Pedro Cieza de León, (c.1520 - 1554), was a Spanish explorer, born in a well-to-do family who set off at the young age of fifteen on a voyage to the newly discovered continent of America.
He stayed there, taking part in several expeditions in Colombia and Peru. After his return to Spain in 1551, he became a historian and geographer and wrote an account on his adventures (Crónica del Peru), he died shortly after at the age of thirty four.
His "Peruvian Chronicle" (that is the meaning of its title in English) is very interesting and is a good source of information for historians and researchers delving into the first days of the American conquest and the way of life of the American natives.
I have found some sources that mention Cieza de León's account saying that in it he includes a reference about ape-men that went around in pairs and had a very sharp moan or howl. I decided to check out the "real" and original sources, his Cronicle. Below is the relevant text:
In these mountains and jungles they assert that there are people so wild that they do not have home or clothes and go around like animals, killing birds and animlas with arrows which they eat.
That they do not have lords or captains and that they live in the hollows and boughs of trees in most of which, they also say (though I have not seen them), are female monkeys so large that they move about the trees, and with whom, tempted by the devil, (who always seeks the ways and places for men to commit the worst and gravest sins), these men use them as wives.
And it is said that some give birth th monsters with the heads and limbs like those of men and the hands and feet ape-like. They are, they say, small bodied and with monstrous proportons, and hairy. It seems, alas, they resemble (if it true that they exist) the devil, their father.
He goes on writing that he can not understand why ignorant men “soil themselves” with other beasts, and then mentions that while visitng the region of Charcas in 1549, he spent one night in the tent of a Spanish nobleman who told him the following:
That he had seen with his own eyes, in the mountains, one of these monsters, dead, its shape and sizes as described [above]. And Juan Vargas, a neighbor of La Paz [Bolivia. See map] told him that at Guanuco the Indians told him that they heard the howling of these demons or female monkeys”
We can clearly see that he is mentioning primitive men (maybe H. Sapiens) native Americans that lived just like they do until this day in the Amazonian jungle, hunting with bows and arrows. These primitive people however lacked huts and lived in the trees.
Furthermore it seems that he is attempting to explain the existence of some odd sightings of dead ape-men reported by the natives to the Spaniards. His explanation: unnatural mating between men and female apes resulting in ape-men offspring. Of course a sixteenth Century Spaniard would blame the devil for these sins.
Finally the howling and moaning part may be true if applied to monkeys: they may well be howler monkeys, which belong to the (genus Alouatta) and comprise fifteen species. They are one of the largest monkeys of South America. They measure up to 90 cm (3 ft.) long and have a prehensile tail. There is no other fit ape in America to play the part of seductress she-monkey.
I guess that the natives had some myth regarding ape-men and that they were the outcome of cross species mating between apes and men. This probably points at some relict homind group of men living in secluded jungle areas of South America during the early days of the Spanish Conquest.
 Pedro de Cieza de León. (1552) Obras completas CSIC, 1984 pp. 120.
The quote above is shown below in Spanish:
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