At which point does an egg of non-chicken become an egg of chicken?
Is a “chicken egg” an egg laid by a chicken, or an egg that will hatch into a chicken?
The former, otherwise it would be “chicken’s egg”.
Incorrect, a “chicken’s egg” would be an egg in the possession of a chicken, which would be the egg a chicken lays. The “first chicken” did not hatch out of an egg laid by a chicken because they didn’t exist.