From: williamsk@gtephx.UUCP (Kevin W. Williams)
Subject: Re: Restricted breeding (was Re: The Moat around God's Eye)
Organization: gte
Date: Tue, 28 Jul 1992 17:11:56 GMT

In article <742@tdat.teradata.COM>, swf@teradata.com (Stanley Friesen) writes:
> In article <1992Jul25.102521.10398@techbook.com> szabo@techbook.com (Nick Szabo) writes:
> |In article <726@tdat.teradata.COM> swf@tdat.teradata.com (Stanley Friesen) writes:
> |
> |>If there is a crash, then *everyones* offspring are at risk,
> |
> |But each individual offspring is at equal risk.  The rabbit which had
> |10 bunnies, perhaps helping to cause the crash, will have 10 times
> |the chance of offspring surviving the crash than the rabbit which,
> 
> Not necessarily true.  As long as each parent has about the same territory,
> than the one with the larger litter during times of shortage will most 
> likely lose *all* of them, but the one with the smaller litter will succeed
> in raising a few. (Remember, with equal parental territories, essentially
> the same amount of resources must be allocated amoung the whole set of young
> - this is why most animals have a variable clutch size strategy, often
> accomplished by favoring one child, so that in times of trouble that
> one can be kept alive, by sacrificing the others).
> 
> 
> An interesting for instance - in humans starvation surpresses ovulation.
> Thus reproductive rates are kept in line with available resources.
> |in a fit of ecological correctness :-), restricted itself to one
> |offspring.  Genes for "ecological correctness" will be eliminated.
> |
> |
> |-- 
> |szabo@techbook.COM  Public Access User --- Not affiliated with TECHbooks
> |Public Access UNIX and Internet at (503) 644-8135 (1200/2400, N81) 
> 
> 
> -- 
> sarima@teradata.com			(formerly tdatirv!sarima)
>   or
> Stanley.Friesen@ElSegundoCA.ncr.com

This concept applies across larger population groups as well. Remember
that most animal occur in population pockets, with only limited breeding
and intermixing across pockets. For the sake of argument, let's look at
the hypothetical Zog. The Zog normally uses unrestricted breeding. A mutation
arises in one individual which causes it to restrict its breeding at 80% of
crash point. Assume, as well, that we are dealing with two pockets which have
crashed at about the same time, and live in environments where they are
able to support about the same population. Assume, as well, that the populations
do slowly intermix, that the boundary between them is a soft one (i.e., tree
dwelling squirels are unlikely to cross an open plain between two forests, but
can and will given sufficient incentive).

The pocket with the mutation will, after several generations, have the mutation
spread throughout the population. Assuming that the mutation is recessive (
a reasonable assumption), then 25% of the population will restrict breeding,
and 50% more will carry the unexpressed recessive. Now, as our two pockets
grow, the pocket with the mutation will marginally slow down its crash vs.
the other. If they pull off even one generation, what's the result? They
are able to displace the other population following its crash. The result:
the conservative group won, just by holding out a little larger. Really
attractive things start to happen when the population that takes over the
recently crashed area is double-recessive. This population will restrict
more thoroughly, allowing it to outlive more prolific pockets, and invade
more territory. Eventually, the conservative population will win out.

Kevin Wayne Williams
     UUCP : ...!ames!ncar!noao!asuvax!gtephx!williamsk

               Remember : Brute force has an elegance all its own.
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