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From: JAHAYES@MIAMIU.BITNET (Josh Hayes)
Newsgroups: sci.bio
Subject: Re: human lifespan and evolution
Message-ID: <90304.100534JAHAYES@MIAMIU.BITNET>
Date: 31 Oct 90 15:05:33 GMT
References: <1990Oct28.120050.7521@newcastle.ac.uk> <1990Oct29.000540.6280@midway.uchicago.edu>
Organization: Miami University - Academic Computer Service
Lines: 43

In article <1990Oct29.000540.6280@midway.uchicago.edu>, chi9@quads.uchicago.edu
(Lucius Chiaraviglio) says:
>
>In article <1990Oct28.120050.7521@newcastle.ac.uk> W.P.Coyne@newcastle.ac.uk
>writes:
>>Suppose the people in a communtiy delated having chlidren until as late
>>in life as possible (but not so late that the population declined because
>>of too few births).
>>Could this cause the average lifespan to increase by several decades, if
>>they continued this over tens of generations?
>
>        A similar experiment has been done in the fruit fly Drosophila
>melanogaster.  The conceptual difference between this experiment and what you
>propose is that instead of directly getting the flies to delay reproduction,
>those flies capable of reproducing late were selected by transferring to new
>vials only those offspring produced late in the life of the flies.  After
>several generations of this, the selected flies were noticeably slower to
>reproduce and lived substantially longer -- I think both effects were in the
>lower tens of percent, but I can't remember the exact numbers.  Lower tens of
>percent would correspond to a couple of decades longer life for us.
 
But this presupposes that there exists genetic variation for both
delayed reproduction and delayed senescence, and that the two traits
are linked. There probably is no such variance.
 
And do you refer to males and females? How long do males have to
wait; after all, some men long past 70 can still father children;
few women past 45 can carry a pregnancy to term successfully. The
fact is, people are usually long done with reproduction before
senescence becomes an issue. If we force people to wait until, say,
40 to have children, they'll still be well done with child-bearing
by the time they're 50, and expected life span these days in the
U.S. is what? About 75 years? You posit a linkage that delayed
reproduction that is still successful is a genetic trait that is
linked to longer lifespan. Forcing everyone to delay vitiates the
genetic component of the former, and the linkage is completely
unsupported. Even as an intellectual argument, I don't think it works.
 
Josh Hayes, Zoology Department, Miami University, Oxford OH 45056
voice: 513-529-1679      fax: 513-529-6900
jahayes@miamiu.bitnet, or jahayes@miamiu.acs.muohio.edu
"Ain't nothin' worth nothin' that ain't no trouble."
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