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Re: dinosaur copulation?

derek@nezsdc.fujitsu.co.nz writes:
>Humans have not _evolved_ into this situation.  It has been brought about 
>by both an extended family where the old are cared for and by advances 
>in nutrition and public health.  The natural life span of a human in 
>either a jungle or other similar environment is around 40 to 50 years, 
>which corresponds remarkably closely to the reproductive life span
>of females.

Yet our animal pets, whose lifespans are increased by an even vaster
amount over their wild counterparts than humans mere doubling of lifespan,
suffer no such selective aging effects.  Why should the reproductive system
of humans alone have evolved to just so much longevity and no more?

In point of fact, the "natural" lifespan of humans is in that range in part
because of the dangers of childbearing.  Menopause results in a jump in life
expectancy even today, it was far greater before medicine reduced the risks
of bearing children to today's levels.  The average may have been 40 or 50
years, but old women in particular lived well into their 60's and 70's if
they survived their child-bearing years.  Something more is at work here.

>This looks much more like social and economic change than any evolutionary 

Evolution is driven by any sort of environmental factor.

>I would expect that preagricultural societies would have life expectancies in
>the late thirties.

Practically every one of Jane Goodall's chimps that survive childhood can
better that.  Averages are misleading, they are reporting all kinds of death,
accidental and otherwise, not the "natural" lifespan of creatures.  Death by
whooping cough may be "natural" but it tells you nothing of what person would
have reached "naturally" if they had been less unlucky in childhood.

>The historical evidence suggests that women essentially continued having 
>babies until they died and that other members of the group then looked 
>after them.

And in years of reading anthropological texts I've never seen this assertion
until now.  You are reading far too much into your math, methinks.  You need
to eliminate _luck_ from your averages before it will tell you anything about

Larry Smith