Re: Intelligence on the X chromosome

catherine yronwode (
Mon, 19 Aug 1996 15:42:08 -0800

Matt Beckwith wrote:

> The X chromosomes of a daughter come from both parents.

Yes, but the (hypotehtical) intelligence genes that are *expressed* may
come from one parent or the other or both (or so the current theory
goes). Remember -- multiple alleles, cross-over, dominance versus
recessiveness, all that stuff.

> The X chromosome
> of a son, however, comes from the mother (only). So a son's intelligence
> comes entirely from his mother.

Right (or so the current theory goes).

> In a patriarchal society, intelligence only has value as a trait in
> the males of the tribe (because they're the leaders). The function of
> the females is to pass that intelligence genetically on to male
> inheritors. But it has to go from the intelligent male through his
> daughter on to the intelligent grandson.
> So we don't want the leader's daughters leaving the tribe.


> It doesn't matter whether he marries within the tribe.

WRONG. If he marries outside the tribe, his children are not "of the
tribe." In traditional patriarchal matrilineal Judaism, for example, a
man who marries a "shikse" (non-Jewish woman) has children who are "not
legally Jewish" according to Jewish law. In other words, using this
model, he has produced children of UNKNOWN intelligence -- the
daughters' intelligence being irrellevant since they can't rule, and the
sons' intellligence being determined by their non-tribal mother, and
hence unknown by the tribe.

> It only matters that his daughters remain within the tribe (whether
> his wife is of the tribe or not).

WRONG. His wife MUST be of the tribe. His daughters may marry ANY man of
ANY tribe because their SONS (daughters don't count as rulers in this
model) will have the intellegence of their mom or dad (the ruler) or
both. In Jewish law, the children of a Jewish woman who martries a goy
(non-Jew) are fully Jewish.

> Now, what about the mating of his daughter? She now has the
> intelligent gene.

NOT NECESSARILY. She may have the intellegence of her mother.

> It doesn't matter whether she marries within or
> without the tribe.

RIGHT. She can be assumed to have the intelligence of her mother or
father (the ruler) or both -- but in any case she (and her sisters) are
the ruler's ONLY chance to pass his intelligence along.

> But her child--if male--must stay within the tribe. Otherwise the
> tribe is giving away a potentially ruling (and therefore competing)
> male.

RIGHT. No matter who her husband is, her son is the ruler's only hope to
pass along his intelligence to a ruler.

> So it would seem to me that, in order to keep the intelligent ruling
> genes in the tribe, daughters of rulers should stay within the tribe,
> and grandsons of rulers should stay within the tribe. Sons of rulers
> could do anything they wanted, as could granddaughters of rulers.

RIGHT, more or less. Sons of rulers might be intelligent too (from their
mothers) so if they marry in the tribe to an intelligent woman, that's
okay. It's when they marry out that their kids must be discarded from
the lineage.

Daughters and granddaughters of rulers make good wives for sons of the
ruler's viziers and stewards, because this gives a chance for
consolidation of the ruler's intelligence in the vizier or steward line.
The daughters of such collaterally-bred viziers' and stewards' offspring
make good wives for the ruler's male grandsons. We don't call it
inbreeding then...

> In a patriarchal matrilineal society, daughters of rulers who marry
> out are lost.

Yes. Both sons and daughters of rulers who marry out are lost to the
tribe. See above (and below) for my statements on traditional
patriarchal matrilineal Jewish law.

> So this is not the optimal social structure for
> optimizing intelligence when the intelligence genes are on the X
> chromosome.

No -- you've jumped to the wrong conclusion because you've failed to
understand the social structure. Being Jewish myself, perhaps i failed
to make it clear on first posting because i assumed everyone knows the

> On the other hand, there probably would never be a society structured
> in this particular way.

Yes, Judaism is indeed structured thus, as i noted.

For instance:

My mother is Jewish, my father Sicilian Catholic. Legally i am "fully
Jewish" (by Jewish law, not civil law). My co-parent is Jewish on both
sides of his family ("fully Jewish" by Jewish law). Our daughter is
"fully Jewish" by law, even though she is 1/4 Sicilian by genetic rules.
In short, Judiasm does not recognize "half-Jewish" as a classification.
One is either the offspring of a Jewish mother -- in which case one is
"fully Jewish" or one is the offspring of a "non-Jewish" mother -- in
which case one is "non-Jewish."

As an example of this working in the other way, take my step-sister's
case versus the case of my half-sister:

My step-sister's mother is German Protestant on both sides of the family
("non-Jewish"). Her father is born of the marriage of male Jew and a
female Protestant. By genetics, her father is 1/2 Jewish, just like me,
but by Jewish law he is "NON-Jewish." My step-sister is 1/4 Jewish
genetically, but because her mother is "non-jewish" and her father is
"non-Jewish," she is "non-Jewish" by Jewish law. She married a Jew who
is Jewish on both sides of his family ("fully jewish" boith genetically
and by jewish law) and they had two sons. Her sons are "NON-Jewish" by
Jewish law, even though they are 5/8 Jewish genetically -- because she,
their mother, is "non-Jewish" because HER MOTHER was not Jewish.

My half-sister, on the other hand, IS Jewish by Jewish law. Her father
-- the same genetically 1/2 Jewish man who is "non-Jewish" by Jewish
law (see above) -- married my mother, who both "fully Jewish" by Jewish
law (all her maternal ancestors being Jewish) and genetically Jeiwsh on
both sides of her family at least as far back as the early 1700s. My
step sister is thus "fully Jewish" by Jewish law but only 3/4 Jewish by
genetic rules. She has married a man who is English Protestant on both
sides of his family ("non-Jewish" by Jewish law). Any children they have
will be "fully Jewish" by Jewish law although only 3/8 Jewish by genetic

Now consider our children:

My daughter is 3/4 Jewish genetically and "fully Jewish" legally and all
her children will be Jewish by Jewish law, no matter who the father is.

My step-sister's sons are 5/8 Jewish genetically and "NON-Jewish"
legally -- and only if they marry Jewish women will their children be
Jewish by Jewish law.

My half-sister's unborn children will be 3/8 Jewish genetically and
fully Jewish legally and no matter who they marry, their children will
be fully Jewish by Jewish law.

Why are my step-sister's sons (and my step-sister herself) considered
NON-Jewish even though they have more Jewish gene material than my
half-sister's unborn children will have? Because they have in their
ancestry a Jewish man who married a non-Jewish woman and his son, who
married a non-Jewish woman. Non-Jewish X-chromosome material got into
the mix. That's a no-no.

In other words, traditional Jewish law maximizes conservation of the
material on the X chromosome of the mother.

> The sons of an intelligent man are not getting his intelligence, so
> we'd like at least some of those to leave the tribe.

Well, that could be one way to do it, and if they marry non-tribe
females, we sure will do that, but alternatively, we'd want them to
marry women of the tribe of known high intelligence to consolidate
intelligence back into the ruler's lineage. Those vizier's daughters
look pretty good.

> If he married outside
> the tribe (in a matrilineal society) they would leave the tribe.

RIGHT. If he married an outsider, one whose intelligence was unknown to
us, we'd have no clue as to whether he'd increased or decreased the
intelligence of his children. Hence we'd be willing to discard these
"unknowns" from the tribe.

> In a matrilineal society, all sons of women within the tribe would be
> kept within the tribe, whether the women married out or not. These
> are the important sons to keep.

RIGHT. Preserve that X-chomosome stuff at all costs.

> Getting back to my hypothetical optimal social structure, it would
> seem to be best to have the leadership itself transmitted from father
> to daughter to grandson. A truly great male leader would want to have
> daughters (not sons).
> Isn't that ironic, considering how many men
> prefer sons to daughters.

RIGHT -- becasue having daughters is the ruler's ONLY chance (and not a
sure chance at that) of passing along his intelligence.

> A truly great female leader would want to
> have sons, not daughters.

NOT SO. She could have either.

All her sons would carry her intelligence and would have a chance (say
50%) of passing her intelligence to her granddaughters -- but she'd
worry a lot about who her sons married, because she'd know these sons
were a potential dead-end to her intelligence line (no matter who their
mates were) if they only had sons.

Daughters, on the other hand, might carry some, none, or all of her
intelligence -- but whatever they had, they would carry some of it to
the next generation, no matter who they married and there would never be
dead ends through a female line. So a mother should want a multiplicity
of daughters.

> We could extrapolate this to our present society. If you as an
> individual want your intelligence to live on, then you should prefer
> to have children opposite in gender to your own.

Not necessarily so. The inheritance of intelligence by females in this
hypotehical model is MIXED. Only in boys is it determined by the mother.
One should want a multiplicity of girls because even if some of them may
not pan out in terms of inheriting one's intellience, some will. All
boys are potential dead ends -- if they only have sons.

> If you're a man, only your daughters will get your intelligence genes.
> (Intelligent sons would get their intelligence entirely from their
> mother.) Your daughters' sons would get either your intelligence
> genes or those of your wife. So there's a fifty fifty chance
> (ignoring chromosomal crossovers) that your grandsons through your
> daughters will have your intelligence. (Your grandsons through your
> son won't have any of it.)


> Since your intelligence will only be
> transmitted purely into male descendents (they're the ones that get
> the single X chromosome, and aren't "polluted" by some X chromosome
> inherited from someone else), you should really be looking at male
> grandsons as your ultimate goal for preserving your own individual
> intelligence.

That's a short-term solution, because those grandsons might
be a dead-end if they only have sons. The ONLY way to proiduce a line of
intelligence with statistical (albeit not specific) confidence of
continuity is through female descendents. Your granddaughters are 50%
likely to carry it on, while your grandsons will carry it on in 50% of
their daughters and 0% of their sons.

> If you want to not only
> preserve your intelligence but enhance it, you should marry an
> intelligent woman.


> If you're not concerned about your great grandsons (perhaps you don't
> expect to live that long, for example), then you shouldn't care how
> dumb your daughter's husband is. (Isn't that interesting!)

And, substituting "Jewishness" for "intelligence," this is exactly what
Jewish law does -- it doesn't care how "Jewish" your daughter's hudsband
is. Also, i find it interesting to note how often "the daughter's dumb
husband" is a theme in situation comedy humour. Cf. "All in the Family."

> In any case, the
> intelligence of your daughter's husband will have no bearing on the
> intelligence of those male descendents who receive your particular
> intelligence genes.


> If you're a woman who wants to pass on her intelligence, then first of
> all you should realize that your particular mix of intelligence is
> probably not going to get passed on as is.

Correct. You are playing the odds, not going for specifics.

> Your descendents will none of
> them be you.

No -- here you overstate the case. You have to consider the role of
dominance and recessiveness in this multiple allele set-up. Some
daughters of a woman may indeed be complete "intelligence clones" of her
in terms of expression of genes, while some may be a mixed bag of
inheritance from her and her husband -- but none will be "entirely
other" as the son of a man will be. That's why a women should aim for a
multiplicity of daughters -- to give herself the best odds.

> You can't pass both of your X chromosomes down the tree to
> the same person without some inbreeding somewhere, and you wouldn't
> want that. But let's say you want your X chromosomes to show up in
> descendents maximally. They will maximally show up in males (since
> they're unpolluted by someone else's X chromosome). So you should
> also have as a goal an intelligent male descendent. But in your case,
> it may as well be a son, because each of your sons will get one or the
> other of your X chromosomes. So you want sons. And when you have
> sons, you can take all the credit for their intelligence (or lack of
> it).

Sure -- but sons are potentially DEAD ENDS. Unless you get into
inbreeding (a taboo) If a woman's sons have sons, those grandsons are
lost to posterity as far as the woman's X-chromosome material is
concerned. A multiplicity of daughters is a woman's best chance to pass
along her intelligence.

If you're a woman and want to preserve your intelligence you should
marry an intelligent man, and discard from consideration the male
offspring of your sons. You should also be prepared to discard even your
female grandchildren if your sons have married unintelligent women
("outside the tribe"). Meanwhile, you should have lots of daughters and
instruct your daughters to marry intellgent men and to tell their
children to do as you have done. In short, for a woman to enhance or
preserve intellignece, she should set up a matrilineal society.

> All of this assumes that all of the genes for intelligence are on the
> X chromosome, which of course hasn't been established.

Sure, this is all hypothesis.

> I'm intelligent. My mother was intelligent but not as intelligent as
> I am. My father was extremely intelligent. I always thought I got my
> intelligence from both parents, but mostly from my father. If this
> theory about the X chromosome having all of the intelligence genes is
> accurate, then my father's intelligence was irrelevant. I'm more
> intelligent than my mother because I only got one of her X
> chromosomes, and the one I got had the preponderance of the
> intelligent intelligence genes. Or there was an advantageous
> crossover at my mother.

Right -- and here we open up further hypotheses concerning dominant and
recessive genes, the expression of genes, etc. which, as you know, go
beyond the simple model so far under discussion.

> Let's say
> there were no crossovers anywhere. In that case, my intelligence could
> be my maternal grandfather's, or my maternal grandmother's father's,
> or my maternal grandmother's mother's father's, etc. In any case,
> barring crossovers, there was some male on up the maternal branches of
> my ancestral tree who was as intelligent as I. Believing as I do that
> intelligence is the most valuable and personality-determining feature
> of a human being, that male ancestor was in a sense I.

Again, this is all based on unspoken theories concerning the dominance
and recessiveness of the multiple-allele intelligence genes -- and while
your description of how this might work is accurate, we can only
theorize here...

> Hm, I wonder how often X chromosome crossovers occur. Naturally,
> they'd only occur in women, so their incidence would be half that of
> crossovers in any autosomal chromosome.

Right -- and if they occured with any great frequency, they'd throw a
corresponding percentage of what's been discussed above into a cocked

catherine yronwode -------------------------
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