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Two male lions became infamous for terrorizing and eating humans in 1898 during the construction of a railway bridge over the Tsavo River in Kenya. Now, an innovative genetic analysis of hairs stuck in the sockets of their broken teeth has revealed new insights into the prey the so-called Tsavo man-eaters once hunted.
The harrowing true story of the lions, who invaded tents in the camp at night and dragged victims into the undergrowth, has inspired films and books over the years - and extensive research to understand what drove them to hunt humans .
The lions killed at least 28 people, including those working on the Kenya-Uganda Railway, beginning in April 1898 before civil engineer Lt. Col. John Henry Patterson shot the enormous cats. Patterson then sold the lions' remains in 1925 to Chicago's Field Museum of Natural History, where they have remained ever since.
Thomas Gnoske, collections manager at the museum, first saw thousands of hairs stuck in the lions' teeth when he examined their skulls in the 1990s.
Now, Gnoske and his colleagues in Kenya, from the Field Museum and the University of Illinois Urbana-Champaign, have been able to isolate individual hairs and clumps of hair compressed in the dental cavities and extract DNA from them to identify the animals. identify what they belonged to. . The lion duo ranged further than previously thought in their hunt for food, the findings suggested.
The research was published on Friday in the journal Current Biology. The team also said the method could reveal links between living predators and their prey, as well as in specimens dating back hundreds of thousands of years.
"A key part of this research was creating a method to extract and analyze DNA from individual hairs of prey species found in the teeth of historic museum specimens," said lead study author Alida de Flamingh, postdoctoral researcher at the University of Illinois Urbana. -Champaign, in a statement. "Our analysis showed that historic Tsavo lions hunted giraffes, humans, oryx, waterbuck, wildebeest and zebra, and we also identified hairs that came from lions. This method has many uses and we hope other researchers will apply it to study prey DNA from the skulls and teeth of other animals.
Meet the man-eaters
Gnoske and his colleague and co-author Julian Kerbis Peterhans, associate curator at the Field Museum and professor of natural sciences at Roosevelt University, have been studying lion skulls for decades.
Gnoske discovered that both lions were adult males, although both lacked the distinctive manes associated with adult males. A lack of mane in adult male lions is common and can occur based on the environment and climate the animals live in, injuries that occur as their manes develop and other factors, he said.
Gnoske and Kerbis Peterhans also first reported on the damaged condition of the lion's teeth in 2001, which may have played a partial role in why the animals shifted their focus to attacking and eating humans. One of the lions may have been damaged by a kick or blow from a buffalo or zebra, which, according to their research, could no longer efficiently hunt normal prey.
"We cannot claim that any single cause can guarantee that a lion will turn into a 'man-eater,' but it is clear that a variety of causes will increase the likelihood," they wrote in the January 2001 study, which included a landscape with few prey. or predators that already have a taste for humans after scavenging corpses.
The lions had numerous injuries to their teeth, including partially broken canines, which allowed layers of hair from their prey to build up over time.
For the new research, Gnoske and Kerbis Peterhans carefully removed some of the hairs. The team focused on four small individual hairs and three hair clumps, all of which were more than 100 years old.
Study co-authors Ogeto Mwebi, a senior researcher at the National Museums of Kenya, and Nduhiu Gitahi, a researcher at the University of Nairobi, performed a microscopic analysis of the hairs. De Flamingh then led a genomic study of the hairs with co-author Ripan S. Malhi, professor of anthropology at the University of Illinois Urbana-Champaign.
The combined efforts yielded a wealth of data on the lions' prey and on the predators themselves.
The genetic analysis focused on mitochondrial DNA, or mtDNA, which is inherited from the mother in humans and animals and can be used to trace matrilineal lines of descent. Hair stores mtDNA well and protects it from contamination, De Flamingh said, and mtDNA is also more abundant in cells than other types of DNA.
"We were even able to extract DNA from fragments that were shorter than the nail of your little finger," De Flamingh said.
Hair from the lions shows they shared the same maternally inherited mitochondrial genome, supporting previous beliefs that the two males were siblings. And lion hair stuck between their teeth suggests the brothers were closely bonded and cared for each other, Kerbis Peterhans said.
Tracking down links to prey
The researchers discovered several surprises when they analyzed the hair of the prey the lions ate.
The discovery of wildebeest DNA was unexpected because the nearest population of the animals was at least 80.5 kilometers away in the 1890s - although the lion brothers left Tsavo for about six months before returning to attack the camp again in November 1898 .
"It suggests that the Tsavo lions may have traveled further than previously thought, or that wildebeest were present in the Tsavo region at that time," says de Flamingh.
Using microscopy, a single buffalo hair was also found, and although buffalo are the favored prey of modern Tsavo lions, the viral disease rinderpest devastated cattle and buffalo populations in the Tsavo region in the late 19th century. The highly contagious disease has virtually wiped out livestock and their wild relatives, including the Cape buffalo, Kerbis Peterhans said.
"Patterson kept a handwritten diary during his time at Tsavo," says Kerbis Peterhans. "But he never mentioned in his diary that he saw buffalo or native cattle."
In the meantime, the researchers are being careful and respectful with the human hair uncovered during their study, which they declined to describe or analyze to predict ancestry or ethnicity.
"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," the authors wrote in the study. "The anthropological methods require discussions with local institutions and groups about the project and reporting the detailed human colonial history of this geographic region, which is beyond the scope of this current study."
The team has a plan to work with the local community to see how they want to continue studying human hair and tracing their genetics, Malhi said.
Reconstructing a predator's timeline
The genetic technique developed during the research could be used to study the contents of broken teeth from ancient carnivores, opening a new way to piece together the past, Malhi said.
Love Dalén, professor of evolutionary genomics at Stockholm University, considers the technique "quite ingenious."
"We have known for some time that it is possible to obtain nutritional information by extracting DNA from plaque in old teeth," says Dalén, who was not involved in this study. "But no one has thought of using hairs in the teeth of carnivores as a source of DNA instead."
Microscopy work is underway to identify more individual hairs in the lions' teeth.
"At least in the published literature, I don't know if there have ever been individual lions in history where such a diverse and long list of prey species has been documented," Gnoske said.
Future analysis of the hair layers will allow the team to reconstruct a partial timeline of the lions' diet and determine when they began hunting humans.
"Layers in the lower parts of the tooth cavity represent prey eaten earlier in life, and layers at the top of the tooth cavity are from recently eaten prey," De Flamingh said. "This type of analysis can provide insight into the human-lion conflict that continues to affect many communities in the region and in Africa in general. For example, if lions start out hunting wild animals, but then move on to attack pets and eventually target humans, we can develop strategies and recommendations to reduce these risks."
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