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Author Topic:   Disabling Bacterial Resistance
PaulK
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Posts: 17179
Joined: 01-10-2003


Message 22 of 60 (216834)
06-14-2005 3:34 PM
Reply to: Message 19 by mike the wiz
06-14-2005 8:48 AM


Re: Mikey's catch 22
There is no "Catch 22", just a false dilemma.

The underlying assumption is that either the species will die out in a relatively short time (no more than a few centuries) or it will be so well adapted that no evolutionary change is likely.

However this is not the case.

Even in a highly stable environment the fitness could be arbitrarily close to 1 . If it was a very little below 1 then the population would only decline very slowly, giving time for speciation.

But real environments often include short term variations like bad weather. A species that would otherwise hang on can be wiped out by a run of bad luck. If that required conditions that were expected to happen once in 2,000 years then on average the species wuld last 1,000 years - long enough to evolve into a new species which could better survive.

And we are not restricted to short-term variations. Environments can change over time. If the change is slow enough then a species which would otherwise die out can evolve to "track" the change. Examples include so-called "arms races" where predator and prey each drive the evolution of the other. As the predator improves it's ability to catch the prey, the prey is driven to evolve ways of better evading capture - and vice-versa.


This message is a reply to:
 Message 19 by mike the wiz, posted 06-14-2005 8:48 AM mike the wiz has replied

Replies to this message:
 Message 27 by mike the wiz, posted 06-14-2005 8:20 PM PaulK has replied

  
PaulK
Member
Posts: 17179
Joined: 01-10-2003


Message 34 of 60 (217034)
06-15-2005 2:26 AM
Reply to: Message 27 by mike the wiz
06-14-2005 8:20 PM


Re: Mikey's catch 22
Well we can add another erroenous assumption to Mikey's catch 22. It assumes that evolution DOESN'T happen slowly. If speciation happens in 1,000 years that only means that it takes 1000 years for enough change to accumulate for it to be called a new species. Not that it suddenly changes into a new species.

Environmental change drives evolution because it changes the relative contribution to fitness of the variations with the species. Thus if an ape moves into an environment where intelligence becomes more important then natural selection will tend to make that trait more common - and if mutations leading to higher intelligence still occur natural selection will favour those, also.

This is exactly the same principle as bacterial resistance. Put bacteria into an environment where an antibiotic is common and you create selection for resistance. Make the dose too high on a population containing no resistant bacteria and they will die out. Make it low enough and the bacteria will hang around long enough for some to acquire resistance by mutation and those will spread. Thus Mikey's "catch-22" is refuted by the subject of the thread since it requires that bacteria could never evolve resistance to antibiotics.


This message is a reply to:
 Message 27 by mike the wiz, posted 06-14-2005 8:20 PM mike the wiz has replied

Replies to this message:
 Message 35 by mike the wiz, posted 06-15-2005 7:57 AM PaulK has replied

  
PaulK
Member
Posts: 17179
Joined: 01-10-2003


Message 36 of 60 (217066)
06-15-2005 8:22 AM
Reply to: Message 35 by mike the wiz
06-15-2005 7:57 AM


Re: Shraff, talk to me
quote:

There's a lot of problems with this logically.

Firstly, if an ape moved into an environment where a standard of intelligence is needed then it would not survuve without that standard, otherwise it wouldn't need it.


Mike that is not a logical problem with my point - it's not even a problem. I am not discussing the situation where increased intelligence is necessary from the start.

quote:

How long would it take an ape to get a human brain? Or even extra intelligence capabilities? No significant change in animals has been observed in thousands of years time period.

For the first question we can do beter - we have good estimates for how long it DID take. All you need to do is to adequately define your start and end points.

For the latter we do not have thousands of years worth of observations. Major changes would typically take a number of speciations, often interspersed with long periods of stasis. Thus even if we had such records (and we would need detailed records of every species as it was thousands of years ago) we wouldn't expect to see major changes.

quote:

That means that mikey ape will wait a long long time, so if he survives that long long time, then he wouldn't need the intelligence anyway, because he's survived.


Then it's a good job that my example says that it is NOT absolutely necessary, isn't it ?

So one problem is in error and the other two do not deal with the argument as I stated it. None of them represent genuine problems and your "catch 22" is still refuted.


This message is a reply to:
 Message 35 by mike the wiz, posted 06-15-2005 7:57 AM mike the wiz has not replied

  
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