I'm not the same person, but it's not about our physical evolution imo. It's about advances in agriculture, our understanding of nutrition and ability to supplement or fortify foods with things like vitamin B12. Without those things, trying to cut out all animal products would probably be a terrible idea. With them, it becomes a viable choice for people with a good understanding of nutrition and without health problems that clash with veganism.

Morality depends on culture. What appeared through evolution is culture, but no one culture or the right culture. What is right in one culture is wrong in another one.