DNA reveals the past of man-eating African lions

The Tsavo Man-Eaters were a pair of large man-eating male lions in the Tsavo region of Kenya, which were responsible for the deaths of many construction workers on the Kenya-Uganda Railway in the late 1890s. The lion pair was said to have killed dozens of people. While the terrors of man-eating lions were not new in the British public perception, the Tsavo Man-Eaters became one of the most notorious instances of dangers posed to Indian and native African workers on that Uganda Railway. They were eventually killed by the British Officer Lieutenant-Colonel John Henry Patterson, and their skulls, and skins, now sit in a museum in Chicago. Recently, researchers in the city have isolated and sequenced DNA from hairs of the lions’ victims lodged inside the animals’ teeth; Alida de Flamingh at the University of Illinois Urbana-Champaign has been telling me what they found…

Alidade - There were these two lions in Tsavo, it's a region in Kenya, and they're interesting because they've been the topic of many movies and books. Most famously they're known for having also preyed on humans. And so those are the two lions that we study in this specific research and they're currently at the Field Museum in Chicago.

Chris - Are they, what, taxidermy specimens? Are they just skeletons? What's there in the museum to see?

Alidade - So at the moment in the museum, there are actually the two stuffed or rearticulated lions, skins on the one side, and their skulls are actually separate from them. So you can see both the skulls but also the lion's skins that have been stuffed, which is great because that means we had access to the skulls without having to damage any of the skins or actual rearticulated lions.

Chris - So confronted with these two lion remains, how did you then progress this? What did you actually test and what question were you asking?

Alidade - So we wanted to see if we can identify the prey from the hairs that were compacted in tooth cavities from these two lion skulls, so from their lower jaws. To do this, we used both microscopy, but we also looked at genetic material that was contained in hair fragments that were in these tooth cavities.

Chris - So are you saying, when the lions chowed down - for want of a better phrase - on whatever they were preying, on bits of the hair were ending up embedded in the teeth, and because they don't have toothbrushes, that stuff just stays in there?

Alidade - That's exactly what happened, right! We don't know exactly how old they were when this happened, but both of them had parts of their lower canines broken off and this created a cavity or a hole in which hair was compacted as these lions were eating. So the hair would get stuck in there and would kind of compact up.

Chris - And what's the preservation of the material like? Can you get meaningful amounts of, I presume you're going for DNA, from the hair that's in that cavity?

Alidade - Yes, and this is one of the interesting things is a lot of people are aware that to get a really large quantity of DNA, if you've watched any type of CSI show, right, they usually want to have the follicle of the hair shaft of your hair present. But in this case, because we are focusing in on a specific type of DNA that's called mitochondrial DNA, it's a type of DNA that's really well preserved in hairs without follicles. And so that's why we targeted this type of genetic material.

Chris - So what you just grind up the hair and out comes the DNA? you can separate that off?

Alidade - It's a little bit of a complicated situation where we have to work in a really, specialised laboratory, and that's at the University of Illinois, where there's absolutely no external DNA or DNA other than the ones that you're interested in present. And so we take those hairs and we actually dissolve them in a combination of different chemicals and that breaks open the cells and releases the DNA. And that's what we use to start out this process of DNA analysis.

Chris - And then you read the DNA sequence which, presumably, because the mitochondrial DNA of different species is very different, you can begin to pinpoint what sorts of things these animals had been eating?

Alidade - Exactly, so each individual species has a unique type or sequence of mitochondrial DNA. And so you can use this to identify the different types of prey that these lions were eating.

Chris - How do you know, though, that someone didn't contaminate the skull, the tooth, the environment that they were in, and that's what you are picking up? How do you know this genuinely was prey?

Alidade - There's multiple lines of evidence that point towards the accuracy of our data. The number one is that we've never analysed anything like wildebeest or zebra or giraffe in this specialised facility that's at the University of Illinois. The second is, when we did this analysis, the type of mitochondrial DNA that we got when we compared it, for example, for the giraffe or zebra to known mitochondrial DNA from across Africa, we find that the lions, the hair DNA, matches most closely with other giraffe or zebra that were actually from Kenya and not from the rest of Africa. So that's a good support or validation that the DNA that we're extracting is actually authentically from animals that used to live in Tsavo.

Chris - What about the human remains? Could that be mapped to Kenya? Were the locals being picked on or was it colonists coming in and and being picked off?

Alidade - Yeah, so we are refraining to infer to any type of ethnic identity from this really small piece of DNA that we analysed. We do however know that this DNA that we got from the hair had specific damage patterns. So your DNA degrades over time and it had damaged patterns that are characteristic of what you would expect from ancient DNA or DNA that's really old and have degraded over time.

Chris - We've known that we could do this for mitochondrial DNA in related ways for some time. What is new about this study and what does it add?

Alidade - So I would say two things. First is, methodologically, this is interesting because where folks have used ancient hairs to do any type of research, usually you know what type of animal you are actually sequencing or getting DNA from. A good example is, people have analysed hair from Siberian mammoths. In our case, we didn't know what the hairs were from. And so we took a backwards approach and said, we have a bunch of DNA, can we identify the actual animals that they're from? So that's a type of novel way of interpreting palingenetic data or ancient DNA data from animals or from hairs. The other kind of interesting aspect of this project is, it also gives us kind of insights into the historical ecology or interactions that these lions had with their environments. For example, the presence of wildebeest in the area, which is, until we did the study, folks hadn't reported wildebeest at least from that specific area in Tsavo. So it does give us some insights that we didn't have before.