Evolution and complexity

No need to try to get your head around that level of incomprehensibility. There is a mind-boggling statistic closer to home. It is that the bacteria in and on your body outnumber your own body cells ten to one.Mirroring the point that to the first approximation, all species are extinct (99.9% of all there’s ever been), we can also say that to the first, and probably the second and third, approximation, all organisms on earth are microscopic.Cheers, DT

It’s also worth noting that, where it offers a survival advantage, simplicity is just as merrily adopted. The obvious example is Sacculina barnacles. Barnacles are arthropods -- fairly ‘advanced’ critters with a hard exoskeleton. Yet Sacculina adults are little more than jelly-like blobby endoparasites of crabs, resembling with their root system that spreads through the crab some sort of simple plant. See eg here. Only in their larval stage is their arthropod affinity apparent. Compared to ‘normal’ barnacles, they are very simplified.Is a two-legged creature ‘simpler’ than a four-legged one? I’d have thought so -- it’s got fewer parts. Yet cetaceans have lost their back legs through evolution, and snakes, caecilians, amphisbaeneans and so on have lost all four limbs. Evolution will go for simplicity too: there’s no inevitable climb to greater complexity.Cheers, DT