jmclatchie

This is the sort of recurring pattern that one might expect to see in designed systems, but it is more surprising in stochastically evolved systems. It therefore suggests that operon regulation is best understood as the product of engineering rather than blind, unguided processes.

The design logic is the same. And yet, these two systems are not evolutionarily related to one another — as evidenced by the fact that the enzymes encoded by these two operons do not share sequence homology, indicating distinct evolutionary origins.

The headline that prompted me to read this paper claimed that the study “shows how bacteria evolved powered-up propellers.” But the paper does not do this at all. All it shows is another example of a flagellar protein that bears homology to a non-flagellar protein.

The origin of spliceosomal introns represents a significant challenge to an evolutionary account of their origins. While the hypothesis that group II introns from bacterial endosymbionts gave rise to eukaryotic introns is the prevailing explanation, it faces a series of substantial obstacles.