Maybe the other way around? Like the genes that survived were the ones that coded for curiosity in terms of food; encouraging early humans to explore and find more nutrient rich food to feed bigger brains. So not that our bodies ‘told us’, but we selected for the humans with those genes, and they were the ones that won out in the end.

Psycho mantis?

I agree, that’s a good way to put it

Yes this. And is a drug that makes you happy really science fiction? There are plenty that work on dopamine, serotonin and oxytocin receptors. Though I suppose happiness is something more nebulous and complex than a handful of chemicals.