I just came across another type of "wild man" that lived in the South American jungles, the Caigua (or Caaiguá). These creatures were people, since they were baptized and settled in Jesuit Missions. Unlike other putative wild men, these were not monkeys (they actually hunted monkeys).
These wild men were regarded by the more civilized Native Americans as people who lived in the jungle, savages.
Wild Men according to the Jesuits
In the late 1700s, the Spanish Jesuit missionary, Father José Guevara (1719 - 1806) wrote about these mysterious "Caaiguás" people: "their name in Guaraní [a Native American language] means wild people... men with noses like monkeys; hunchbacked that look towards the ground... short neck and so sunken that it barely protrudes above the shoulder... They live in the jungle and chase monkeys, jumping from branch to branch and from tree to tree with admirable dextrity and litheness."
That these natives also known as Caiguas or Coaiguás were human is attested by the fact that they were considered, "nomad Guaraní natives"  some of them were even placed in a Jesuit Mission:
The Spaniards controlled the natives by gathering them and settling them next to a mission (most missions were run by Jesuits). They worked for the mission in its fields or craft shops, and were indoctrinated and converted to Christianism.
These settlements were known as "Reducciones" (from the Spanish verb "reducir": subdue, subjugate, pacify). There were other means of dominating the natives which the Spaniards copied from the Inca rulers that they had overthrown: forced labor, a serf system and communal work (Mita, Yanacona and the Encomienda systems).
Father Francisco Vázques Trujillo in a letter to his superior in the Jesuit Company, wrote about them: "they are known as Caiguaras. They are a nation that lives in the jungles, that seem like little lambs. They are always looking towards the ground. Father Juan de Porras, who is in charge of this Reducción, with his good manners has taken them out of the jungle..." 
The "lamb-like" allusion is not about their appearance, but about their character (peaceful and tame). Their other physical features are quite odd: hunchbacked, sunken head (like embeded deeply in their shoulders - short necked), a gaze fixed on the ground... What can that mean?
Since they are not described as hairy and being interned in a Mission we can safely guess that they were people, odd people, but humans. Their Tarzan-like dextrity (jumping from branch to branch) is amazing indeed.
Could they be a relict tribe of hominids? (i.e. Neanderthals or H. erectus), their "primitive" appearance would have been remarkable and noticed by the Jesuits, they would have noticed that they were humans, but not exactly like us.
Just as I was posting this I came across some more information on Caaiguas, I will post this once I have read it in detail. Thanks.
 Guevara, J. "Historia del Paraguay, Rio de la Plata y Tucumán", Ed. Pedro de Angelis (1836)Book 1, part 1.
 Azara, F. (1793). "Descripción e Historia del Paraguay y del Rio de la Plata". Vol. 1
 de Gandia, E. (1929). Historia Crítica de los mitos de la Conquista Americana. B. Aires, J. Roldan y Cia. pp. 34
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