Ameranthropoides loysi, better known as de Loys’s ape, is the subject of one of the most famous photographs in cryptozoology. It shows a large, tailless, ape-like animal propped up dead on a wooden crate in the forests of the Venezuela–Colombia border. In 1929 it was announced as an unknown American ape, even a possible ancestor of Native Americans. Nearly every scientist who has examined the case since has concluded that it is a spider monkey, and that the story was a hoax with an ugly motive behind its promotion.[1][2]
| Common name | De Loys’s ape |
|---|---|
| Scientific name proposed | Ameranthropoides loysi (Montandon, 1929) |
| Photographed | 1920, near a tributary of the Tarra River, Venezuela–Colombia border |
| Claimed height | 1.57 m (about 5 ft 2 in) |
| Most likely identity | Spider monkey (genus Ateles), probably with its tail hidden or removed |
| Status | Not recognized; widely considered a hoax |
The expedition and the photograph
François de Loys was a Swiss oil geologist who led a petroleum-prospecting expedition along the Colombia–Venezuela border, near Lake Maracaibo, from 1917 to 1920. The expedition was a disaster, and only a handful of its members survived.[1]
The hardships were real. Of the roughly 20 men who set out, only four survived, the rest lost to disease and to violent clashes with Indigenous groups defending their territory. Whatever happened at the Tarra River, the photograph was taken in the middle of a grim and exhausting ordeal, and de Loys did not publicize it for almost a decade.[1]
According to de Loys’s later account, in 1920 two large animals, a male and a female, approached the party’s camp on a tributary of the Tarra River. At first he took them for bears. The men shot at them, killing the female and wounding the male, which escaped. They propped the body on a crate with a stick under its chin and photographed it. De Loys said the animal was 1.57 meters tall, had 32 teeth, and had no tail. Its skin and bones were lost, and only one photograph survived.[1][3]
Montandon’s “American ape”
The photograph sat unnoticed until 1929, when the French-Swiss anthropologist George Montandon found it among de Loys’s papers. He gave the animal the scientific name Ameranthropoides loysi and presented it to the French Academy of Sciences and in the Illustrated London News as a great ape of the Americas.[1][3]
Montandon used the find to support his theory of “hologenesis,” which held that each human race had evolved separately from a different ape, with an American ape as the ancestor of Native Americans. His ideas are now widely regarded as products of his racist views. He later became a notorious collaborator and antisemitic propagandist in occupied France.[1][4]
The case against the ape
- It looks like a spider monkey. The long limbs, the face, the hair and the body proportions all match a spider monkey, a large South American monkey common in the region. The paleontologist Darren Naish identifies it as a white-fronted spider monkey (Ateles belzebuth).[2]
- There is no scale. No person, ruler or familiar object appears next to the animal, so its claimed height of 1.57 m cannot be checked. Spider monkeys are much smaller, at around a meter or less.[1][2]
- The tail question. The anatomist Arthur Keith pointed out in 1929 that the animal’s back is not shown, so the “missing” tail cannot be confirmed, and that the photograph does not establish size. He argued that de Loys had passed off an ordinary spider monkey as something exotic.[5]
- A friend’s testimony. In 1962, Enrique Tejera, a Venezuelan physician who had known de Loys, wrote that the photographed animal was in fact a pet spider monkey that de Loys had kept and that had died, and that the story was a joke.[2]
- Later review. The primatologist Philip Hershkovitz also judged de Loys’s account unreliable, and Venezuelan researchers reviewing the case in 1998–99 reached similar conclusions.[1]
Montandon’s motive and fate
The 1929 announcement makes more sense once Montandon’s goals are clear. His theory of hologenesis needed a large ape in the Americas, because it claimed that each human “race” descended from a different ape on its own continent. A tailless, human-sized primate from Venezuela fit that requirement almost too neatly, and he named it, defended it and published it in three French scientific outlets within months.[1][2]
Montandon’s later career confirms how closely his science was tied to his politics. In the 1930s he wrote openly racist “ethno-racial” works. During the German occupation of France he became a prominent collaborator and antisemite, and he helped produce the propaganda exhibition Le Juif et la France. On 30 August 1944 he and his wife were shot by the French Resistance. [9] Historians of science now treat Ameranthropoides as a case study in how a weak specimen can be inflated to fit an ideology.[6]
Which spider monkey?
If the animal was a spider monkey, which one was it? Darren Naish compares it to the white-fronted spider monkey (Ateles belzebuth). The spider monkey of northwestern Venezuela and neighboring Colombia, including the Serranía de Perijá on the western side of the Maracaibo basin, is the closely related brown spider monkey (Ateles hybridus). It is now critically endangered, with perhaps 3,000 left, because of deforestation and hunting.[2][7]
Either species fits what the photograph shows: long arms, a rounded head, a prominent belly, and a tail that is either hidden behind the body or was removed. Spider monkeys are among the few New World monkeys that regularly sit and move upright, which could have helped de Loys’s men see the animals at first as “bears” or something human-like. Adult brown spider monkeys weigh about 7.5 to 9 kg and measure 35 to 70 cm in head-and-body length, plus a tail of about 75 cm. Without a person or object for scale, the 1.57-meter height rests entirely on de Loys’s word.
The verdict of later historians
Two Venezuelan researchers, the zoologist Ángel Viloria and the primatologist Bernardo Urbani, together with the geologist Franco Urbani, spent years retracing de Loys’s life and expedition. Their work culminated in a 2009 book whose title calls Ameranthropoides loysi “the history of a primatological fraud.” The science writer Robert Silverberg included the case in Scientists and Scoundrels, his study of scientific hoaxes and errors, under the title “The Case of the Venezuelan Ape Man.”[6][8]
Why the case still matters
De Loys’s ape is a lesson in how a single photograph, with no specimen, no scale and a convenient story, can be turned into scientific “evidence,” and how easily a claim can be put to use for prejudice. The case is still cited in cryptozoology, but the weight of evidence points firmly to a dead spider monkey.
For an African “ape-man” report with no photograph at all, see the Agogwe.
References
- “De Loys’s ape,” Wikipedia, citing G. Montandon (1929) in the Journal de la Société des Américanistes 21 and Comptes Rendus; Viloria, Urbani and Urbani (1998, 1999); D. Bressan (2016); and C. Kummer (2025).
- Darren Naish, “De Loys’ Ape and what to do with it,” Tetrapod Zoology, Scientific American Blogs. scientificamerican.com.
- François de Loys, “A Gap Filled in the Pedigree of Man?”, Illustrated London News (15 June 1929).
- C. Kummer, Swiss National Museum blog (2025), as cited in Wikipedia.
- Arthur Keith, article in Man 29, no. 100 (1929): 135–136.
- Ángel L. Viloria, Franco Urbani and Bernardo Urbani, Ameranthropoides loysi Montandon 1929: The History of a Primatological Fraud (Buenos Aires: LibrosEnRed, 2009), as cited by Naish (ref. 2); see also D. Bressan, “De Loys’ Ape Was a Well Played Anthropological Fraud,” Forbes (31 January 2016).
- “Brown spider monkey (Ateles hybridus),” Wikipedia, citing the IUCN Red List assessment (Critically Endangered).
- Robert Silverberg, “The Case of the Venezuelan Ape Man,” in Scientists and Scoundrels: A Book of Hoaxes (Lincoln: University of Nebraska Press, 2007), 171–187.
- “George Montandon,” Wikipedia.
Correction note (October 2026): This entry was rewritten from the published record. An earlier version described the animal’s “intelligence and awareness” and linked it to local folklore about ape-like creatures without sources; it also did not explain the evidence that the photograph shows a spider monkey. The illustration above is an artistic impression, not the original photograph.