The Chinese during the great leap forward practiced cannibalism on a scale not seen since the Aztecs of meso America. During the siege of Stalingrad there was also much cannibalism, same for the Pacific theater in Burma. Humans are still animals at heart when we get hungry enough those with a real survival instinct will kill and eat those who lack that killer instinct. Thus keeping those strong genes in the gene pool it’s biologically an advantage to have those killer genes when the times are tough at the species level forget culture. Culture is a product of the species being successful enough to get past basic survival mode and into specialized roles and sedentary lifestyles.