Re: What is a hag?

In article <49f98967.11715125@xxxxxxxxxxxxxxxxxx>,
spam@xxxxxxxxxxxxxxxxxxxx (Jonathan L Cunningham) wrote:

He also, of course, produced the explanation of the equal pattern in the
normal case. And it's approximately even numbers at birth, not at
adulthood. For the same reason that it's even numbers in the elephant
seal case. Explanation available if desired.

At birth? That's illogical. Why not at 6 months pregnancy, or 2 years
old, or 3 years? Birth seems a bit of an arbitrary point. What about
egg-laying species? What counts as birth? When the egg is laid, or when
it hatches? Or for turtle eggs laid on beaches, when it hatches, or when
the baby turtle makes it into the sea (while its brother and sisters are
being eaten by predators).

Yes, please. I'd be happy with a link to an explanation of why "at
birth".

http://www.daviddfriedman.com/Academic/Price_Theory/PThy_Chapter_1/PThy_C
HAP_1.html

Go down to the subhead "Economics and Evolution"

The basic result is that, in equilibrium, cost (to parents of producing
a child) is proportional to value (in parental reproductive
success--loosely speaking, number of grandchildren) for reasons very
closely analogous to the reasons for the corresponding relation in
economics--which is why the discussion is in an economics textbook.

Consider the simple case, true for many species, where the only cost is
the production of the infant. If the parents can equally easily produce
one male or one female, and the m/f ration was not 1, then the parents
could produce more grandchildren by producing one more of the less
common gender, one fewer of the more common. Parents with a tendency to
do so would have more descendants, so the tendency would spread through
the population, and continue doing so until the ratio got to 1.

Next consider the elephant seal case--the male newborn is (say) twice as
heavy as the female, so requires about twice as much biological input
from the mother to produce. The choice is now between one male or two
female. Those alternatives give the same reproductive success if the m/f
ratio is one male to two females, since that means that one male has, on
average, as many offspring as two females.

Next consider the case where the cost of producing the newborn is the
same for male or female but, for some reason, half the males and none of
the females die before reaching reproductive age. The cost of producing
a male of reproductive age is now twice that of producing a female of
reproductive age, since you have to produce two males to get one to
adulthood, so you are back with the elephant seal case. But that now
means that you are producing twice as many adult females as adult males,
just as with newborn elephant seals, so the same number of newborns.

Things get more complicated if the parents make substantial investments
in the offspring after birth. If the dieoff happened in the first week
after birth and the parental investments were later and, for simplicity,
the biological investment to produce the newborn is assumed negligible
in comparison to the later investment, you then get to your result, for
reasons you can probably work out for yourself. But that's a very
special case.

--
http://www.daviddfriedman.com/ http://daviddfriedman.blogspot.com/
Author of
_Future Imperfect: Technology and Freedom in an Uncertain World_,
Cambridge University Press.
.

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