On the trail of Hannibal's army - and elephants - in the Alps

by Mary Caperton Morton
Wednesday, July 6, 2016

In the third century B.C., during the Second Punic War between the Romans and Carthaginians, Carthaginian general Hannibal led a massive army over the Alps to invade Italy from the supposedly impenetrable north. It is one of the most famously brazen moves in military history, but the exact route that Hannibal’s army — which included tens of thousands of foot soldiers and cavalrymen, thousands of horses and nearly 40 elephants — took through the mountains has long been a mystery. Now, a team has found microbial evidence that a large number of horses crossed the Alps from France into Italy over the 3,000-meter Col de la Traversette pass around 218 B.C. But not everybody is convinced that the Traversette pass route matches detailed historical accounts of Hannibal’s journey.

“Hannibal knew exactly what he was doing and where he was going. We’re trying to put the pieces together to figure out how on Earth he did it,” says Bill Mahaney, a geomorphologist at York University in Toronto, Ontario, and lead author of the new study published in Archaeometry.

Over the years, as many as 10 different routes have been proposed for Hannibal’s trek over the Alps, but little to no confirmed archaeological evidence has been uncovered along any of the 2,200-year-old routes. Instead, most of the geographical clues have been gleaned from the historical accounts written by the Roman writer Polybius, who interviewed surviving soldiers soon after their epic march, noting geographical features such as a two-tiered rockfall, a large encampment at or near the summit and a clear view from the summit down onto Italy’s Po River Plain.

In 2004, Mahaney surveyed the passes proposed by the different routes and found a large rockfall caused by two separate accumulations of rubble, one deposit on top of the other, below the summit of the Col de la Traversette, on the border of France and Italy. “No such deposit is found below any of the other passes on the lee side of the Alps,” he says. Then his team turned their attention to a peaty bog at 2,600 meters, just below the Traversette pass, where the army could have camped before descending into Italy. The team cored the bog and found mostly mud, except for a layer about 40 centimeters deep that appears to be more disturbed, churned and compacted than the rest of the core.

“This layer is very unusual, but it makes sense if you think about how an army of boots and hooves and even elephant feet might impact the ground,” he says. Further testing of the layer, including microbial, geochemical, pedological and pollen analyses, confirmed that horses were present. “We even found a tapeworm egg that’s only found in horses,” Mahaney says. Carbon-14 dating of the layer gave an age estimate of 218 B.C., which matches the timeline of Hannibal’s crossing.

But the evidence isn’t a slam dunk, says Patrick Hunt, a historian at Stanford University who was not involved in the new study. “Polybius gives us lots of criteria from which we can try to extrapolate Hannibal’s route,” Hunt says. “However, with all due respect for [Mahaney’s team’s] excellent scientific approach, the Traversette route doesn’t fit Polybius' descriptions.”

For example, he says, Polybius wrote that the army camped at the summit and Hannibal showed his men the route down into Italy the next morning from the summit. “But the Traversette has no [area that could accommodate a] summit encampment. It’s essentially a knife-edge up there. The camp [Mahaney] proposes is more than 300 meters below the summit.” Furthermore, Mahaney’s team focused on Traversette because of a two-tiered rockfall, as described by Polybius, but Hunt says such rockfalls are common throughout the Alps and found at several other potential crossings, including the more northern Clapier-Savine Coche route favored by his team, also on the border of France and Italy.

Mahaney disagrees that the Clapier-Savine Coche is a more worthy candidate. “An army of nuns could walk right down off that pass into Italy,” whereas Hannibal’s army’s descent was famously steep and dangerous, with many men and animals lost to falls on the way down into Italy. “Polybius does say Hannibal camped on the summit but in fact none of these passes have open areas where one might camp, not even the Clapier,” Mahaney says.

The battery of tests that Mahaney’s team performed on the core samples is “impressive,” Hunt says, but none of the evidence is identifiable uniquely to Hannibal’s army. Horses have been an important means of transportation in the Alps for thousands of years, and age dating has wide error margins, he adds. “When they find elephant dung,” Hunt says, “I’ll be more persuaded they have the right route.”

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