In the RNA world of early life, or even in the preceding protein-only world, reproduction was not accurate, but only approximate. It had a relatively large error rate in copying sequences of nucleotides or amino acids (a few percent), and so was prone to “error catastrophe”, an accumulation of errors such that viability was destroyed: meaning decayed to nonsense. However, the virtue of this system was that it could easily explore the vast space of sequence possibilities, which are super-astronomical in number, and thus have great flexibity, but minimum stability.

This rapid mutation rate was somewhat moderated by the formation of hypercycles, in which already mutually catalytic cycles became tied together into larger cycles of cycles (called hypercycles). These are like the “attractor valleys” of Stuart Kauffman, which can correct errors in copying occurring in some constituent cycles, unless they are overwhelming (catastrophic).

For RNA (retro-) viruses, a large rate of mutation is still favourable, because it facilitates their evasion of the host’s immune system. If, like HIV, they then attack the host’s immune system directly, they are rapidly fatal to the host. This, however, ceases to be favourable to the virus, unless it achieved transmission to another host (by infection) before the death of the first host.

In any case, the change of the genetic template from RNA to the more stable DNA (error rate 1 in 100 million) decreased the error rate and increased stability. While in the RNA world we could hardly speak of a stable species (HIV has innumerable varieties), in the DNA world we are closer to being able to do so. However, even bacteria, who are DNA-operated prokaryotes, gene swapping between species often occurs, making the dividing lines between species fuzzy. We have genetic networks, rather than family trees.

Eukaryotes have a still greater degree of stability, especially with the invention of sexual reproduction, which even the lowly yeast cell achieved, among others. This was further specialized in multicellular organisms – the transition to this state passing through intermediates like slime molds and sponges. In plants there is also the transition in the adult stage from the 1N to the 2N (haploid to diploid) condition, from fungi to mosses to ferns to seed plants.

All these are steps from variability to stability. Species became stable and persistent. However, along with flexibility which variation facilitates, other properties were lost; rapid adaptability to a changing environment, rapid evolutionary change in general, and, in particular, the ability to regenerate a lost limb, or even a head (in worms). A sponge can reassemble itself even when passed through a sieve. So which way lies progress? It depends on how quickly the environment is changing, or apt to change in the future.

It is the old question also relevant to human society: is it better to be conservative, i.e. conserving previously attained values which had proved themselves to be useful in the past, or to be radical, rapidly seeking new alternatives to established ossified structures, i.e. exploring new option space? It depends on how fast society and technology is changing, and apt to change – which, however, in turn depends on the mix of conservative/radical attitudes in the society. A hypercycle?