Suppose someone with a time machine decided to go way back in time, to the earliest ages of the Earth, in fact. What is the earliest period in the Earth’s history in which a human being could theoretically survive for an extended period? (I assume that, during the very earliest stages of its history, the Earth would have been uninhabitable for advanced life such as our species due to such things as not even being solid, having no atmosphere (or one without any oxygen in it), suffering too many meteoric bombardments, having no water on it etc. Of course, even when plant and animal life appeared on Earth, there is no way of knowing whether it would have been edible for humans or not, but assume for the sake of this exercise that at least some of it would have been.)
Basically, you’re asking when in Earth’s history, did the atmosphere and climate begin to favor the survival of large land animals, and I’d have to say it was well after the “Cambrian explosion”, some ~540-570 million YA, when huge numbers of new species of multicellular animals becan appearing at an astounding rate. By this point, oxygen breathers had evolved, so the atmosphere had at least a significant amount of oxygen.
I’ll offer this. After the dawn of the land animals, they almost immediately started to taste just like chicken.