There's this example from history, if the historian Moroni's account from AD400 is to be believed: 7 And now I write somewhat concerning the sufferings of this people. For according to the knowledge which I have received from Amoron, behold, the Lamanites have many prisoners, which they took from the tower of Sherrizah; and there were men, women, and children. 8 And the husbands and fathers of those women and children they have slain; and they feed the women upon the flesh of their husbands, and the children upon the flesh of their fathers; and no water, save a little, do they give unto them. 9 And notwithstanding this great abomination of the Lamanites, it doth not exceed that of our people in Moriantum. For behold, many of the daughters of the Lamanites have they taken prisoners; and after depriving them of that which was most dear and precious above all things, which is chastity and virtue— 10 And after they had done this thing, they did murder them in a most cruel manner, torturing their bodies even unto death; and after they have done this, they devour their flesh like unto wild beasts, because of the hardness of their hearts; and they do it for a token of bravery.

These were the extinct people of the Nephites from The Book of Mormon