When you reverse the order. These two sentences mean the same thing: The human's diet. The diet of the human.

The daily diet of early humans > is more formal. More likely in a text book of anthropology etc. Early humans' daily diet > is a little less formal but is fine, and will be found in that anthropology book too > as an alternative to the other style. The daily diet of Moira = Moira's daily diet

In English, you can use both "of" and possessive 's' to show ownership or association, but they are used in slightly different contexts. 1. Possessive 's is typically used when referring to people, animals, or groups: * "John's car" * "The dog's bone" * "The teacher's book" 2. "Of" is often used for inanimate objects, abstract concepts, or when the possessive is a bit more formal or complex: * "The color of the sky" * "The top of the mountain" * "The daily diet of early humans" In your example, "The daily diet of early humans" is a bit more formal and emphasizes the diet itself rather than the ownership. You could also say "Early humans' daily diet," which is less formal and more direct. Both are correct, but the choice depends on style and emphasis.