[ExI] Are Limited Lifespans An Evolutionary Adaptation?

[rex]

Rafal Smigrodzki <rafal.smigrodzki at gmail.com> [2015-06-18 16:43]:
>    On Tue, Jun 16, 2015 at 7:13 AM, BillK <[1]pharos at gmail.com> wrote:
> 
>      Are Limited Lifespans An Evolutionary Adaptation?
>      George Dvorsky   6/12/15
> 
      http://io9.com/are-limited-lifespans-an-evolutionary-adaptation-1710634703
> 
>      Quotes:
>      By running variations of their model hundreds of thousands of times, a
>      research team led by Yaneer Bar-Yam from the New England Complex
>      Systems Institute (NECSI), in collaboration with the Harvard Wyss
>      Institute for Biologically Inspired Engineering, observed that
>      evolution favors shorter lifespans in environments where resources are
>      scarce and when pressures to procreate are particularly intense. The
>      simulations appeared to show that lifespans of animals — humans
>      included — are genetically conditioned, and not the result of gradual
>      wear-and-tear. It’s a surprising result, one that gives added credence
>      to the burgeoning paradigm known as “programmed aging.”

>      ------------
> 
>      This new theory is still controversial and the article continues to
>      discuss the alternatives.
>      Aubrey de Grey also comments.
> 
>      But I like it. Resource driven ageing via evolution just seems 'right'.
> 
>    ### Sounds like complete nonsense. You can produce arbitrary results in
>    complex models by fiddling with your parameters, so this modeling effort
>    is not evidence of anything.

Impossible to tell without actual code. The main paper is paywalled,
and probably doesn't have code anyway.

>    There are a few known examples of predetermined lifespans (e.g. mayflies,
>    bamboo) but these are not related to aging, and are not applicable to
>    humans. Humans only infrequently age under natural conditions, the vast
>    majority die long before aging sets in, so any evolved mechanism actively
>    killing old humans as an adaptation would very quickly be removed by
>    random genetic drift (just like skin pigment disappears in cave-dwelling
>    animals - it's not an active adaptation but rather lack of selective
>    pressure needed to maintain the genes for pigmentation).

Whoa! What definition of aging are you using? In the serious human
models I've seen, humans age markedly, and this fact is reflected in
the human life table. John Graunt's table is the oldest I've
seen. Some birds, notably seabirds, were long thought not to age
because they had an apparently constant rate of death, but recent
careful work shows that they do eventually start to age.

Graunt's table is below.

"76, we, having seven Decads between six and 76, we sought six
mean proportional numbers between 64, the remainer, living at six
years, and the one, which survives 76, and finde, that the numbers
following are practically near enough to the truth; for men do not
die in exact Proportions, nor in Fractions: from when arises this
Table following.
 Viz. of 100 there
                              The fourth            6
dies
within the first six
                      36      The next              4
years
The next ten years,
                              The next              3
or
Decad                 24      The next              2

The second Decad       15       The next               1
The third Decad        09
  10. From whence it follows, that of the said 100 conceived there
remains alive at six years end 64.
  At Sixteen years
                       40       At Fifty six           6
end
At Twenty six          25       At Sixty six           3
At Tirty six           16       At Seventy six         1
At Fourty six          10       At Eight               0
  11. It follows also, that of all, which have been conceived, there
are now alive 40 per Cent. above sixteen years old, 25 above twenty
six years old, & sic deinceps, as in the above Table: there are
therefore of Aged between 16, and 56, the number of 40, less by six,
viz. 34; of between 26, and 66, the number of 25 less by three, viz.
22: sic deniceps.
Wherefore, supposing there be 199112 Males, and the number
between 16, and 56, being 34. It follows, there are 34 per Cent. of
all those Males fighting Men in London, that is 67694, viz. near
70000: the truth whereof I leave to examination, only the 1/5. of
67694, viz. 13539. is to be added for Westminster, Step{62}
ney, Lambeth, and the other distant Parishes, making in all 81233
fighting Men.
  12. The next enquiry shall be, In how long time the City of
London shall, by the ordinary proportion of Breeding, and Dying,
double its breeding People. I answer in about seven years, and
(Plagues considered) eight. Wherefore since there be 24000 pair of
Breeders, that is 1/8. of the whole, it follows, that in eight times
eight years the whole People of the City shall double without the
access of Foreigners: the which contradicts not our Accompt of its
growing from two to five in 56 years with such accesses.
  13. According to the this proportion, one couple viz. Adam and
Eve, doubling themselves every 64 years of the 5610 years, which is
the age of the World according to the Scriptures, shall produce far
more People, than are now in it. Wherefore the World is not above
100 thousand years, old as some vainly Imagine, nor above what the
Scripture makes it.

-rex
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