It’s worth remembering that the chicken experiment was specifically designed to elicit that effect, and chickens are unusual in being confined to extremely small cages with other chickens. That doesn’t happen with cows or apples or wheat or… As far as I know, animal/plant breeders typically totally ignore such indirect genetic effects/group-level effects (or even model them away, absorbing them into fixed/random effects), along with ignoring apparently vital stuff like epistasis/dominance, and yet the dumb simple selection methods based on additivity work fine and still realize all the improvements they are supposed to. Yields go up reliably every year.
It’s worth remembering that the chicken experiment was specifically designed to elicit that effect, and chickens are unusual in being confined to extremely small cages with other chickens. That doesn’t happen with cows or apples or wheat or… As far as I know, animal/plant breeders typically totally ignore such indirect genetic effects/group-level effects (or even model them away, absorbing them into fixed/random effects), along with ignoring apparently vital stuff like epistasis/dominance, and yet the dumb simple selection methods based on additivity work fine and still realize all the improvements they are supposed to. Yields go up reliably every year.