Sherlock Holmes wrote: ↑Wed Feb 23, 2022 10:35 am
I was reading
this article earlier, in there we read:
To better understand the impact of this situation, think of it this way: With a genome size of 2.8 × 10^6 and a mutation rate of 1 mutation per 10^10 base pairs, it would take a single bacterium 30 hours to grow into a population in which every single base pair in the genome will have mutated not once, but 30 times! Thus, any individual mutation that could theoretically occur in the bacteria will have occurred somewhere in that population—in just over a day.
This seems to be an admission that even if
every possible mutation (from the finite set of possibilities) occurs at some point in the colony, then we still have -
bacteria, surely with these rates of reproduction and probabilities of mutation and so on, doesn't this show that the bacteria evolving never leads to anything other than a variant of the bacteria? That the set of all possible mutants is either dead or still more or less the same bacteria.
Your analysis of their statement is flawed in two ways.
First, "every base pair will have mutated" is referring to point mutations only. The set of all possible insertions of arbitrary size is necessarily many orders of magnitude larger. Even if we limit it to sequence duplications that preserve the RNA reading frame (which aren't the only type of
de novo insertion), the space of all possible, arbitrary-length insertions is larger by many orders of magnitude.
Second, your analysis conflates every single mutation happening somewhere with every combination of those mutations either appearing or collecting somewhere. Even if we were to posit that some collection of point mutations would render the resulting organism as something other than a bacteria, the probability that such a collection would come together in one individual is much, much lower than the probability that they appear independently in separate organisms.
Sherlock Holmes wrote: ↑Wed Feb 23, 2022 10:35 amGiven the rate at which bacteria reproduce and their number on earth and in societies, shouldn't we see evidence that the genome has developed more and more novelty? yet it seems all we see is just bacteria...
Whether it's intentional or not, you've just made a circular argument. We
do see much more than bacteria and see all kinds of what would potentially be transitional forms. There are prokaryotes of varying complexity, single-celled eukaryotes, eukaryote colonies of undifferentiated cells (
Volvox spp., for example), and true multicellular organisms. Each of those loose categories displays a wide range of complexities.
We also have evidence that the events resulting in eukaryotes are a form of symbiosis. We can identify the closest living relatives of the bacteria that became chloroplasts and mitochondria. An interesting read is
this paper in Nature that discusses the genetic similarities between eukaryote mitochondria and the
Rickettsia genus of bacterial parasite. The data imply not only that bacteria had already widely radiated at the time that eukaryotes acquired mitochondria, but that the common ancestor of mitochondria and
Rickettsia spp. was already an obligate parasite.
We further have evidence that such "organelle capture" events happened multiple times. The chloroplasts in green plants are genetically and physiologically similar to prokaryote cyanobacteria, but there is an interesting group of algae (known as "red algae") with chloroplasts that were originally eukaryotes. Their choloroplasts are nucleated and have their own membrane-bound organelles, the markers of eukaryotic cells.
You may make the counterclaim that this is some sort of "creationist orchard" in which there is some arbitrary category distinction that can't be crossed, but the diversity of life is real and matches what we would expect of evolution beginning with prokaryotes. Instead of evolution having to explain why bacteria only remain bacteria, creationists have to explain apparent events that resulted in ancient examples of archaea and bacteria merging into what is now recognized as a completely different domain of life.
Sherlock Holmes wrote: ↑Wed Feb 23, 2022 10:35 amSo is there evidence that bacteria can become something quite different given enough time
Oh, yes.
Sherlock Holmes wrote: ↑Wed Feb 23, 2022 10:35 amand if not, why not? are the possible states that the genome can get into simply insufficient to ever lead to escalating novelty?