Ok but what about everyone since then 

 I’m not against eating meat.  But life expectancy gets shorter as you go back in time. Our species resilience over time has been its ability to utilize various sources of food rather than one source and animal domestication was much later on our evolution than an origin story. Life thrives in therapeutic ranges of nutrients.  They can optimized but pouring more energy dense food in than required creates more metabolic byproducts than benefits. Balance is more important than “more is better”. I’m all for not weaponizing  any one food group.