They do naturally behave like something, because they have a nature, and a tendency to behave along certain lines - regardless of whether or not we've bred them to be that way.

Hens can lay eggs for a good 13 years in some cases, and can live quite a bit beyond their egg-laying days as well, without peril.

Their peril comes when I decide "I'm going to eat that chicken." And, I kill the chicken in a lot nicer way, likely, than you or I will die, when we do.