Many of the tourists who have visited the Amazon have that doubt about the cannibals in the Amazon. Cannibalism was a cultural part of the ancestral ethnic groups that inhabited the Amazon and still exists in remote places like the Yavary Valley (26 days by boat from Leticia Amazonas) where there are isolated tribes of civilization.
There are still tribes that do not use any clothing
I want to quote this description taken from Eugenio Robuchon’s book “Among Cannibalistic Indians” for a better reference on cannibalism in indigenous people of the Amazon:
The tendency of these beings to cannibalism is such that they eat each other from tribe to tribe. Not counting battles, where corpses of enemies provide meat for the feast that takes place the day after the action, they always have a chance to satisfy this trend, since they keep as prisoners of war those who fall in their hands, keeping them for later dates. And these unhappy people never flee, even knowing the fate that awaits them, because they consider as an honorable distinction the kind of death to which they are destined. The day of the ceremony arrives, they kill the victim with a poisoned arrow: head and arms, the only prey for the feast, are separated from the trunk, and then the horrible culinary operation begins.
The large earthenware pot, specially reserved for the case and usually suspended from the ceiling, is lowered to the ground. The human remains are thrown in it without mutilating them, seasoned with a good quantity of red peppers, and that disgusting stew is made to boil over a low heat. Simultaneously, the manguaré begins to make its deafening sound, announcing in the distant forest the preparations for the ceremony. From all the neighboring hills the manguarés respond, and the Indians begin to arrive at the center of the feast.
All of them have been covered with their most beautiful ornaments, with multicolored feathers, with bells that tied to the knees produce a happy sound at every step. Five or six hundred Indians, men and women, populate the site, making a thundering roar, mixing their discordant cries to the shrieks of the creatures or to the howls of the dogs…
Suddenly, the noise of the manguare instrument … A great silence follows the previous shouting: the pot has been removed from the fire.
The men, the only ones who take an active part in the ceremony, sit around. The captain or chieftain grabs a piece of human flesh and after breaking it into long strands, takes it to his mouth and starts sucking it slowly, occasionally uttering a series of words supported by an affirmative heu from the rest of the crowd. Immediately he throws aside the bled flesh. Each one continues, in turn, the same operation until the day breaks. The skulls and arms, completely devoid of flesh, are immediately suspended from the ceiling above the smoke, and then the cannibals get fed up with cahuana, and by sticking their fingers down their throats, they make themselves vomit.
Re-rumble the manguare instrument, slowly at first, then very quickly, until the blows take on an overwhelming rhythm. The dance has begun, a dance from hell, where the earth trembles under the kicks of the Indians. The bells resound in a deafening way, the chants turn into atrocious howls and a nervous excitement takes hold of the Indians, produced by the influence of the coca, very similar to the ferocious madness, which dominates them during the eight days of the festival.
Cases have still been heard in very remote places where people have disappeared or been found dead. Many isolated tribes kill outsiders who invade their territory or nature reserve, they have suffered from persecution to killings by miners or loggers.
The film Cannibal Holocaust is one of the most interesting to watch and can give you an idea about cannibalism. Remember this film had no real acts but it gives an image of what could have happened many years ago.