[Tserisa]

Chickens do not need to be stimulated anymore to lay.

If you'll read my post it's clear that they've gone beyond that to lay constantly. "They started keeping chickens, and breeding the ones that were more likely to lay eggs when stimulated, etc. etc. until eventually the chickens were laying eggs constantly."

That is how it was selectively bred. They chose animals to breed that could be easily induced (stimulated) to lay, and then bred the ones that laid more, and then the ones that laid more.

My point is, it is a trait that has been bred into them, not a natural trait. It is not equivalent to a human period.

I have kept many many chickens, and yes, they laid plenty of eggs with no help from me! And all over the yard, since broodiness has been bred out of many breeds (and bred into others, like silkies).

It is true however, that in order to increase production in commercial laying hens all those stimulation factors I mentioned are used. It is a process called "induced molting". They change the lighting, fast the flock, and give them more calcium. This stimulates the chickens' reproductive tract to increase the egg-laying lifespan of the chickens.