For the devepment of complex foodstuffs, it is much easier to understand if you stop thinking about it as a single invention. It's not a case of 1 day munching on grass seeds, and the next day inventing the baguette.
First you eat the seeds.
Then you pick more seeds than you need for that day and find that they get drier but stay edible. So you can pick and dry grain to use through the winter.
But it's a bit hard by the time you're getting to the end of your stock, so you try soaking it in water to make it eater to eat, and maybe bashing it up a bit so it absorbs the water better.
Then one day you get carried away chatting while bashing the grains and they are ground to powder. Which is really difficult to eat, but you don't have enough food to waste so you mix it with water to make it edible. And probably stir in some herbs, or strongly flavoured seeds to make it taste nicer.
One day, sitting by the fire eating your paste, you drop a bit on a hot stone. Can't waste food so you peel it off and eat it, and it tastes much nicer than the uncooked paste.
Then you make a big batch, to cook over a few days, and it goes a bit bubbly because wild yeast has got into it. You have invented bread. (Or beer, if you were making a fruit bread and put too much water in the mix so it's too runny to cook.)