Remember that eating grains does not give any energy if they are not
treated in some way to open the cellulose walls. Heated for example.

Probably much of what was eaten in paleo times was a compromise between
health pros and cons, and energy spent/gained. There probably has never
been a completely "safe" diet eaten by anyone.

Animals usually prefer stable food sources over ones that are plentyfull
sometimes and little sometimes.

- Hans