Human DNA found in lion teeth confirms a tragic legend from history

Given half a chance, lions are not averse to chewing occasionally Homo sapien that could enter their territory unattended. Fortunately, few African big cats have ever made the habit of actively seeking out humans to eat.

There are of course exceptions. One of the most infamous events occurred in Kenya’s Tsavo region in 1898, when two male lions spent months terrorizing workers building a railway bridge over the Tsavo River.

The ancient teeth of these lions – long mythologized as ‘man-eaters’ – are now revealing new secrets, not just whether they ate humans, but clues as to why.

Using recent advances in techniques for sequencing and analyzing ancient and degraded DNA, researchers from the US and Kenya have investigated animal hairs stuck in lions’ teeth.

They report their findings in a new study, including specific animals the lions ate.

Such insights can help us not only check the facts about the episode, but also better understand what could drive wild predators to behave so unusually.

The first reports of lion attacks began in March 1898, shortly after the arrival of Lieutenant Colonel John Henry Patterson, a British army officer and engineer who oversaw the project to connect the interior of Kenya and Uganda with a railway.

The British had recruited thousands of workers to build the bridge, mostly from India, and housed them in camps that stretched several miles, Patterson wrote.

Patterson initially doubted reports of two workers abducted by lions, but was convinced weeks later when Ungan Singh, an Indian military officer accompanying him, suffered the same fate.

Patterson spent that night in a tree and promised to shoot the lion when he returned. He heard “ominous roaring,” he wrote, and then a long silence, followed by “a great uproar and frenzied shouts from another camp about half a mile away.”

The next morning he heard that a lion had attacked another part of the camp.

Thus began a lengthy campaign by Patterson and others to kill the perpetrators: two large, manless male lions. Maleless males are more common in some regions, including Tsavo, possibly due to the local climate or vegetation.

The attacks once stopped abruptly for a few months, Patterson notes, although “we heard from time to time of their depredations in other neighborhoods.”

When the lions finally returned, they seemed even bolder: instead of attacking individually as before, they often entered camps together.

Patterson ultimately killed both lions in December.

The final death toll of the lions remains unclear; some estimates are as high as 135, although a 2001 study suggests the numbers were probably closer to 30 – a figure that, while much smaller, is by no means insignificant.

Patterson preserved the lions’ remains and eventually sold them to the Field Museum of Natural History in Chicago in 1925.

Decades later, when ecologist Thomas Gnoske, the museum’s collections manager, found the lions’ skulls in storage, he noticed hair fragments lodged in exposed dental cavities.

Some scientists speculate that the lions hunted humans precisely because of damaged teeth, which could have made it difficult to subdue larger prey.

In any case, the damage appears to have preserved clues about the lions’ diet. Gnoske and colleagues have now conducted an in-depth study of the hairs, including microscopic and genomic analyses.

First they had to confirm the age of the hairs, explains co-author Alida de Flamingh, a conservation biologist at the University of Illinois Urbana-Champaign.

“We look at whether the DNA has these patterns that typically occur in ancient DNA,” says de Flamingh.

Once the samples were verified, the authors focused on mitochondrial DNA (mtDNA). It is more abundant in cells than nuclear DNA, and hair can also preserve mtDNA and limit contamination, which helps in older samples.

‘And because the mitochondrial genome is much smaller than the nuclear genome, it is easier to reconstruct in potential prey species,’ adds de Flamingh.

The hairs were not in good condition, but they still yielded usable mtDNA. Some of the hair came from the lions themselves.

The rest came largely from an unsurprising mix of local ungulates – with one notable exception. The teeth of these infamous man-eaters do indeed contain human hair.

“Analysis of hair DNA identified giraffes, humans, oryx, waterbuck, wildebeest and zebra as prey, and also identified hairs derived from lions,” write de Flamingh, Gnoske and team.

The lions’ mtDNA suggests they were brothers, as suspected. According to the analysis, they had eaten at least two giraffes and a local zebra.

The team also created a database of mtDNA profiles for potential prey species that occupied the lions’ habitat in 1898.

Finding mtDNA from the wildebeest was strange, they note, since the nearest wildebeest at the time lived about 50 miles away. But when Patterson reported a prolonged lull in attacks, the lions may have been hunting wildebeest.

It was also remarkable to find only one buffalo hair, the authors added, and no buffalo mtDNA. “We know from what the lions in Tsavo eat these days that buffalos are the favorite prey,” says de Flamingh.

That could indicate why these lions hunted humans.

“Patterson kept a handwritten field diary during his time at Tsavo,” says paleoanthropologist Julian Kerbis Peterhans of Roosevelt University and the Field Museum. “But he never mentioned in his diary that he saw buffalo or native cattle.”

Runderpest, a viral disease of ungulates, had been introduced into Africa from India years earlier. It destroyed buffalo and cattle across the region in the 1890s, possibly forcing some lions to find new prey.

For this study, the researchers chose not to conduct further analysis of the human hairs to identify potential victims.

“There may still be descendants in the region today, and to practice responsible and ethical science, we use community-based methods to expand the human aspects of the larger project,” they write.

The research was published in Current biology.

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