I thought this was super interesting:
For 2 million years, humans ate meat and little else -- study | The Times of Israel
Looks like protein became scarcer around 85 thousand years ago, but before then humans ate only meat for 2 million years!
As someone else already mentioned, if you think this is interesting you should check out Sapiens: Sapiens: A Brief History of Humankind - Wikipedia
The first 1/3rd of the book is all about this.