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.
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.
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.