This, of course, means that humans are not natural vegetarians. The fossil record. The supporting evidence here includes isotope analysis of fossils, providing further evidence of consumption of animal foods. Comparative anatomy of the human gut.
Plant foods are poor sources of EFAs.
This strongly suggests adaptation to foods that include preformed long- chain fatty acids, i.e., fauna. Taurine synthesis rate. Slow conversion of beta- carotene. Plant foods available in evolution were poor zinc and iron sources. This suggests that the nutritional requirements for iron and zinc were primarily met via animal foods during human evolution.