When looking for a scientific explanation to the Tsavo lion attacks, some questioned whether the unique man-eater group was actually a different species of big cat that lived during the Pleistocene epoch. It was known that the males lack signature manes and often grow larger than average lions.

Another theory attributed the Tsavo lions’ aggression to elevated levels of testosterone. But so far, these theories have come up empty. The Tsavo lion’s maneless state is likely an adaption to the hotter weather since fuller, darker manes usually correlate to cooler, wetter climates. This makes sense since the Tsavo region receives little rainfall and high average temperatures.

As for their relative size, the lions in this area are not abnormally large when taken as a whole and research has not confirmed the possibility of increased testosterone either. So where does the attraction to humans as prey come from in the so-called ‘man-eaters of Africa’ and the other groups of lions that have ravaged human settlements in modern times?

Instead of biological instinct, experts often pinpoint external conditions that influence this predatory behaviour. Overall, the population of lions in Africa is on the decline, hovering somewhere between 16,000 and 47,000 as of 2006. According to the Kenya Wildlife Service, Kenya is losing an average of 100 of its 2,000 lions annually due to growing human settlements, increasing farming, climate change and disease.

Human population has consistently been on the rise – along with lion attacks. Tanzania in particular has experienced a harsh upswing in lion confrontations, with at least 563 related deaths since 1990. Lions will assault humans for a number of reasons.

Altered habitats is a big reason known to impact wildlife in general. In case of the lions, this puts them in a pinch for feeding themselves. When that happens, lions must sometimes practice prey switching, or changing up their diets to accommodate for the loss of usual food sources.

This temporary change happens naturally throughout lions’ lives because of the migration patterns of their prey. However, when that usual prey runs out, the lions may switch to another food source, like humans.

In the 1898 railroad episode for instance, much of the larger wildlife such as buffalo and zebra herds had been decimated due to an infestation of Rinderpest disease. That eliminated a chunk of the Tsavo lions’ food sources.

When the railroad project moved into the region, so did piles of bodies of workers who died from exhaustion or poor working conditions. These bodies were not properly buried, probably attracting lions to the easy meal that made up for the lack of game.

After acquiring the taste for human flesh, and without additional prey, the lions began going after live humans. Many times, humans may serve as easier dinners to acquire than other wildlife.

Age or injuries is another prime reason for a lion to turn a man-eater. Old or injured lions may capitalise on the ability to sneak up on people and dine on softer flesh compared to the hard and tough animal flesh they would normally chew through.

In 2004, for example, a man-eater lion was responsible for slaughtering 49 people over the course of 20 months in Tanzania. An autopsy on the big cat revealed a severe abscess in one of its teeth, which experts attribute to why it began feeding off of people.

Another intriguing facet of the man-eating habit is the potential for lions to pass it down to their cubs! One study of the Tsavo lions by scientists at Chicago’s Field Museum discovered that generations of the same pride exhibited similar human-eating tendencies!

Today, lions have less space to roam because farmers have converted land into arable plots. Along with agriculture, people also raise livestock, which lions will target, drawing them closer to homes.

This type of development has also negatively impacted the amount of available prey for lions, building up to the perfect storm in eastern African countries like Ethiopia, Tanzania and Mozambique. While it is not a natural practice, survival instincts can set in, and lions can easily become man-eaters out of necessity.

A man-eater can therefore emerge out of the necessity to survive, due to age, injuries or inheritance of similar dietary traits from past generations. Whether being maneless and significantly larger than its counterparts is part of this, is still debatable though.