From: swf@teradata.com (Stanley Friesen)
Newsgroups: rec.arts.sf.written
Subject: Re: Restricted breeding (was Re: The Moat around God's Eye)
Date: 28 Jul 92 01:15:25 GMT
Reply-To: swf@tdat.teradata.com (Stanley Friesen)
Organization: NCR Teradata Database Business Unit

In article <1992Jul24.070151.11069@oracle.us.oracle.com> mfriedma@uucp (Michael Friedman) writes:
|In article <726@tdat.teradata.COM> swf@tdat.teradata.com (Stanley Friesen) writes:
|>|1.  Don't have kids when we're crowded so that my species doesn't have
|>|a boom and bust. 
|
|>|2.  Don't have kids when we're crowded because I can more relibably
|>|propagate my genes if I wait until we have more room.
|
|>|Do you understnad the difference between these goals?
|
|>Yes, but I maintain that in the long run they amount to the same thing.
|>To achieve 2 effectively requires or entails achieving 1.
|
|Not at all.  The degree of crowding necessary to make having children
|a bad idea may be greater than the degree of crowding necessary to
|have a bust.  The smaller the investment per child the more likely
|this is to be true.

Yep, and if this is so then the genes for smaller clutch size will spread,
the population will stabilize as fecundity drops, and the bust will
have been avoided.   Achieving 2 entails(implies) achieving 1.

This scenario is why I said "require *or* entails".

|>If there is a crash, then *everyones* offspring are at risk, and no
|>lineage is exempt for elimination, so a population that is prone to
|>periodic major crashes is bad for *each* *individual*.
|
|You miss two major points.  Your mechanism - reason 1 - has not
|sanction for cheaters.  Mine, reason 2, does.

I think the main issue is really that you are using a much more restrictive
definition of 'purpose' than I am.  I do not require that 1) be the
*direct* cause of the result, only that it be a related factor.
(In a technical paper I would probably tend to be more precise, but that
seems to be unnecessary in this sort of forum).

My main point is not precisely about *causation* as about results.
The two *effects* are tied together, and when one occurs so does the
other.

|Your mechanism can't work because once reason 2 comes into play busts
|can't happen any more.  If an event never happens how can it put
|evolutionary pressure on a species?

That was part of my point.  You can't have one without the other.
Thus, from a *practical* point of view, using *colloquial* English,
the two are equivalent *in* *practice*.  As far as what we are talking
about here is concerned trying to make this sort of fine distinction
is really over-fastidious.  (Now, in a life-history study, for a refereed
journal, things would be different, and I would take care to express
things more precisely - but then I would likely use mathematics, with
only a little bit of English).

|>[r-strategists get around this by dispursing a significant portion of thier
|>offspring out of the immediate area, and hopefully out of the range of
|>the inevitable population crash, that is what makes them "weeds"].
|
|True for some, but not others.  Look, for example, at a predator-prey
|system.  Because it is so tough to predict future populations
|predators oftne can't tell when breeding is a bad idea and starvation
|and population busts are common.

Most preadators I know of in detail tend to use the 'keep a spare' approach
to children, they start by producing more than they expect to be able
to support, and then lavish more attention on the few that they can actually
support.  If they have a boom year, well then they manage to feed all of
them, but in most years the smaller, less favored ones die (unless an accident
or predation kills one of the favored, in which case there is a "spare"
to take its place).

This is called a compromise strategy, and is quite common.



By the way, I have just started reading a new book on the evolution of
life history strategies that seems to be fairly understandable even
without much technical background (despite lots of math).  It is:

	"The Evolution of Life Histories"
	 by Stephen C. Stearns

So far it seems to be a fairly good, balanced treatment (and thus a
good antidote to "The Selfish Gene").
-- 
sarima@teradata.com			(formerly tdatirv!sarima)
  or
Stanley.Friesen@ElSegundoCA.ncr.com