Re: Incest taboos

Bryant (
6 May 1995 20:41:58 -0600

In article <>,
Gil Hardwick <> wrote:
>In article <D7K0pp.M4L@murdoch.acc.Virginia.EDU>, Robert C. Craighurst
>> I apologize if this has already been discussed. I'm in computer
>>science studying a field called genetic algorithms. I've incorporated
>>the notion of incest into my computer programs.
>> How universal is the notion of prohibiting incest (by any
>>recognizable definition)? For example, do ALL human cultures prohibit
>>incest in some way? Are there ANY that don't care. If so, how rare are they
>>(roughly)? Any references in the literature?
>Tasmanians and Appalacian hill-billies are reputed not to care about
>rooting their own sisters, if that is of any use to you. Although I
>don't know that they have much of an interest in computers anyway,


Firstly, don't mind Gil. Although useless, his response was
pretty mild compared to his previous rants. Actually, I think I detected
some vague compliment in his post.

Secondly, your research sounds very interesting. Most cultures
do have some form of incest taboo, but what is considered "incest" is
variable. Sometimes, first cousins on one's mother's side are not to be
married (or had sex with), while paternal first cousins are not
considered close kin. That sort of thing. I do not know of any cultures
that allow sibling mating, save royalists in relatively recent European

You may be interested in reading work done regarding the
"Westermark Effect," however, which suggests that there is a biological
(psychological) mechanism for incest avoidance, quite apart from one's
cultural context.

Westermark found that children raised in close contact (as sibs
would have been in our evolutionary past) show aversion towards one another
as mates in the mid teens or later.
Of course, sex play amongst sibs is not apparently rare in
the late pre-teen childhood; these games don't translate into adult
sexual preferences, however.

I imagine that the Westermark Effect could productively be
investigated as an evolutionary adaptation for incest avoidance. Since
humans lack kin-recognition pheramones and the like (apparently), it
would make sense that we would pay attention to whom we are raised with,
and avoid them as mates. I'm not sure what the exact cues are. Watching
Macushi children (Brazil) interact, it was obvious to me that one boy had a
terrible crush on a girl that was the same age. They were raised exactly
one hut apart. No avoidance there, but they were ~10 years old.
It would be interesting if anthropologists out
there investigated threshold ages for this effect. Presumably, kids
thrown together as step-sibs in the mid-teens will not show this

Email me if you would like to get the Westermark refs. I am not
sure how relevant it will be to your GA work, but it may be informative
background material.