Before the Spaniards arrived in Peru, the Incas were quite busy making war on other natives. At the time of this anecdote, the powerful Inca Huaina Capac was busy conquering his neighbors with an impressive army of forty thousand men. He had a score to settle with the people of Tumbez, who had killed his father's ambassadors many years before. The following is quoted from The Incas: The Royal Commentaries of the Inca Garcilaso de la Vega, Orion Press, New York (1961), pp. 261-262.
The people of Tumbez were more dissolute and included to be vicious than all the other inhabitants of the coast. Their chiefs lived lazily surrounded by a court of buffoons, dancers, and mountebanks, and they also indulged in the odious vice of sodomy; they worshiped lines and tigers to which they sacrificed human hearts, and were both strictly obeyed by their subjects and feared by their neighbors. None of these things, however, kept them from surrendering at the Inca's first summons, so great was their fear of his military might...
The Inca entered Tumbez where he ordered construction of a fortress, a Temple of the Sun and a convent for virgins. Once these were finished, he set out for the interior, in order to go to punish, as he had promised his dying father he would do, those who had killed the latter's captains and ministers. He did not actually enter these provinces but settled on their frontiers, from where he sent ambassadors to summon the guilty to come to him, to receive their punishment; and they hastened to obey, so greatly were they terrified both by the heinousness of their crime and by the Inca's arrival.
Huaina Capac had specified that he wanted to see all the curacas, amabassadors, councillors, captains, and other notables in the delegation that had asked his father for the ministers whom, later, they had murdered. And they all came together, as he had bid them to do. They were received by an aide-de-camp, who gave them a long reprimand in the name of the king, pointing out their treason, their perfidiousness, and their cruelty. "You should worship the Inca and his ministers," he said, "because the former sent you the latter to allow you to emerge from your state of ignorance and become men. But you cruelly murdered your benefactors, insulting, by this gesture, the king, who is the son of the Sun. The heinousness of this dual crime deserves an equally severe punishment. Your nation deserved to perish entirely, without consideration for age or sex. But the great Inca, Huaina Capac, who is by nature humane and kind, and worthy of the name of Huacchacuyac, or friend to the poor, is willing to forgive all of your humbler subjects. As for you who are present here, however, you who perpetrated and carried out this crime, and therefore deserve to die a hundred deaths, with all your kith and kin, our king grants you, too, unusual grace; for he has ordered that only one out of ten among you should be slaughtered, in order to let it be known that, mercy notwithstanding, there are crimes that bear within themselves their own punishment. You shall therefore draw lots, in groups of ten each, to determine which shall die, in order that none may accuse us of having favored certain among you to the detriment of others."
Such was the Inca's first sentence. Then...he ordered that all the curacas and nobles of this province should have two upper and two lower teeth pulled out, and that henceforth and, for all time, this operation should be performed on their descendants, in memory of and as a witness to the broken vows and the insult they had perpetrated against the great Tupac Inca Yupanqui.
The guilty ones underwent this test with great humility, considering themselves very fortunate to have been so lightly punished: because, to tell the truth, they had all expected to pay with their lives. When it was learned, in the Huancahuillca province that only the nobles and the curacas would have four teeth pulled out, what had been intended for punishment became a favor in the eyes of the people, and right away, they all voluntarily had their teeth pulled, without anybody or anything, except unforeseeable vanity, having obliged them to do so. Indeed, the custom has endured, and today, still, the people from this province are recognizable by their incomplete dentition.