The best parts of Spencer’s book are when he reaches back into antiquity to talk about the birth of vegetarianism, but this also is where he makes bold statements with minimal documentation about his sources. To simplify, he puts the source of abstaining from meat in ancient Egypt, as something priests did to get closer to the gods, to become more godlike themselves since gods couldn’t eat but simply smelled the smoke of the burnt offerings. Pythagoras is the first person to go on record as a vegetarian, but he lived ~580 BC to the early 500s BC and accounts of his life started being committed to paper hundreds of years later. Jokes about vegetarians/Pythagorians abounded in ancient Greek comedies (and continue, of course, to this day. I started reading this book because of the Pythagorean fart joke Melville makes early on in Moby-Dick).
Spencer asserts that “vegetarianism is one of the signs of a radical thinker, the individual who criticizes the status quo, who desires something better, more humane and more civilised for the whole of society. It makes meat-eaters uneasy and they often react aggressively.”
Apparently, things went off the rails for vegetarians after Christianity got hijacked by Paul/Saul. Dark ages ensued, then here comes the Renaissance where Leonardo Da Vinci was an outspoken critic of eating animals. Yadda yadda long lists of famous vegetarians: GB Shaw, Hitler, Voltaire, Gandhi, Tolstoy, Benjamin Franklin, etc. and then the advent of the factory farm where everyone should know better than to eat hormone-pumped, disastrously maintained animals.