population, infanticide

Lisa Rogers eqwq.lrogers at state.ut.us
Mon Feb 26 18:26:50 MST 1996

From: rahul at hagar.ph.utexas.edu (Rahul Mahajan)
Date: Sun, 28 Jan 1996 16:49:02 -0600
Subject: Re: M.Harris, population, infanticide, warfare, male
As to your objections, I'm a little disappointed. You don't really
seem to have answered most of the points I made....  I hope we don't
start talking past each other ...

Well, Rahul, I spent some time composing a reply to this one a couple
weeks ago, but I began to suspect that we were already not quite
connecting.  But, perhaps together we could work it out, because I'd
like to continue this thread.

Thing is, I can't do very much more on evidence for/against
sex-biased infanticide in small-scale hunting/farming warring
peoples.  I already gave up what I had in a post previous to yours.
When I'm not so swamped I might look for some more recent literature,
but I expect that the lack of evidence _for_ it may continue to
appear as unconvincing evidence _against_ it, and that is the
situation we may be stuck with.

We can never prove positively that something does _not_ exist, eh?
Best we can do is design a good data-collection program, give it a
good shot and whatever we don't see, we don't see, which I think
Chagnon did, but I don't know if it's been repeated.  With no direct
evidence of sex-biased infanticide, a male/female sex ratio of 125 %
does indeed seem puzzling, I agree.  What we can make of it, I don't
know and we may not agree, but I'm sure we can live with that.

I am curious about a few of your other comments, if you'd like to
take one/any of them up.

R: Since we are talking about evolution by some combination of
natural selection and cultural evolution, any Darwinian objections to
group selection certainly don't apply.

L: Why not?

R:... of course pop growth slows down, the question is by what
mechanism. ... the population control must take place ... by some
human-determined method of resource allocation, whether it's
explicitly bashing in the brains of girl-babies or some more complex,
partly subconscious diversion of sufficient nutrition from girls,

L:  There are other potential mechanisms.  If you're interested, I'll
offer up a post on that.

R: ... I said Harris posited ever-present warfare as a mechanism for
pop control, which I said was a weakness in his argument. ...
As scientists, we constantly have to argue post hoc, ergo propter
hoc, no?

L: Well, I hope to do better than that.  Sometimes, I'd rather say I
just don't know, or there is insufficient data to make a clear call.

I hope you're not denying that superstructural components can have
independent force and effects.

L:  Well, perhaps I'm not sure just what you mean by that.  It's true
that I'm not a culturist, I have studied little about ideology, and
generally focus upon material/social forces.  I don't expect
superstructural things to be entirely independent of social/material
construction or effect.

R:  I thought there was copious evidence of female infanticide. I can
claim with complete confidence on the basis of extensive
documentation that it goes on at very high rates in parts of China
and India.

L:  We agree on that.  But I've never seen such evidence for
smaller-scale, non-stratified societies.  Nor the evidence of
sex-biased malnutrition, neglect and such among children, like I've
seen for, say, rural Pakistan.

R:  After all, random variation ought to cut both ways.

L:  Sure, I'm not suggesting that 'unusual' sex-ratios are random, or
due to sampling error.

You asked about the other hypothesis I mentioned.  Here goes, in
somewhat simplified form.

When thinking about the sex ratio among offspring from an
evolutionary/selective point of view, the question is 'what sex ratio
will give a parent the highest expected number of descendants?'
Let's pick grandchildren to count and compare, to see what the
results of various physiological/behavioral strategies may be.

Since every grand-offspring will have one mother and one father, then
on average all their mothers will have reproductive success equal to
that of their fathers.  Therefore, to get one's genes into
grand-offspring, one will do just as well to have daughters as to
have sons.

This is the basic logic that seems to account for the generally 50/50
[or 100%] sex ratios which are very common among many animals and
plants.  [I think this was worked out by Fisher, if I recall

One can imagine a test for evolutionary stability of this population
average.  If there were many more females born, then males would have
higher average reproduction than females.  Then those that bore more
males would have an advantage in number of grandchildren, and the sex
ratio would be brought back toward equality.  Same thing if many more
males were born than females, males would have lower average
reproduction than females, there would be an advantage to bearing
more females, and again the ratio returns toward equal.  This kind of
feedback mechanism prevents or counteracts drift.

This equilibrium can be changed by some things, such as if the sexes
are very different in the cost of raising them, or if they have very
different death rates before completing their lifetime reproduction.
Many factors may come down to affecting the expected reproduction of
females vs males, as well as more specific circumstances possibly
affecting the likely success of various individuals.

What it comes down to is that a parent is expected to put equal
amounts of reproductive resources into female offspring and male
offspring, when some ceteris paribum conditions are met.  Otherwise,
one can predict the direction of the deviation, if the response is to
be adaptive.

This assumes strategic reproduction, fundamentally warranted by
evolutionary theory.  The mechanism of the adjustment of sex ratio is
not specified, it could be a variety of things.  In some animal
studies, some control of offspring sex is exerted by sex-selective
spontaneous abortion, a physiological response that has adaptive
effects, and is activated in response to specific environmental
circumstances.  It may be that some human infanticide, where it is
observed, is consistent with this hypothesis.

Given the circumstance that there is a very high death rate for young
adult men, such that on average boys are 'cheaper' to raise than
girls, it would be consistent to expect more boys to be born.

There was some study of stratified female-infanticidal societies from
a reproductive strategy point of view a little different from this,
in terms of how expensive it would be for different classes of people
to get advantageous marriages arranged [bought, with dowries and
such] in China and the mid-East.  I think it was in the 80's and I
think the author was M. Borgerhoff-Mulder, in case you're interested.
 The effects of class/income on the reproductive/marriage prospects
of young adults in those societies looked very strong.

To remind anybody who might wonder, if it matters, this is related to
marxism in terms of trying to understand the social totality, the way
that material forces affect human/social behavior, and the mechanisms
of population growth or the lack thereof.

Rahul, if I'm not getting or addressing the points you had in mind,
please clarify.  I was previously addressing Marvin Harris more
directly, as that was the on-going thread before you joined it.



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