FYI that study has been successfully debunked shortly after it was written.

There are more recent claims of doubt against more meat = large brain though.

The fact still is that both meat and animal milk were a huge impact in early homo life.

It's entirely possible that our capacity of language and advanced learning stems from non dietary sources.

https://www.nbcnews.com/science/science-news/eating-meat-make-us-human-new-research-casts-doubt-rcna13315