In Evolution, Adaptability Beats Fitness

The longest con­tinu­ous evol­u­tion exper­i­ment was star­ted in 1988 and is still ongo­ing. The study, examin­ing the “evolvab­il­ity” of Escheri­chia coli (E. coli), has recently sur­passed 52,000 gen­er­a­tions and has had a sample of the pop­u­la­tion frozen and saved every 75 days (every 500 gen­er­a­tions). The wealth of data obtained is fant­ast­ic and these frozen ancest­or­s have been the focus of a recent study that set out to find wheth­er the even­tu­al “evol­u­tion­ary win­ners” dis­played signs of their genet­ic superi­or­ity hun­dreds of gen­er­a­tions earli­er.

To the research­er­’s sur­prise, the bac­teri­al win­ners in fact showed the abso­lute oppos­ite: they were far inferi­or to the strains of bac­teria that died out in later gen­er­a­tions. To explain this they dis­covered that while these ancest­or­s were con­ven­tion­ally less evol­u­tion­ar­ily fit (they repro­duced at a much slower rate), these “evol­u­tion­ary winners“ were much bet­ter at adapt­ing to cir­cum­stances and at tak­ing advant­age of bene­fi­cial muta­tions. Adapt­ab­il­ity trumped fit­ness.

“[The idea of] selec­tion for evolvab­il­ity has been in the air for a long time, but this is one of the first real sys­tem­at­ic and expli­cit demon­stra­tions of this actu­ally hap­pen­ing,” said evol­u­tion­ary bio­lo­gist and pop­u­la­tion genet­i­cist Michael Desai of Har­vard Uni­ver­sity […]

The first sur­prise came when the team com­pared the fit­ness of four strains – two EWs [even­tu­al win­ners] and two ELs [even­tu­al losers] – and found that while all four strains had sig­ni­fic­antly high­er fit­ness than the ances­tral strain, the ELs appeared more fit than the EWs. Com­par­ing the four strains dir­ectly con­firmed the res­ult: The two EW strains were at a sig­ni­fic­ant dis­ad­vant­age to the ELs. If these strains had not accu­mu­lated any more muta­tions, the research­ers estim­ated the EWs would have gone extinct in just 350 addi­tion­al gen­er­a­tions. […]

The res­ults sug­ges­ted that the EWs, while ini­tially at a dis­ad­vant­age, pre­vailed in the long-term because they were more likely to acquire more bene­fi­cial muta­tions. In oth­er words, the EWs had great­er evolvab­il­ity.

This seems like evol­u­tion­ary evid­ence for the premise of Tim Har­ford’s latest book, Adapt.

1 thought on “In Evolution, Adaptability Beats Fitness

  1. Pingback: Programming Darwinism - IT Hare on Soft.ware

Comments are closed.