Evidence of early hominids and other less advanced proto-human or human groups shows a pretty significant amount of calories came from meat. Some suggest 60-80% of calories came from proteins, largely meat, at various times in history.

Example source:

https://onlinelibrary.wiley.com/doi/10.1002/ajpa.24247

A contradictory source says meat was less prevalent but still at 40-50%:

https://asu.pure.elsevier.com/en/publications/the-diet-body-...

Both of these estimates are way higher than what we know people eat today, where meat and dairy are 18% of worldwide calorie consumption (27% in the US).

So I think the abundance we see today is actually due to the availability of non-animal dietary sources.