20th century^[5]

The first report of the mokele-mbembe comes from German Captain Ludwig Freiherr von Stein zu Lausnitz, as described by Willy Ley in the book The Lungfish and the Unicorn (1941). Von Stein was ordered to conduct a survey of German colonies in what is now Cameroon in 1913. He heard stories of an enormous reptile called "Mokele-mbembe" alleged to live in the jungles, and included a description in his official report. According to Ley, "von Stein worded his report with utmost caution," knowing it might be seen as unbelievable.^[6] Nonetheless, von Stein thought the tales were credible: trusted native guides had related the tales to him, and the stories were related to him by independent sources, yet featured many of the same details. Though von Stein's report was never formally published, Ley quoted von Stein as writing:

The animal is said to be of a brownish-gray color with a smooth skin, its size is approximately that of an elephant; at least that of a hippopotamus. It is said to have a long and very flexible neck and only one tooth but a very long one; some say it is a horn. A few spoke about a long, muscular tail like that of an alligator. Canoes coming near it are said to be doomed; the animal is said to attack the vessels at once and to kill the crews but without eating the bodies. The creature is said to live in the caves that have been washed out by the river in the clay of its shores at sharp bends. It is said to climb the shores even at daytime in search of food; its diet is said to be entirely vegetable. This feature disagrees with a possible explanation as a myth. The preferred plant was shown to me, it is a kind of liana with large white blossoms, with a milky sap and apple-like fruits. At the Ssombo River I was shown a path said to have been made by this animal in order to get at its food. The path was fresh and there were plants of the described type nearby. But since there were too many tracks of elephants, hippos, and other large mammals it was impossible to make out a particular spoor with any amount of certainty.

However, according to Brian Dunning, in a 1929 German book by science author Wilhelm Bölsche called Dragons: Legend and Science, Bölsche wrote that von Stein clearly believed that the creature described was not an actual animal, but instead was nothing more than local folklore.^[7]

According to German adventurer Lt. Paul Gratz's account from 1911:

The crocodile is found only in very isolated specimens in Lake Bangweulu, except in the mouths of the large rivers at the north. In the swamp lives the nsanga, much feared by the natives, a degenerate saurian which one might well confuse with the crocodile were it not that its skin has no scales and its toes are armed with claws. I did not succeed in shooting a nsanga, but on the island of Mbawala I came by some strips of its skin.^[8]

Tales of entities like mokele-mbembe, living saurians or large scientifically unidentified creatures walking around the African rain forest, are not rare; there have been multiple tales of large, smooth-skinned quadrupeds with long necks that fed on large prey still living in central Africa.^[9] It was only after the description of the mokele-mbembe surfaced that the rest of the world started interpreting those legends as possessing a dinosaur-like body structure. A notable example would be the emela-ntouka, an elephant-sized creature that shares a lot of similarities with the mokele-mbembe. It is described as having smooth skin, a strong and muscular tail, and a "horn" or "tooth".^[10] Another similar creature, the jago-nini, was described by Alfred Aloysius Smith, who had worked for a British trading company in what is now Gabon in the late 1800s, who briefly mentions it in his 1927 memoir.^[11]

Outdated 1897 restoration of a submerged Brontosaurus by Charles R. Knight; depictions like this may have influenced the myth

Reports of entities described to be dinosaur-like in Africa caused a minor sensation in the mass media, and newspapers in Europe and North America carried many articles on the subject in the early 1910s; some took the reports at face value, while others were more skeptical. It is notable that Western Europe and the Americas were going through a pop cultural interest in dinosaurs, of which the Brontosaurus was one of the most popular. This cultural trend could have contributed to both the reports as well as the tendency for newspapers to claim the reported beast was a sauropod.^[12]

Several expeditions, of varying scientific credibility, were undertaken in the 20th Century to search for mokele-mbembe or interview claimed eyewitnesses. In 1980 and again in 1981, explorer Henry Powell and biologist Roy Mackal visited the Congo region and interviewed native residents. They did not find any direct physical evidence, but nonetheless argued consistent statements from claimed eyewitnesses tended to support the creature's existence. Mackal published a book in 1987 detailing his expeditions.^[13] Mackal admitted his investigation was "tinged with some romanticism", but also insisted he had serious scientific intent.^[14] Prothero argues the Powell-Mackall expedition almost single-handedly popularized the modern concept of mokele-mbembe to Westerners, yet was seriously flawed. Mackal's training was in virology, which arguably did not qualify him to search for a large, exotic creature; and Mackal seemed to uncritically accept eyewitness statements without considering the possibility people might lie or exaggerate for financial gain, for attention, or to impress an American visitor. Furthermore, Mackal was dismissive of Africans who "denied knowledge of mokele-mbeme" or who asserted the creature did not exist.^[15] Zoologist Marcellin Agnagna said he took a film of mokele-mbeme in 1983 but the footage did not develop properly. Prospero describes the story as "suspicious", noting critical details of Agnagna's account have changed and none of it was supported by other witnesses. Scottish explorer William "Billy" Gibbons led two expeditions in 1985 and 1992, though Prothero question his motives as a creationist and describes Gibbons as not following even basic scientific principles.^[16] Journalist Rory Nugent's book Drums Along The Congo: On The Trail Of Mokele-Mbembe, the Last Living Dinosaur was published in 1993 by Houghton Mifflin. Nugent's book included a photograph he claimed was possibly mokele-mbembe, but which Prothero argues was more likely a floating log.^[17]

21st century

In 2001, BBC broadcast in the TV series Congo a collective interview with a group of Biaka pygmies, who identified the mokele-mbembe as a rhinoceros while looking at an illustrated manual of wildlife.^[18] Neither species of African rhinoceros is common in the Congo Basin, and the mokele-mbembe may be a mixture of mythology and folk memory from a time when rhinoceroses were found in the area.

In 2016, a travel documentary crew from South Africa made a documentary about searching for mokele-mbembe, which they later sold to Discovery Africa.^[19][20] The team spent roughly four weeks in the Likuoala swamp region visiting various Aka (pygmy) villages, collecting stories of the creature's existence. They pointed out the difficulty of differentiating between a mokele-mbembe's metaphysical and physical existence. While they interviewed people who believed in its presence, others stated it died at least a decade ago.^[21]

In 2018, Lensgreve of Knuthenborg, Adam Christoffer Knuth, along with a film crew from Danish Radio and a DNA scientist, traveled to Lake Tele in Congo, in search of the mokele-mbembe. They did not find the cryptid; however, they found a new species of green algae.^[22][23]