From: Keith Henson (firstname.lastname@example.org)
Date: Thu Aug 26 2004 - 21:02:04 MDT
At 03:02 AM 17/08/04 -0400, you wrote:
>Keith Henson wrote:
>>PS. Wars are *adaptive* for hunter gatherer societies. That does not
>>make necessarily make wars adaptive to later societies.
>I am not sure this follows from the fact that hunter-gatherer societies
>war. It could be the equivalent of a mutual defection in the Prisoner's
>Dilemma; not adaptive when compared to mutual cooperation, but still a
That's certainly a point to consider. But in an environment with no birth
control, and a fixed technology base where chipped rocks are high tech, I
don't see what form mutual cooperation might take. Any thoughts?
>I do not find convincing, as words on paper, the argument that the losing
>tribe's women and children would be absorbed and that this is preferable
>to mutual starvation.
Darn near anything that does not kill everybody concerned is better than
>I want to see a mathematical model describing the necessary conditions for
>this, or a study of reproductive outcomes in hunter-gatherer tribes.
Serious fluctuations in the carrying capacity of the ecosystem happening
once ever few years to once every few generations would be enough and
certainly within the range we have seen in the tree ring and other records.
>There is no obvious genetic reason for a tribe to adopt male children,
Generally they were not, though there were exceptions where an awful lot of
the tribe's males had been killed off.
>and as I recall my childhood Torah studies, "God" told the Israelites to
>kill off all conquered tribesfolk except virgin girls. That's not many
Better than none.
Taking a typical episode, consider a fluctuation where two equal sized
tribes occupy an area where there is a food reduction where only 75% of
them would live through it.
Assume that tribal behavior is the outcome of genes A and S for attack vs
starve, and the tribe takes the course of the majority. Further, let's
assume that before this episode, the genes are close to a 50/50
distribution. (S type tribe 45/55 split, A type 55/45 split, first
attacker type 60/40 A/S ratio.) It is also reasonable to assume that being
attacked is enough to get even a tribe with a slight majority of S genes to
There are three conditions, both S, both A, and one S the other A. There
is the well known factor that surprise attacks are more effective, the
tribe with the higher A percentage attacks first and gets some advantage,
but the outcome is not highly biased, say 60/40 for win/lose if you attack
first. Assume the young women carry the A and S genes in the same ratio as
the males and that the next generation of the mixed tribe carries S and A
genes in the same proportions.
Both S, both tribes take a 25% hit in numbers, equal male and female
deaths. The tribes will be slower to rebound when the ecosystem becomes
Both A, the tribe with the higher numbers of A attacks first and has a 60
percent chance of winning. For simplicity the winning tribe kills the
losing males without loss. Since the food and population ratio has been
restored, all the females and enough males get through the hard times. The
numbers work that the next generation has about the same A to S ratio.
.6 x (.60 (1) + .55(.5) /1.5 = .35
.4 x (.60 (.5) + .55(1)/1.5 = .27
So given these numbers the A genes have crept up to .62, not much but in
the right direction.
One S and one A.
in the case the S tribe wins (40%),
.45(1) + .55(.5)/1.5 = .4833 (.1933)
if they lose (60%)
.45(.5) + .55(1)/1.5 = .5166 (.31)
So on average the resultant would still be a tribe slightly over attack
So as long as there are collections of tribes with A genes slightly in the
lead, the next generation will be more prone to war.
The factor that might make this go quicker is the sized of the next
generation. Tribes that had collectively killed half the males to get
through the hard times would bounce back faster with twice as many women.
Now that I have been thinking about this, it is known that other hominids,
up to and including Neanderthals died out in contact with our kind of
human. Wars of this kind are, I make the case, based on anticipation of
bleak prospects. It could be that the ability to anticipate future
hardships (because the game had mostly been killed or the berry crop
failed) was unique to our line and induced us to kill not only fellow
members of our species when hard times were a-coming, but other species in
the same ecological niche.
PS. The check to prevent this from running away is that being too prone to
fighting when not justified by a worse alternative is not conducive to
getting your genes into the next generation.
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