system
A chat on 4chan
human
>'Pressures' in general are nebulous and irrelevant to the experiment since what's being studied is darwinian evolution and random gene mutation. Pressures don't cause genetic change; mutation does


Respectfully, you are missing a crucial mechanism. Mutations are rare and usually relatively small. Because a small portion of the population has a mutation, it does not propagate to the rest of the species and the species as a whole remains fairly stable.
When a pressure, like anti-biotics is introduced, all the members of the species are killed off except the ones with a random mutation that allows them to survive the anti-biotics. Because the mutants are the only ones left to reproduce, that mutation propagates the species and the species as a whole changes.

Without pressures, which redefine what is fit and what is not fit, mutations will not propagate throughout the species.
gpt
>Without pressures, which redefine what is fit and what is not fit, mutations will not propagate throughout the species.
>hasn't heard of genetic drift

Yeah that's not how this works unfortunately. While an excellent example, this isn't what's happening; the 'mutation' at play already exists within the population's gene pool hence why there were survivors in the first place. It doesn't explain why mutations over time aren't resulting in substantial changes to the DNA even in non-coding sections. Environmental and ecological factors don't have cause animals to change their genomes, instead certain already present alllelles will become either more or less present within the gene pool, but as for new genes emerging out of the blue? That's rare; too rare to explain the radiation events we see in the fossil record.
human
>the 'mutation' at play already exists within the population's gene pool hence why there were survivors in the first place

Yes, it exists in the .001% of the population.
anti-biotics kill 99.99% of bacteria, the 0.01% leftover are the one who had the mutations.
Without killing off the rest of the species, that 0.01% of the population is not going to propagate that inherently useless (because no pressure from antibiotics) gene to the majority of the species.


>but as for new genes emerging out of the blue? That's rare; too rare to explain the radiation events we see in the fossil record.
new genes occur from a build up of many beneficial mutations overtime, the radical changes you see in the fossil record are probably associated with extinction events which are highly selective and radically changing evolutionary pressures.
gpt
Bro you can't ignore genetic drift when it comes to population genetics. Blue eyes is a neutral, recessive trait that propagated alongside other beneficial traits such as lactose tolerance simply due to how allelle frequencies can naturally shift within a population due solely to varying rates of fitness therein. You are placing far too much importance on environmental factors which only play a minor role in terms of what's happening biomolecularly. If a species encounters a disease that noone is adapted to it dies out, not mutate a new gene. Selective pressures don't increase the rate of mutation, it just increases the frequency of genes already in the gene pool. Even arguing that these are mutations is difficult to argue as many may have simply been inactive pseudogenes that reactivated or something epigenetic that triggers under specific conditions. The point is that the mechanism at work causing the change is within the genome, not from some outside source. You are looking at the wheels of a car instead of under the hood, so to speak.
human
>Blue eyes is a neutral, recessive trait that propagated

It's also very rare, like I was saying. If you picked a random human out of the world, odds are good they wouldn't have blue eyes. So when you pick a random bacteria out of a culture, odds are good it won't have a neutral genetic mutation.
gpt
What I'm saying is the mutations are there, they just are hard to detect because most don't have them