inclusive fitness and the Yanamamo

Wed, 2 Feb 1994 17:39:00 PST

Wait a minute, Mike Lieber. I'm no fan of Chagnon's argument, but your
counterargument is flawed. You write:

"But the practice of female infanticide not only reduces the fitness of the
parents, but also resuces the fitness of the offspring of their offspring,
thereby reducing, not maximizing fitness, inclusive or otherwise. Now, the
way of getting around this contradiction is to posit a digital computer in
people's heads that is programmed with a cost-benefit analysis such that
before killing a girl baby, one or bth parents have already calculated the
short term costs vs. the long term benefits in terms of net offspring one or
two generations hence."

Certainly, as you have framed the situation, the conclusion is that female
infanticide must reduce fitness (inclusive or otherwise) etc. But you do
this by either positing that the agents act without any consideration of the
consequences and implications for fitness OR they must make a two or
three generation calcuation and clearly the latter is absurd. But
all the agents need calculate is: will my CURRENT offspring be more or less
likely to survive if I practise female infanticide? Fitness is not a measure
of number of offsrping, as you know, but numbers of surviving offspring in
the long run. Thus if I perceive that having another offspring will surely
lead to two of my current children dying, then the act of infanticide
increases fitness. That kind of calculation is not unreasonable. For
example, the shaman Samik (a Netsilik Eskimo) stated to Rasmussen:

"Once when there was
a famine Nagtok gave birth to a child, while people lay around about her
dying of hunger. What did that child want here? How could it live, when its
mother, who should give it life, was herself dried up and starving? So she
strangle it and allowed it to freeze and later on ate it."

And for the !Kung, Lorna Marshall writes:

"They spoke of the nourishment of
the children as teh primary reason [for infanticide]; they spoke in explicit
detail. They want children, all the children they can possibly have, but,
they explained, they cannot feed babies that are born too close together."

(p. 166 The !Kung of Nyae Nyae). I think it is evident that people can and
do calculate consequences additional children will have on the immediate

Thus infanticide can increase fitness, and the information
needed to operationalize that fitness is information that people have.

If you want to argue against sociobiology, perhaps a better example
would be the demographic transition in modern western populations where the
number of children decreases with economic well-being (and where the argument
has been that one has fewer children when the cost of a child goes up--but
the cost is that of, e.g., higher education, not the cost of subsistence.
Obviously, middle to upper income families in the U.S. can have more children
than they do without any consequence to the likelihood of the children

D. Read