Best bit from the comments:
"But, Don, they have uncovered many, many paleolithic food processors.
"I believe they are called ruminants."
Part 2 goes into the physiological reasons why we are not vegans:
"Briefly, both of the apes closest to humans by genetic constitution (about 98% identical), chimps and gorillas, are hindgut fermenters. In chimps and gorillas, the hindgut, or colon, comprises about 52 percent of the total gut volume. It houses microbes that ferment fiber, converting it to fatty acids that supply up to 65% of the animal’s energy requirements. In contrast, in humans the hindgut comprises only about 17 percent of total gut volume, and has relatively small microbial population. At most, microbial fermentation in the hindgut can provide about 10% of human energy requirements."