Field of Science

De Loys' Ape

Louis François Fernand Hector de Loys, (1892-1935) was a Swiss geologist pioneer of the young science of oil fields prospecting; he travelled extensively and collected experience in Europe, Africa and America during the golden age of oil exploitation.
Unfortunately de Loys is less known for his geological achievements than for a strange story about a strange photography.

Fig.1. François de Loys (1892-1935), photo taken probably before his expeditions to Venezuela in 1917; however de Loys was only 25 when he visited the country, so the general impression of a young, intrepid geologist, probably also larksome, was still valid at the time of his adventures (VILORIA et al. 1998).

In 1920 a handful of exhausted men reached the bank of the Tarra River, a tributary of the Rio Catatumbo in the borderlands of Venezuela and Colombia. They were all what remained of a group of 20 prospectors of the Netherland oil company "Colon Development", which had ventured in the Sierra de Perijeé, a range of mountains, in 1917. In charge of the expedition, intended to geological map and study the region for a planned exploitation of the suspected oil reserves, was de Loys.
The area was not only a dangerous jungle infested with tropical beasts of prey, parasites and diseases, but also inhabited by the hostile Motilones Indians, they decimated one after another the members of the expedition. It seemed already that the expedition was a failure, but in the last part a strange encounter occurred.

One day de Loys spotted at the shores of the Rio Tarra two large, biped monkeys covered with reddish fur and without tails. The two threatening animals walked upright and begun to approach the expedition, visibly irritate
d, shouting, brandishing with the arms and finally defecating in their own hands and using the excrements as projectiles against the expedition. Finally the frightened men decided to respond to the attack, so they shoot in direction of the two apes and killed was seemed a female, meanwhile the male escaped in the jungle.
Since de Loys and his people had never seen such large monkeys, he tried to preserve the skull and take various photos of the body. However soon the skull begun to decay and during a trip on the river the boat capsized and most of the photos of the animal got lost.

When de Loys finally returned home with the only remaining evidence, a single photography which he treasured in his notebook, he forgot about his annoying encounter with the unknown monkeys. Only years later a friend, the Swiss anthropologist George Alexis Montandon (1879-1944), accidentally rediscovered the photo.

Fig.2. The notoriously photography of de Loys´ ape - Ameranthropoides loysi, from MONTANDON 1929. Note that there exist many versions of the image cropped by the borders, magnifying the impression left by the animal.

Considering the supposed dimension of the box (45-50cm high) visible in the photography the height of the animal was estimated to range from 150 to 160cm.
This seemed to confirm the measurements by Loys (157cm) and based on the dimension and the unusual human-like characteristics, especially the missing tail, in 1929 Montandon published a detailed description of the ape, which he considered a genuine species named "Ameranthropoides loysi", de Loys' American human-like ape.

The animal in the photography displays characteristics that are not found in the monkeys of the new world, like the upright posture, the absence of a tail and 32 teeth (after the description of de Loys). Montandon was fascinated from this sensational discovery of a supposed unknown ape species and began to collect anecdotes and legends of great apes present in remote places of South America (not specifically the region of the supposed encounter).
In two stone statues of the Maya period large, 1,5m high apelike figures are pictured. Among the tribe of the "Caribi" of Guyana there is a widespread belief in the "kanaima", demons which roam the jungle armed with clubs, assaulting whoever dares to enter their reign. In Colombia these creatures are called "didi" and described as half man and half monkey. In Brazil and Venezuela there are legends of the "vastiri".
Author and collector of curious natural history P.H. Gosse reports in 1861:
"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."
In the book "Natural History of Guiana", published by Dr. Edward Bancroft in 1769, there is a description of an encounter with a creature like an "orang-utan", and naturalist George Edwards in "A study of anthropoid life" (1757) depicts a strange ape-like creature resembling the modern photography.

However this publication of Ameranthropoides became accepted only by the French scientific establishment, in contrast it aroused a violent controversy by scientists from Great Britain and North America, the eminent English naturalist Sir Arthur Keith for example affirmed that the photo showed only a species of spider monkey - Ateles belzebuth native in the region- with the tail deliberately cut off or hidden in the photography.

Spider monkeys are a typical element of the South American fauna; however the largest known species reach 110cm height standing on the hind limbs, De Loys ape was with the estimated 157cm considerable larger. The only known fragmentary remains of such a large spider monkey species (with an estimated weight of 25 kilograms more than twice the weight of modern spider monkeys) are those of Protopithecus brasiliensis, the "primitive monkey of Brazil", a Pleistocene species discovered by the Danish naturalist Peter W. Lund in 1838 in the Brazilian region of Bahia.

In 1990 however an American cryptozoological expedition seemed to confirm Montandon´s ethnobiological research, the locals of Venezuela told the expedition about large red monkeys and recognized the ape in the photo as momo grande, as "big ape", a supposed large unknown spider monkey species.
However also this expedition could not provide hard evidence apart rumours of supposed encounters or unrecorded tracks of large monkeys.

The simplest explanation, the possibility that the photo was a fraud was refused on base of the good reputation of De Loys:

"It is sure that Francois de Loys was a man of strict science and responsibility, optimistic and friendly and featuring an intrepid spirit of adventure. It seems unlikely that such a scientist may have perpetuated the fraud of the Ameranthropoides only to gain fame. [...] There are sufficient reasons to affirm that de Loys was not a liar, especially one unimpeachable document as the original photo taken at a time when photography and image manipulation did not exist at all."

VILORIA et al. 1998 & 1999

This statement is surely to optimistic, photo manipulation is as old as the art of photography and the dimension or characteristics of the animal in many cropped versions of the photography can not be compared to other objects apart from the strange box.

De Loys himself was very reluctant promoting the story, in the official publication of 1929 by De Loys himself about the geological expedition there is no mention of the creature or subsequent research, he published only, hustled by Montadon, an article in the Illustrated London News.

In 1998 Pierre Centlivres and Isabelle Girod finally published an article suggesting that the entire story was an idea by anthropologist Montandon.
Montandon was strongly influenced by racist ideas of human evolution popular at the time; he proposed a polyphyletic origin of humans and considered the various human races descending from various 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 hypothesis.

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 view is supported by a detail in the complete view of the photo - there are stumps of non-native, cultivated banana trees visible, it is highly improbable that in the middle of the untouched jungle, supposed location of the encounter, banana trees can be found.

In the July-August edition of 1999 the Venezuelan scientific magazine "Interciencia" published a letter send in 1962 from a certain 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 say something, it has no tail because it was cut off.
I can assure you this, gentlemen, because it was before me that the amputations take place.
Who is speaking here in 1917 was working in a camp of the oil exploration industry 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 a 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 shot because he betrayed France, his homeland.

Sincerely, Your friend Enrique Tejera."

If the myths and rumours of large ape-like creature in South America have a zoological explanation, the photo of de Loys surely has nothing to do with them.
Despite his role in the pranke (he contributed the photo and the story and later never resolved the case), he 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 to young, on October 16, 1935.


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

GOSSE, P.H. (1861): The Romance of Natural History. 4th ed. Boston, Gould and Lincoln, New York: 280-281
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

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

Online Resources:

ROSSI, L. (13.12.2004): La Scimmia di Loys. (Accessed 16.01.2011)

1 comment:

  1. I believe, I always have very much believed this photograph!


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