[UA] Crosswords and Blue Teets

[James McGraw]

>>> menzi212 at yahoo.com 06/07/01 09:14pm >>>

I'm sorry, but this post is rather long and horribly off-topic.
To save myself from the wrath of Matthew Norwood, I've put an (incredibly feeble) ObUA at the bottom, though. :-)

---- James McGraw pdytjem at nottingham.ac.uk wrote:
>
>> Not true. Adaptations that confer even a small 
>> change in fitness can spread throughout a 
>> population surprisingly quickly. An adaptation 
>> such as this would actually be a significant 
>> enough advantage that it would spread through 
>> the population extremely quickly.
>
>     You are talking about learned behavior, not
>instincts.

Actually, I am talking about instincts.

<snip>
>     When the first blue tit bottle-opener opened its
>first bottle of cream, you might say "Look a
>beneficial mutation in its feeding instincts" instead
>of "Finally got around to trying that on the bottles,
>eh?" 

That's what I _was_ saying.

> That might be a decent explanation, exept that,
>if it was an mutation of their instincts, other blue
>tits would not have done it too.  It would have been
>restricted to that particular tit's children.
>
>     Now, the species was doing fine without opening
>bottles, so the behavior is only a minor or negligible
>advantage in terms of staying alive - the only terms
>that count for Darwinian evolution.  There was no
>great evolutionary pressure (eg: lack of other food)
>that would cause the non-mutant population die off and
>only allow the "mutant instinct" blue tits would
>remain.

This is the point that I took issue with. A genetic trait, such as the novel behaviour of milk-bottle opening, that confers an advantage to the organism possessing it (and what is important here is its benefit to the individual organism compared to the rest of its species) will spread in a population. There is no need for there to be an especially great selection pressure on the species (such as widespread food shortage). This is simply because the life of a blue tit is quite hazardous enough even under "normal" conditions (the average blue tit lays 7-8 eggs per clutch. If all of these young survived to reproduce, we'd soon be knee-deep in blue tits). The normal rigours of daily life are enough to weed out the less fit blue tits, so that only the fittest survive to reproduce. Those blue tits with an "edge" (eg those who can exploit a new food source such as the tops of milk bottles) have a greater chance of survival to an age at which they can reproduce, so the gene spreads in!
 the population. The rate at which genes spread through populations can often be surprisingly high (as in the aforementioned blackcaps).

Of course, whether or not this is actually the case with blue tits is another question entirely. Further study is probably needed to find out whether the selective advantage is actually great enough to produce a significant rise in the number of blue tits showing this behaviour in such a small time. My point is simply that it is entirely possible for changes to occur in the genetic make-up of a population without the need to invoke extremely adverse conditions (also, it is possible that only some blue tits may display this behaviour, ie the gene may not have spread entirely throughout the population).

ObUA: Hmmm.. <racks brains> I suppose you could say that life as a bluetit is almost as tough as life in the OU... only those with the ability to peck the tops off milk-bottles can survive. Oh, well, I told you it was feeble. :-)

james the cat

"In science it often happens that scientists say, 'You know that's a
really good argument; my position is mistaken,' and then they actually
change their minds and you never hear that old view from them again.  They
really do it.  It doesn't happen as often as it should, because scientists
are human and change is sometimes painful.  But it happens every day.  I
cannot recall the last time something like that happened in politics or
religion." 
                -- Carl Sagan, 1987 CSICOP keynote address



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