told the BBC. Researchers also found evidence of Clostridia bacteria, which make up more than 70 percent of microbes in horse manure and can survive for thousands of years.

The findings aren’t definitive proof that Hannibal and his throng of troops and animals crossed the Alps at the Col de la Traversette, but it’s a good starting point. The researchers will be looking next for a distinctive elephant tapeworm egg in the sediment and for artifacts soldiers must have left behind. Finding this kind of evidence would be final proof that Hannibal used this route.