Most people have consumed animal proteins the catch is they weren't eating a lot meat regularly. One of my ancestors was upper middle class when he migrated to the USA and founded a small city. His journal talks about his meals and as a wealthy person with a dairy farm he still mostly had stew and rarely ate steak. He wasn't eating animals all the time and that was 1840-80s. We need to go back to a time when eating a whole chicken among a family of four in a single meal almost never happened IF we continue farming animals which as you noted is a climate change nightmare.