Sticking a fork in Natural Selection (Introduction)

by dhw, Sunday, December 11, 2011, 23:20 (4709 days ago) @ xeno6696

These posts are getting messy. Let’s deal with the beta-lactamase experiment first. On 27 July it was a random mutation; on 10 December the cells were under stress and responded by “inventing” the ability to metabolise lactase (adaptation); on 11 December they were not under stress and created a novel mechanism by chance. You now say there was a random mutation, but
“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.” Followed by: “[...]until something happens in the environment (selection event) there is no change to record. Your answer: ????

My answer is that the change was the random mutation, but since the new form was in isolation, no selection occurred till the two “species” were put together. Then the new organism dominated. A classic case of Darwinian evolution: a chance mutation gives one form an advantage over another when they are in competition, and natural selection ensures that the species more suited to the environment flourishes. NS selects from EXISTING organisms; it doesn't create them. More about “selection event” in a moment.

Briefly: I’ve never claimed that random processes can’t generate anything. Change is caused by adaptation and random mutations, but we don’t know to what extent they overlap. And: MATT: “I have also *never* asserted that evolution was a purely random process.” I have *never* asserted that you did.

MATT: The key to my thinking (and why I've been stubbing my toes with you and dhw) is that I don't see how we can say Natural Selection isn't the driving force of evolution when we agree that:
1. We have a "demand-based" evolutionary system. 2. The cause of the demand are called "selection events." 3. A species (viewed as a group) changes in response to the selection events.

One of the causes of confusion is your continual shifting of ground. Now we have two vague new terms. I accept “demand-based” as meaning that survival demands suitability to an environment.

MATT: 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. [Three cheers from David and me!] 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.
So do I, but why call it a “selection event”? Why not call it an environmental change? Here is the process: 1) environmental change, 2) adaptation (maybe useful mutation), 3) NS (the filter). Organisms won’t adapt until this “event” (environmental change) takes place. So how can the final filtering stage be the driving force or “primary cause”? The driving force is the need for organisms to cope with the environment. NS determines which will succeed. I hope you’re not pretending the term “selection event” is synonymous with Natural Selection!

MATT: I don't see how it makes any difference that epigenetics or random mutation are functions that create the genetic variation when we have a pretty clear image of cause-and-effect in my mind. Does this make my confusion a little more clear?

I agree that whether these changes are due to epigenetics or random mutations makes no difference to the sequence of cause and effect, as described above. WE do not have a pretty clear image of cause-and-effect in YOUR mind, but the source of your confusion is clear to me: you think the effect – NS deciding which changes will survive – takes place before the cause – new environmental conditions or random mutations bringing about the changes from which Natural Selection will select.

MATT: Perspectivism. NS IS responsible for what we see!

Yes, because NS has ensured that we see the species that were best suited to survival. That doesn’t make it the driving force that CREATES the new species.

MATT: No event-->no selection-->no observed change in an organism.
The species is in stasis.
Event-->selection-->observed change in an organism.

Wrong order: event – change in organism – selection - what we see. There can't be selection till there's something to select from! Your event (environmental change) may cause the changes that Natural Selection will select or reject.

MATT: The species has become "something else."
Agreed.

MATT: Who's laughing now?
Not laughing. Screaming.

MATT: As an aside--I know no other place to put this--I'm starting to think that the distinctions we make between species is in many cases spurious... it seems to me that they are as arbitrary as the borders on a map.

As I mentioned in my post of 10 December at 07.54 (very early for me!), Tony and Charles Darwin raised the same problem on many occasions.