First comes some gene A which is simple, but at least a little useful on its own, so that A increases to universality in the gene pool. Now along comes gene B, which is only useful in the presence of A, but A is reliably present in the gene pool, so there’s a reliable selection pressure in favor of B. Now a modified version of A arises, which depends on B, but doesn’t break B’s dependency on A/A. Then along comes C, which depends on A and B, and B, which depends on A* and C.
Can anybody point me to some specific examples of this type of evolution? I’m a complete layman when it comes to biology, and this fascinates me. I’m having a bit of a hard time imagining such a process, though.
Sure. Your cells have two methods for copying DNA. One of them is fast and highly accurate. The other is quite slow and makes mistakes several times more often.
The chemical structure of the accurate method is basically an order of magnitude more complex than the inaccurate one. It seems likely that the inaccurate method is the remnant of some previous stage of development.
The inaccurate method has stuck around because the error checking on the accurate method also causes the process to stall if it hits a damaged segment. At which point the strand being copied gets kicked over to the older machinery.
The new method, being significantly more complex, is dependent for assembly on significantly more complicated structures than the old method, structures which could not have been created without the old method or something like it. Figuring out exactly how far down the stack of turtles goes is tricky though since all the evidence has long-since decayed. Maybe as we get better at decoding DNA we’ll find leftover scraps of some of them lurking in the seemingly-unused sections of various genomes.
Can anybody point me to some specific examples of this type of evolution? I’m a complete layman when it comes to biology, and this fascinates me. I’m having a bit of a hard time imagining such a process, though.
Sure. Your cells have two methods for copying DNA. One of them is fast and highly accurate. The other is quite slow and makes mistakes several times more often.
The chemical structure of the accurate method is basically an order of magnitude more complex than the inaccurate one. It seems likely that the inaccurate method is the remnant of some previous stage of development.
The inaccurate method has stuck around because the error checking on the accurate method also causes the process to stall if it hits a damaged segment. At which point the strand being copied gets kicked over to the older machinery.
The new method, being significantly more complex, is dependent for assembly on significantly more complicated structures than the old method, structures which could not have been created without the old method or something like it. Figuring out exactly how far down the stack of turtles goes is tricky though since all the evidence has long-since decayed. Maybe as we get better at decoding DNA we’ll find leftover scraps of some of them lurking in the seemingly-unused sections of various genomes.
Coincidentally, Quanta has an article on a modification of RNA World hypothesis arguing something similar: https://www.quantamagazine.org/lifes-first-peptides-may-have-grown-on-rna-20220524/