These indigenous people call themselves Aché, an expression that means "real person". They attract attention because of the light colour of their complexion, eyes and beards, which differentiate them from the peoples of the eastern jungle. It has also been suggested that they descend from exotic peoples, such as the Vikings, the Japanese, and other Asian peoples. The Guarani tribe refers to Aché in a derogatory way as 'Guayaki', which literally means 'forest rat'.

They Aché live in the eastern region of Paraguay, more precisely in the Cordillera del Mbarakajú, which divides the basins of the Paraguay River and Paraná River, and other unspecified sylvan areas.

There are several known groups of Aché with their own cultural and dialectal characteristics, which have not yet been systematically studied. According to the 3rd National Census for the Population and Housing Situation of Indigenous Peoples of 2012, there are approximately 2,000 Aché.

In the current settlements, the Aché use the colloquial 'Guarani-Paraguayan', but they still retain their Aché language, which includes a vast vocabulary of jungle-specific words that have no equivalent in any other idiom.

The Aché vigorously resisted the whites and were therefore subjected to brutal persecution. In 1941, the scholar Miraglia wrote: “For the Paraguayan peasants of the east, killing an Aché is not only not a crime, but a worthy action, like hunting a jaguar'. Twenty years later the same Miraglia reported that the situation had worsened because 'the Aché, whose hunting grounds are progressively diminishing, driven by hunger, plunder maize and mandioca plantations and slaughter cattle for food... the slavers organise real hunting parties in search of them.”

The Aché have suffered repeated abuse from colonies, ranchers and large landowners. The ever-increasing need to escape these abuses probably led some Aché groups to adopt extreme practices such as the voluntary killing of individuals who were too old or sick and were a burden for the survival of the group.

Populating a territory of twenty thousand square kilometres, they were confined to two reserves of just over 50 square kilometres. The Kuetuvy Aché were driven out of the Mbaracayú region in the 1970s, but managed to return in the 2000s.

Before the Aché were forced into a reserve, they were nomadic, and many of their habits were based on high speed of movement, using temporary shelters as dwellings. They travelled in small groups, organised into politically independent communities that controlled their hunting grounds. The communities were based on kinship networks that shared food and shelter.

Political power among the Aché was non-authoritarian and non-coercive. Their berugi chief was chosen for his ability to speak in public. Decisions were taken by consensus and if the leader was unable to meet the needs of his people, he allowed a successor to be chosen.

In the reserves, the political situation was reversed and the younger men began to dominate the older men, who held political power in the forest, because the younger men adapted to the new customs, technologies and the Spanish language more quickly.

The relationship between humans and animals is fundamental in the Aché worldview. So much so that their first names are formed from the name of an animal species, to which the suffix -gi is added. The naming process precedes birth and is carried out in the last months of pregnancy by the mother, who chooses the animal out of different types of game. Through the choice of the name of the hunted animal, a social relationship is created between the woman, her husband and the hunter who offered her the chosen meat.

Meat is the basis of their diet and the men who procure it are respected for their hunting skills. Their bows are very strong and over two metres long, made of Pindò palm wood. The women extract fibre from palm trees and collect fruit and insect larvae. They also look after the children and are responsible for moving the camp, which occurs almost daily. Food is prepared and shared equally among all group members.

Polygamy is accepted by both sexes and abortion is allowed, but incest is prohibited.

In the reserves, the Aché have developed a new way of life. For example, in the reserve of Chupa Pou, there have been a school, a medical clinic, a shop and a football pitch since 1989. Over time, the younger Aché have learned the technique of "slash and burn" farming and domestic animal breeding.

In 1989, Chupa Pou was legally recognised as a reserve, and the community started to run a shop cooperatively. However, this has not changed their living conditions as they remain among the poorest people in Paraguay.