Sticking a fork in Natural Selection (Introduction)

by xeno6696 , Sonoran Desert, Sunday, December 11, 2011, 18:02 (4709 days ago) @ dhw

dhw:

Round we go. ... Now you are arguing that it wasn’t by chance but by need. You really can’t have it both ways – either this was a random mutation (your original argument) or it was an adaptation required by the environment.

Not quite... you missing some detail here. In the experiment, the bacteria without the lactamase gene was in an environment where it could still engage in pyrolysis. Analysis of the genes over generations demonstrated that in the case for the bacteria, random combinations of their genome ultimately culminated in one group gaining an ability to digest lactose. In the case of the bacteria (and this was the only case in question at the time I posted it) this was a novel mechanism created purely by chance. The bacteria were not in stressed conditions--They couldn't be. Bacteria - lactamase gene = Bacteria that "never knew what it was missing." It's beyond scope here, but there are a series of skeptical questions you can ask about this experiment, but we can save those for later.

I don't have the time to dig for old posts, but clearly even in my wording you grabbed above, I was only talking about one species, clearly isolated and in a laboratory. The context of the original post I DO remember, was in the paraphrased assertion (by you or David) that random processes can't generate anything. My post you quoted from above was to counter THAT claim. Also, the selection event in the case of the bacteria was when it was introduced into a lactose-rich medium with non-lactamase species and it dominated in terms of population. No selection ocurred in the laboratory until THAT happened.

I have also *never* asserted that evolution was a purely random phenomenon. I remember posting some quotes from a Massimo Pigliucci book that was arguing precisely the opposite--that the only alternative to design was a purely random process.

MATT: I keep getting tripped up in Natural Selection discussions, partially because I always lose sight of the fact: Evolution by Natural Selection works ONLY on a demand basis... the organism comes under stress and then the organism adapts... again I ask, why is there some need to assume that need doesn't precipitate change?

When have I ever argued that need doesn’t precipitate change? That is the whole point of adaptation! But your confusion over the beta-lactamase experiment highlights the issue of what causes change. One cause is the need to adapt, and the other is random mutation. Nobody knows to what extent these two causes overlap. All we know is that if the changes do not enable the organism to survive in the given environment, Natural Selection will result in its being eliminated.

In the lactamase example, there wasn't a clear "demand" for the function. Maybe this is your suggestion? That evolution isn't purely a demand-driven enterprise? It's plausible but it's a hard case to make.

MATT: Both yourself and David have chastised me about the idea of currently accepted evolutionary theory as not "being fast enough."

... NS does not motivate anything. Changes in the environment may well be the prime motivator, because organisms must ADAPT or die, but random mutations are the other motivator and may account for INNOVATIONS (new organs). But again these will not survive unless they are useful in the given environment. NS does not MOTIVATE either form of change – it only determines whether these changes will survive. It is passive (David’s term, not mine) in the sense that it doesn’t create anything. It only works on what already exists. The argument concerning the SPEED of evolution has nothing to do with NS. David’s point is that the speed is too great for chance to have created this vast variety of organs and organisms in the given amount of time.

What is a selection event, and what is the result of a selection event? What is a selection event's relationship to Natural Selection?

My answer: Natural selection we have previously agreed is a filter that weeds out the unfit. Is it not true that a selection event is the beginning of the process that culminates in what comes out of the filter? I answer yes.

An organism (as in the lactamase example) will collect all benign changes over time--BUT until something happens in the environment (selection event) there is no change to record.

Your answer: ????

Summary: NS does not create anything. Random mutations may be creative. NS does not motivate anything. Changes in the environment motivate changes in the organism (= adaptation). NS decides which changes – by random mutation or adaptation– will survive. Nothing can be selected, even by Nature, before there is something to select.
QED, LOL, DHW

Perspectivism. NS IS responsible for what we see!
No event-->no selection-->no observed change in an organism.
The species is in stasis.
Event-->selection-->observed change in an organism.

The species has become "something else."

Who's laughing now?

--
\"Why is it, Master, that ascetics fight with ascetics?\"

\"It is, brahmin, because of attachment to views, adherence to views, fixation on views, addiction to views, obsession with views, holding firmly to views that ascetics fight with ascetics.\"