Louis François Fernand Hector de Loys, (1892-1935) was a Swiss geologist and pioneer of oil field prospection in Europe, Africa and America. Unfortunately de Loys is today less known for his geological work than for a story involving a strange photography.

In 1920 a bunch of exhausted men reached the bank of the Tarra River, a tributary of the Rio Catatumbo, located in the borderlands of Venezuela and Colombia. They were the only survivors of the "Colon Development" - expedition, disappeared in 1917 in the mountains of the Sierra de Perijeé during geological fieldwork. The region was a dangerous jungle infested with tropical beasts of prey, parasites and diseases, inhabited only by the hostile Motilones Indians. They found no oil, but had a strange encounter with an unknown creature.

One day de Loys spotted along the shores of the Rio Tarra two large monkeys covered with reddish fur and lacking a tail. More strangely the two animals walked upright and approached slowly the expedition, visibly irritated, shouting, brandishing the arms and using they own excrements as projectiles against the frightened men. The men decided to respond to the attack and shoot in direction of the two apes, killing the female.

Since de Loys had never seen such large monkeys, he took various photos of the body and tried to preserve the skull. However the bones soon started to decay and during a trip on the river the boat capsized and most of the photos of the ape got lost.

When de Loys finally returned home he hid the only surviving photography in his private notebook. Only years later a friend, the Swiss anthropologist George Alexis Montandon (1879-1944), accidentally rediscovered this photo.

The animal in the photography showed characteristics that are not found in the monkeys of the new world, like the upright posture, the absence of a tail, but especially the extraordinary size. Montandon was fascinated by the possibility of a great ape or even primitive man still surviving in South America. Already early explorers reported strange encounters in the jungle:

"It is, however, possible that a great anthropoid ape may exist, as yet unrecognised by zoologists. On the cataracts of the upper Orinoco, Humboldt heard reports of a "hairy man of the woods", which was reputed to build huts, to carry off women, and to devour human flesh [...] Both Indians and missionaries firmly believe in the existence of this dreaded creature, which they call vasitri, or "the great devil." Humboldt suggests that the original of what he boldly calls "the fable", may exist in the person of "one of those large bears, the footsteps of which resemble those of man, and which are believed in every country to attack women;" and he seems to claim credit for being the only person to doubt the existence of the great anthropomorphous monkey of America. But it might be permitted, in return, to ask what "large bear" is known to inhabit Venezuela; and whether it is true that bears´ footsteps have a signal resemblance to those of men; and that bears specially attack women."

GOSSE, P.H. (1861): "The Romance of Natural History."

However the scientific description of the species "Ameranthropoides loysi" - de Loys' American human-like ape - by Montandon was accepted only by the French establishment and rejected by scientists from Great Britain and North America. The eminent English naturalist Sir Arthur Keith stated that the photo showed only a species of spider monkey - Ateles belzebuth native in the explored region- with the tail deliberately cut off or hidden in the photography.

In fact spider monkeys are typical apes found in South America; however the largest known extant species reach 110cm (3,5 feet) height standing on their hind limbs, De Loys ape was with the estimated 157cm (5 feet) height considerable larger. The only known fragmentary remains of such a large spider monkey species are those of Protopithecus brasiliensis, the "primitive monkey of Brazil", an extinct ape discovered by the Danish naturalist Peter W. Lund in 1838 in the Brazilian region of Bahia.

Unfortunately the size of the animal can not be compared to other objects apart a strange box on which the corpse was posed - many published versions of the photography were also modified or the image itself has been cropped, magnifying the impression left by the ape. De Loys himself was very reluctant to promote the story behind the photo. In the official report of the expedition published in 1929 there is no mention of the creature or subsequent research and de Loys mention it only, forced by Montandon, in a sensationalistic article entitled "Found at Last - The First American" published in the Illustrated London News.

Fig.2. The photography of de Loys´ ape - "Ameranthropoides loysi", from MONTANDON 1929 (image in public domain).

In 1998 historians Pierre Centlivres and Isabelle Girod published an article suggesting that the entire story was an idea of anthropologist Montandon.

Montandon was strongly influenced by racist hypothesis of human evolution popular at the time; he proposed a polyphyletic origin of humans and considered the various human races descending from local monkey species. He affirmed that Africans evolved from gorillas and Asians from orang-utans. A missing link - as the supposed Ameranthropoides - was a perfect example of an evolutionary line between spider monkeys and South American Indians and would have confirmed his racist view of human evolution.

The most plausible hypothesis that emerges now is a manipulated photo of a common spider monkey of the species Ateles belzebuth, used by Montandon to promote his hypothesis of human evolution. This approach is supported by a detail in the complete view of the photo - there are stumps of non-native, cultivated Banana Trees visible - impossible if the encounter happened really in the middle of the unexplored jungle.

Finally in 1999 the July-August edition of the Venezuelan scientific magazine "Interciencia" published a letter send in 1962 from Doctor Enrique Tejera to the editor Guillermo José Schael of the magazine "Diario El Universal":

"[...] This monkey is a myth. I will tell you his story. [...]

Mister Montandon said that the monkey had no tail. That is for sure, but he forgot to mention something, it has no tail because it was cut off. I can assure you this, gentlemen, because I saw the amputation…[].

Who is speaking here in 1917 was working in a camp for oil exploration in the region of Perijá. The geologist was François de Loys, the engineer Dr. Martín Tovar Lange. De Loys was a prankster and often we laughed at his jokes. One day they gave him a monkey with an ill tail, so it was amputated. Since then de Loys called him "el hombre mono" (the monkey man).

Some time later I and Loys went in another region of Venezuela: in an area called Mene Grande. He always walked along the side of his monkey, who died some time later. De Loys decided to take a photo and I believe that Mr. Montandon will not deny it is the same photograph that he presented today. [in 1929 Montandon presented the Ameranthropoides in a public lecture].

More recently during a visit to Paris my astonishment was great visiting the Museum of Man. On top of a monumental scale, filling the back wall, there was a huge photo with the caption: "The first anthropoid ape discovered in America."

It was the photograph of de Loys, beautifully modified. The plants were no longer visible in the background, and it was not possible to understand on which kind of box the monkey was sitting. The trick is done so well that within a few years the monkey will be over two meters high [...].

Finally, I must warn you: Montandon was not a good person. After the war he was executed because he betrayed France, his homeland.

Sincerely, Your friend Enrique Tejera."

If the myth of a large ape-like creature in South America has a zoological explanation (like a still undescribed monkey species), the photo of de Loys surely has nothing to do with it.

Despite his role in the prank (he contributed the photo and the story and later never resolved the case), de Loys continued his promising career in the field of exploration geology. In 1926 he engaged in the Turkish Petroleum Company, cultivating contacts with geologists and scientists all over the globe. In 1928 he became a fellow of the Geological Society of London and soon visited the Irak to study the geology and the possible oil reserves of the region. Here he encountered Syphilis, returned to the town of Lausanne in France where he died still too young, October 16, 1935.


DUNNING, B. (20.03.2012): De Loys' Ape. Skeptoid Pocast #302

CENTLIVRES, P. & GIROD, I. (1998): George Montandon et le grand singe américain. L'invention de l'Ameranthropoides loysi. Gradhiva 24: 33-43

HEUVELMANS, B. (1995): On the Track of Unknown Animals. Kegan Paul International, London: 677

MONTANDON, G. (1929) : Découverte d'un singe d'apparence anthropoïde en Amérique du Sud. Journal de la Société des Américanistes de Paris, 21 (6): 183-195

ROSSI, L. (2012): Criptozoologia - Animali misteriosi tra Scienza e Leggenda. Photocity Edizioni Open: 300

SHERMER, M. (2002): The Skeptic Encyclopedia of Pseudoscience. ABC-CLIO: 903

VILORIA, A.L.; URBANI, F. & URBANI, B. (1998): François de Loys (1892-1935) y un hallazgo desdenado: La historia de una controversia antropologica. Intercienca Mar.-Apr. Vol.32(2): 94-100

VILORIA, A.L.; URBANI, F.; McCOOK S. & URBANI B. (1999) : De Lausanne aux forêts vénézuéliennes. Mission géologique de François de Loys (1892-1935) et les origines d'une controverse anthropologique. Bulletin de la Société Vaudoise des Sciences Naturelles, 86 (3): 157-174