Re: Stephen Jay Gould and progress

Mitchell Porter (
Mon, 13 Jan 1997 11:11:54 +1000

[Tony Csoka]
> I mean, the same chemicals that composed the "primordial soup" from which
> life arose on this planet, and perhaps elsewhere, would probably still be
> around today whether life arose or not. WHAT "SELECTIVE ADVANTAGE" IS THERE

The reason why the genome _can_ become more complex would just be that
DNA is a polymer, and can get longer and longer. Probably there's an
upper limit to the length of a single chromosome, but you can add new
chromosomes. Mechanisms of length-increase probably involve insertion
or retention of multiple copies of DNA; e.g. extra copies of chromosomes
are made at replication, or perhaps mRNA is spliced back into the genome
somewhere by reverse transcriptase.

One reason bigger genomes could be advantageous: by allowing for more
adaptable organisms. The more useful add-ons an organism has, the more
adaptable it is liable to be, but each add-on will require extra genes.
A ceiling on genome length is probably a ceiling on adaptability (until
brains get into the picture).