“When the Strong Outbreed the Weak” →

An ex­per­i­ment in se­lect­ive breed­ing for a de­sir­able trait shows that the simple ap­proach does not pro­duce the ex­pec­ted out­come:

The pur­pose of the ex­per­i­ment was to in­crease the egg-lay­ing pro­ductiv­ity of hens. The hens were housed in cages with nine hens per cage. Very simply, the most pro­duct­ive hen from each cage was se­lec­ted to breed the next gen­er­a­tion of hens.

If egg-lay­ing pro­ductiv­ity is a her­it­able trait, then the ex­per­i­ment should pro­duce a strain of bet­ter egg lay­ers, but that’s not what happened. In­stead, the ex­per­i­ment pro­duced a strain of hy­per-ag­gress­ive hens[…]. There are only three hens [left in the fi­nal cage] be­cause the oth­er six were murdered and the sur­viv­ors have plucked each oth­er in their in­cess­ant at­tacks. Egg pro­ductiv­ity plummeted, even though the best egg-lay­ers had been se­lec­ted each and every gen­er­a­tion.

The reas­on for this per­verse out­come is easy to un­der­stand, at least in ret­ro­spect. The most pro­duct­ive hen in each cage was the biggest bully, who achieved her pro­ductiv­ity by sup­press­ing the pro­ductiv­ity of the oth­er hens. Bul­ly­ing be­ha­vi­or is a her­it­able trait, and sev­er­al gen­er­a­tions were suf­fi­cient to pro­duce a strain of psy­cho­paths.

There are many, many in­ter­est­ing things to learn here. Most dir­ectly, this is a les­son in just how com­plex bio­logy is. But there may also be les­sons here for hu­man so­ci­ety:

In a par­al­lel ex­per­i­ment, Muir mon­itored the pro­ductiv­ity of the cages and se­lec­ted all of the hens from the best cages to breed the next gen­er­a­tion of hens. […] Egg pro­ductiv­ity in­creased 160% in only a few gen­er­a­tions, an al­most un­heard of re­sponse to ar­ti­fi­cial se­lec­tion in an­im­al breed­ing ex­per­i­ments.

It’s easy to cred­it the dir­ect­or with the suc­cess of a great movie. But have have you ever watched the en­tire list of cred­its at the end of your fa­vor­ite movie? Mod­ern movies do not spring, fully formed, out of the mind of the dir­ect­or, as Athena from Zeus. Nor are they simple col­lab­or­a­tions among the dir­ect­or and act­ors. They are the products of small armies of people, work­ing col­lect­ively to pro­duce something far great­er than any one of them could achieve on his or her own. The same is true of any great achieve­ment.