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why do we die?

Jonah Thomas JEThomas at ix.netcom.com
Mon Nov 13 06:53:59 EST 1995


In <4803b3$amr at nntp3.u.washington.edu> 
mkkuhner at phylo.genetics.washington.edu (Mary K. Kuhner) writes: 

>jcooper at acs6.acs.ucalgary.ca (jason cooper) writes:

>>It's advantageous for *you* to live a long time, but is it
>>advantageous to the species?  I would guess that it is, at best,
>>neutral, and at worst very detrimental.

>This would make it very hard to understand the widespread success of
>trees, most of which live for decades or centuries after first
>reproduction.  Almost nothing is always advantageous or always
>disadvantageous; it depends on circumstances.  I suspect trees profit
>from long lifespans because the survival of very young trees is so iffy;
>one bad winter or forest fire can wipe out all the young individuals.
>Survival of the older individuals provides a way of restocking after
>such a disaster.

Also, trees are very good at sequestering resources.  They can shade out 
anything shorter (except things that can handle the light the trees 
don't use) and their large root systems can take up a lot of water and 
minerals.  They can drop leaves on shorter plants and damage them that 
way.  Some trees make poisons that inhibit other plants, and when you're 
a _tree_ you can make a lot of poison.  I have the idea that walnuts 
particularly use their nuts as weapons -- anything brittle that lives 
too near a walnut tree will be smashed.  (I thought of this from having 
a walnut tree too close to my house, that makes it an obvious idea, like 
Newton and the apple but more so.)

Even if it turns out that trees are dinosaur-like, that they can't 
evolve as quickly because of their population structures, still they've 
done the particular things that let them outcompete better species.  
They're the IBMs and the MicroSofts of the plant world.

>The organism that really puzzles me in this context is the century plant
>(which I was lucky enough to see flowering once in Berkeley,
>California).  It lives longer than I'm likely to, and flowers *once* at
>the end of its lifespan.  As far as I know it doesn't propagate
>vegetatively, either.  What conditions make this a reasonable life
>history?

I dunno.  




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