Re: Cornering the causes of aging

From: John Clark (
Date: Tue Jul 11 2000 - 08:26:15 MDT

Damien Broderick <> Wrote:

>puppy dogs and pussy cats have ample frequent litters, while humans
>tend only to have singletons

The vast majority of species put their resources into having a large number
of offspring. A small number of species, such as humans, have only a few
offspring but considerable resources are used to ensure that they actually
make it into adulthood. In both strategies enormous energies are put into
reproduction and that's a much better investment from evolution's point of
view than immortality.

>It needs to show exactly why different critters sharing the same indices
>can vary in lifespan by huge ratios - 1:10, etc.

I once saw a plot of average body weight Vs average life expectancy of several
hundred species, with one glaring exception it fit a straight line pretty well,
usually the larger the species the longer it lived. Humans however were completely
off the chart, they lived 4 or 5 times as long as you'd expect given their size.
I've also heard that most mammals have about an equal number of heartbeats
during their lifetime because small hearts beat faster, but human hearts beat many
more times than any other animal. Evolution probably let us live longer because our
children are helpless for such a long time. And that probably happens because
it takes a long time to learn how to use that big brain effectively, for that matter it
takes a long time to even get a big brain, due to the small size of the birth canal,
caused by bipedalism, the brain has a lot of growing to do after birth.

                      John K Clark

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