Stanford University.
--push off into new terrain,
here-- yet another bucket.
But before doing that,
various bits of feedback
from office hours.
Hearing from TAs.
Getting a sense of where
the grand, gaping craters
of confusion are so far.
And apparently an
awful lot of them
were provided in the
last two days of lectures
with behavior genetics.
Various issues that came up.
Clearly, one of the most
complicated, inaccessible,
subtle, pain in
the neck concepts
in the whole class, which is
this heritability business.
So memorize the
following two sentences,
because it all comes down to
the difference between something
that is inherited and
how heritable a trait is.
The fact that humans
overwhelmingly
have five fingers reflects the
fact that the number of fingers
is an inherited trait.
The fact that, when there are
some circumstances of humans
having other than
five fingers, it
is overwhelmingly
due to environmental
something-or-others is
an indication of the fact
that, nonetheless, variability
around the number of fingers--
heritability is essentially 0%.
So get those two
sorted out, and you
have those two concepts
all under your belt
and very useful.
Why is it useful?
First off, why is
this one useful?
Because it is important
to know the distinction.
Everybody, for one
thing, out there
tends to view these as
telling the same thing.
And insofar as they think
it says the same thing,
they think that both terms
are referring to this.
Something that is genetically
regulated, genetically
determined-- whatever.
Two totally different terms.
So one reason to
obsess over this
is that when the
newspapers give us
our sound bite of
"scientists report that,"
it's usually this one
that they're reporting,
with one of those marvelously
misleading numbers.
Which then sets people up
for thinking they have just
been told how much
do genes "determine"
some average feature
of this trait.
So, important to
tell them apart.
The other reason of
getting this sorted out
is not to only unlearn
the nonsense aspects
and misinterpreting this term
but because understanding
that term gives you
a lot of insights
into when and how
you are getting
gene-environment interactions.
Caveat with that.
Saying "when and how
you're getting"--
you're always getting
gene-environment interactions.
Remember the quote
from the other day.
It's like saying,
which contributes
more to the volume of a square,
or the height, or the length,
or the roundiness, or whatever?
Yes, it's always
gene-environment interactions.
Saying, in what
ways are there some
of the more interesting ones,
dramatic ones, in what realms--
Understand this, and you
avoid this confusion.
Understand this,
and it gives you
insights into
gene-environment interactions.
OK.
Other issues that are coming up.
By now, we've looked at three
different broad approaches
to the biology of
social behavior.
The evolutionary stuff--
broadly stated-- the molecular,
the behavior genetics.
And what should
be clear by now is
if you were living inside
one of those buckets,
you hate each of the other
two and trash them entirely.
So we get to the first of our
great, conflicting points,
which is, does that mean
one of these is wrong?
No, one of them is not wrong.
None of them are wrong.
Some are more right
than others, and some
are a lot better than others.
But nonetheless,
these are all-- again,
from the very first
lecture-- different levels
of description.
Another way to begin to
think about this, in terms
of what we've now
been focusing on--
and this sort of coming up
from some questions afterward.
So by now we've had
the term "epigenetics."
That's come in in the
last couple of lectures.
And there are at least
three different levels,
three different buckets, with
which you can define the term.
What is epigenetics?
Epigenetics is the way
the culture, environment--
all of that-- affects biology.
That's a certain broad
way of stating that.
NodA stated that
way, you are making
biology synonymous with
genetics, which ain't so.
But nonetheless, that's
a certain broad level
of stating it.
In another discipline,
a very sort
of first pass at
molecular stuff,
what is epigenetics about?
It's the way in which
environments turns genes
on and off.
And at another level of
explanation, more reductive,
what is epigenetics about?
It is regulation of chromatin
remodeling and methylation
of genes and all of that.
Do not panic, if
that's not the level
you want to know it about.
That's the business
from the other day,
about changing access
of transcription factors
to DNA-- jargony
way of doing it.
Don't worry.
The main point being that this
is a completely different level
of defining this.
This is the whole point in here.
We are beginning to see
different disciplinary
approaches.
We are beginning to see where
one discipline has decided
they have answered a question.
This is how culture
affects biology?
Give me a break.
Show me which genes
we're talking about!
We're talking about genes, here.
Give me a break.
Show me-- is this chromatin
remodeling-- what's
the mechanism for it?
How reversible is it?
One discipline's answer is the
next one's starting point--
blah, blah.
One discipline's wonderfully
satisfying scientific answer
is the basis for
the next discipline
to be totally
contemptuous of them.
You call that science?
This is sort of the
whole point, here,
beginning to see how we could
chip out a way between these.
More bits of clarification.
Amid that, one of the things
that really came through
is-- in the sort of
ratio of praising
to trashing-- I was clearly
spending a lot of the last two
days trashing the
behavior-genetics approaches.
So a little bit of
clarification, there.
First off, we can
broadly divide what
came the last two days into
classical behavior genetics.
And that's the comparing
monozygotic and dizygotic
twins.
That's the adoption
studies, that's
the twins adopted at birth--
that's all of those approaches,
there.
Those are all the ones where
you were just inferring really
indirectly that there's
something genetically going
on there.
The other half, and much more
sort of the modern behavior
genetics, is marrying these
traditional approaches
with molecular biology.
And that was the business at
the end-- you know the gene,
and you kind of have an
idea of what it might do.
How does that map onto
behavioral variability
in humans?
You know the
behavior, and you've
got some sense of
its variability.
How does that map onto
variability in genes?
This is the much more powerful,
contemporary end of it.
So what is this end good for?
All it's good for is pronouncing
that something's genetic,
or it's 73% genetic
and then you trash it
because that's jibberish.
What it's good for mainly is--
OK, so you've got
an adoption study--
classical
behavior-genetic study--
where they're adopted right
at birth, within seconds,
and raised in
different households.
Oh, you haven't ruled
out environment!
Don't forget
prenatal environment.
Oh, you haven't ruled
out environment!
Remember the
nonrandom assignment
of adoption-- all of that.
Does this mean this
approach is useless?
No.
What it's good for is
demonstrating nonetheless well
we've just ruled out all
sorts of realms of environment
that people would
guess is consequential.
It's less consequential
than you think.
We haven't ruled out
environment entirely.
And just because it's all
gene-environment interaction,
we certainly can't come up
with a stupid number like that.
But what this is good
for is at least showing,
here's domains where
people-- a lot of people--
would have assumed there is
big environmental effects.
Much less than you would think.
So that's the much
more conservative, sort
of sobrietous thing that
people can do with that field.
The fact that far too
few of them actually
do that is reasons to trash--
no, well, nonetheless, there's
lots of good things
in behavior genetics.
But that's the limited
domain where it's useful.
OK, so just beginning
to get a sense, here,
of the various things
that are confusing.
Obviously, no one on
earth in any exam in here
is going to be asked to
choose which field is better
and which field gives
more-- you know, kum by ya
and all of that.
But just recognizing
the different approaches
and the wonderful
rainbow diversity of ways
to think about mating in
fruit flies or whatever.
And just beginning
to see by now,
this is what the
whole class is about.
Speaking of that, I recall
from the first class on that.
There's somebody in here who
I think was an English Lit
grad student.
If you have a chance, email me
about how it's going in here.
Let's see.
What else?
Next week.
[LAUGHTER]
No, I'm curious.
I am very pleased
whoever you are--
assuming you haven't fled after
the first class-- is in here.
Let's see.
Other stuff.
OK.
Schedule.
Next Monday, this
coming Monday, we
will have a lecture on yet
another of our disciplines,
ethology.
And we will see that's
a totally different way
of doing it-- blah, blah.
Wednesday, Friday,
and the following
Monday are the catch-up lectures
in class, taught by the TAs.
Two of the lectures,
introduction
to the nervous system.
The third one, introduction
to endocrinology.
It will be a broad overview.
It is explicitly designed
for people who have
no prior background in this.
But what I think is
probably a good idea is,
even if you believe you
have prior background in it,
maybe assume it might be a good
thing to get a refresher on it.
And this will be very useful.
Following that, we will
have two more lectures--
more advanced topics
and basic features
of neuroendocrinology-- and then
staggering into the midterm.
And then-- oh, then--
the second half comes.
Just a sense of what's coming.
OK.
So that's where we're at.
So now we transition
to the next subject,
here, which is-- no,
actually, before I forget--
how many-- did people see this--
the article in the New York
Times this morning about the
study-- the Chutes and Ladders
study?
Did anybody see it?
It was posted this--
nobody saw it?
This was-- you know the
game Chutes and Ladders?
OK, we all played
Chutes and Ladders.
This was this massive study
funded by the World Health
Organization where
what they did--
this is going to be
the definitive study
on the subject.
They showed that
people from Nepal
are better at playing
Chutes and Ladders than are
people from Belgium.
[LAUGHTER]
Cool study!
I don't know how
you guys missed it.
OK.
You need to know about this.
This is important.
What do you want to
know about this study?
This massive study shows
that people from Nepal
are better at Chutes and Ladders
than people from Belgium.
Ask me questions, since
you were terribly, woefully
underinformed about this.
What more information
do you need
to be impressed and
tell everybody about it
in the dorm tonight?
What else you want to
know about this study?
[INTERPOSING VOICES]
"What does 'better' mean?"
OK, social relativist.
And does it mean that you
learn more about yourself
playing Chutes and Ladders?
[LAUGHTER]
Does it mean that you make
the world a happy-- you win!
You win, win, win!
OK, so winning is the end point.
Good question.
What else do you want
to know about the study?
Yeah.
Why?
Why?
Why?
You ask that?
Read Aristotle!
Since humans first
pulled out of the mud,
this has been the thing
we have wanted to know.
[LAUGHTER]
And now we do.
[LAUGHTER]
Son, the difference between
knowledge and wisdom--
OK, so, why?
OK, what else do
you want to know?
What are your questions?
Yeah.
What the methods
of the study were.
The methods.
Very good.
OK, various methods.
Do you want to break it
down into more details?
Given some of the
critical tools you
have by now, in
terms of methods,
before deciding how impressed
you are or not with this study.
What sort of questions, now,
in the methodological realm.
Yeah.
What population
they're sampling?
Ah, very good question.
Because we see a first
methodological issue.
Are you getting a
decent sample size,
so that you're confident that
you can actually say something
about the population at large.
And that's a great question.
It was done on everybody in
Nepal and everybody in Belgium.
[LAUGHTER]
Good study!
OK, what else do
you want to know?
What other questions?
Yeah.
In terms of their method, did
they pit people from Nepal
against people from
Belgium in one game, or--
Well, that's an
excellent question.
Every single person in the study
from both Belgium and Nepal
played one game against
every single other person
in the study.
[LAUGHTER]
That's why you
haven't been hearing
much about either country
in the news lately.
They've been very
busy with this study.
OK, so, good methodology,
large sample size,
random assignments of games.
What else you want to know?
Yeah.
Why-- the question and subject
to ask worth reading about,
and why did they [INAUDIBLE]?
Why'd they-- OK, that one again.
It's self-evident.
Know thyself, or know the
Nepalese and the Belgians
or something.
This is a-- I'm glad
I know this now.
I'm glad they went and did that.
OK, what else do
you want to know?
Obviously, a matter
of subjective
taste as to what counts as an
important scientific subject.
this strikes me as critical.
What else do you want
to know, in terms
of what sort of conclusions?
They kind of hint--
they're not positive--
but they're kind of hinting
at a genetic component to it.
Yeah-- question in
the back, there.
Yeah.
What skills are involved
in Chutes and Ladders?
What skills are involved?
It involves, um-- what is it?
They have a whole list, there.
Um-- let's see.
Various tasks involving
spatial memory.
Various tasks involving reversal
performance and telekinesis.
[LAUGHTER]
So it taps into all
of those domains.
What else do you want
to know about the study?
Yeah
Is it inheritable?
Is it heritable?
Great-- oh, ho, ho,
is it heritable!
So which are you asking about?
OK, well, they did it.
They are suggesting there's
some degree of heritability.
And they did it right.
They went after all the issues
we've learned about by now.
Specifically, what I'm saying
is that every single person
in Nepal and in Belgium was
cross-fostered to somebody
in Ecuador.
[LAUGHTER]
In fact, they did it fetally,
right after conception.
[LAUGHTER]
So they can-- the
prenatal stuff.
What else do you want to
know, in order to decide,
am I impressed about the
fact that people from Nepal
are better at Chutes and Ladders
than people from Belgium?
Yeah.
Were they all good at
the exact same amount
of Chutes and
Ladders as children?
Oh!
Yes.
In fact, none of them had
been exposed to it before.
They were all raised
in hydroponic gardens,
without Chutes and Ladders--
[LAUGHTER]
--and they were only released
in time for doing this.
OK what else?
Yes.
What's the amount of variance
within each individual group?
Oh, good question!
Here we are, getting
to that-- all of that.
Everybody got the exact
same score from Nepal,
and everybody from Belgium
got the exact same score.
So that's kind of impressive.
Are you impressed yet?
Are you impressed enough
yet to go run out of here,
screaming with this news?
What else do you need to know?
Yeah.
Who went first?
Who went first?
They randomized it.
They randomized it by-- the
entire populations played, um--
oh, what is that--
Roshambo.
Roshambo, yes.
They played roshambo.
And, best of all, they had to
play roshambo in Esperanto.
Yes-- more.
What was the environment in
which they test [INAUDIBLE]?
OK, they were released
from the hydroponic garden,
and then all of them were placed
in a completely sterile bubble
environment, where
all they had in there
were copies of People magazine
in a language they didn't
understand.
So it was well--
[LAUGHTER]
Environment was very
well controlled-for.
What else do you need to know?
How much better were they?
Like, 0.001--
Ah!
Ah!
There we have it.
They had a huge sample size.
They cross-fostered as fetuses.
They controlled for environment.
They got everybody in there.
They did the right techniques.
They randomized at
every possible choice.
That is so impressive.
That is so impress--
How big is the difference?
Is it a big difference?
And this is a critical
thing to start putting there
in your armamentarium
of critical questions,
to start having skeptical ones.
Great.
You've got a whole
bunch of tools by now.
Whoa!
They said "genetic."
Did you control for this?
Did you control for that?
Whoa, they see a
difference, there.
Well, wait a second.
Did they all have the
same exper-- whoa,
did they have a big sample size?
All of it covered.
Great, wonderful,
perfect science.
They get every single
bit of it covered, there.
But then the critical
thing you better ask
is, how big is the difference?
Is it impressive or not?
Because we all think we've got
the basic tools-- or hopefully
we all have the basic tools--
for going at these issues.
OK, was a study
done in a way that
was clear-cut and unobjective?
Were people blinded
to whether or not
this person was
Nepalese or Belgian
or-- was there
appropriate blinding?
Was it done in a way that you
can falsify your finding--
in a sense, the definition
of experimental science?
Was it designed in--
was it independently
replicated by anybody else?
We all have those tools
under our belt by now.
But far too often, we are
not trained, at that point,
to say, wait a second.
Before I get all excited, how
big of a difference was it?
Let me give you a
real example of this.
And this was a paper,
about three years ago,
in the journal Science-- which
you should get a sense by now
that the journals
Science and Nature are
the two official biggie
ones on this planet,
in terms of credibility.
And this was a paper
having to do with IQ.
And this was a paper having
to do with IQ and birth order.
And what they showed
in this paper,
with spectacular statistical
confidence and as much
of, like, all the
controls in place
as you can ask for from the
hydroponically gardened fetuses
in Nepal-- they did
absolutely perfectly.
What they showed in
the definitive study,
with 250,000
18-year-olds in Norway,
was that there is a
reliable IQ difference
depending on whether you were
firstborn or latter-born.
OK, how many of
you are firstborn?
Whoa!
How many of you are only childs?
OK, how many of
you are number 2?
How many of you are
more than number 2?
OK, so, how many of
you think the highest
IQ comes from the firstborn?
[LAUGHTER]
OK, and we'll assume the
converse with the other group.
Did anybody just vote against
their own birth order?
[LAUGHTER]
Whoa-- OK.
Well, that's-- impressive.
We salute you.
OK, so they found a difference.
They found a
difference, which is,
firstborns-- in this very
statistically reliable way--
have higher IQ
than latter-borns.
They restricted the analysis
just to second-borns
to keep things clearer.
And they showed firstborns have
higher IQ than second-borns.
250,000 people--
as close as you can
get to all the people
from Nepal and Belgian.
Huge sample size.
So they report this.
This was the most
thorough study ever done.
So what sort of questions
do you want to ask?
Give me hypotheses
for what's going on.
Obviously, sort of
one is that, like,
the parents pour protein
into the ears of firstborn
and the second one just
gets Fritos or something.
But give me other hypotheses
for what could be happening.
Possible explanation
for this, in terms
of biological, sociocultural,
endo, immuno, psycho-- yeah.
I think we already know that
firstborns tend to be more,
like-- well, I mean-- it's
like the parents-- they're more
worried about making mistakes,
and they kind of raise them
harder, so to speak, and
then they sort of relax
on the second-born
child. [INAUDIBLE]
firstborns tend to go to college
more and stuff like that--
do more traditional [INAUDIBLE].
OK, so, great hypothesis.
It's more parental
investment in the firstborn,
and those are the ones
with the parents freak out
with everything.
And by the time
there's a third one,
they're all foraging
on their own
when they're six months old.
[LAUGHTER]
OK, so, parental investment.
They went after
that one correctly.
Here's what they showed,
to rule that out.
Which was, if you
are an only child,
you have a lower
IQ-- on the average,
blah blah-- then firstborns
who have younger siblings.
So it's not parental investment.
It's something about being
the firstborn of multiples.
Yeah.
[INAUDIBLE] firstborns
are expected
to kind of like [INAUDIBLE].
OK, so pressure on the
firstborns to be first born.
How would that raise IQ?
Um-- all right, just
kind of like-- kind
of like responsibility
[INAUDIBLE]?
OK, so that's one of
the models out there.
A variant on that
is, firstborns get
pushed into a tutoring
position, early on.
And the well-known fact
that occasionally now
within teaching
something actually
causes you to know what
you're talking about.
So the firstborns, because
of this tutoring role-- oh,
that would control
for the single child
versus the firstborn
difference, there.
So maybe it's a
tutoring phenomenon.
What else could be happening?
What other possible notions?
Yeah.
It depends what age you're
looking at the kids at.
Because if you're looking
at, like, actual children
and comparing IQs,
older children
will probably have higher IQs
because they've had longer time
in life to learn.
OK.
Great idea.
Up to age 12,
latter-borns tend to have
higher IQ than firstborns.
By age 18, which is when
this study was carried out,
it flips the other way around.
So, any hypotheses for why
this difference occurs?
Why, by 12 years of
age, latter-borns
tend to have higher
IQs than firstborns?
Why does that then
flip afterward?
Yeah.
[INAUDIBLE]
OK, so is it IQ testing--
some biases with that.
What would rule
against that, though,
is that the age
controlling for only
childs-- only children--
versus firstborns.
So that would definitely
be a possibility.
That was ruled out.
Yeah.
I think that I [INAUDIBLE]
in another class
that you said it had to do
with the ratio of adults
in the environment when
the kids were growing up.
So when there's
only one child, you
have more adults with higher
language skills, and--
Good.
OK, so another version of a
parental-investment model,
there, which is, the fewer
the children, the more
parental energy.
So, again, that's one of the
standard things in the field.
They ruled that out with
comparing the only children
versus firstborn child.
So that's been a dominant
model in the field,
so they had good
data against that.
Yeah.
Could it be the
age of the mother
when the baby is a fetus?
Oh, OK!
What's your idea about that?
Well, younger mothers--
maybe the fetal environment
is better, and
obviously older children
have younger mothers than their
siblings whose-- the mother
[INAUDIBLE]?
OK, so we've got an
intrauterine effect.
So we've got egg quality and
age of mom and all of that.
They controlled for that--
the age of the mother.
Can anybody think of something--
another intrauterine mechanism,
though-- for what's the
difference between being
the first fetus
who hits the womb
of your mother versus being
the second or third or fourth?
What's one of the biological
things that might happen?
Yeah.
Stress levels.
[INTERPOSING VOICES]
OK, stress levels, which is
a way of stating something
about intrauterine environment.
The more times you've
done this, perhaps more
stressed you are in there.
What else could biologically--
that's definitely
one of the things.
What else biologically
can happen, over time?
Remember progesterone,
the other day,
from that lecture of
making new if-then clauses
and glucocorticoids.
And this is a bit of a stretch.
This takes some sort of fair
amount of OB/GYN knowledge.
What's a danger as you have
more and more pregnancies,
in terms of your immune system?
[INAUDIBLE]
Yeah-- wait-- I
heard that mumbled!
Sure!
It gets surpressed?
Yeah.
OK, immune suppression.
So mom could be getting
a lot less healthy,
which is another version of
tapping into that notion,
there, in terms of
egg quality with age.
Separate of age, the number of
times you've gone through this.
What could be another
possibility, immunologically,
with repeated pregnancies?
Yeah?
A mother [INAUDIBLE] more,
like, form antigens [INAUDIBLE]?
OK, despite that immune
suppression, on the average,
with later pregnancies you
have a greater likelihood
of having formed antibodies
against aspects of the fetus.
They controlled for that.
They showed, if you
were second-born
and there were kids after
that-- if you were second-born
and the firstborn died, you
reverted to the firstborn IQ.
Showing that it was
not anything about,
oh, you were the second fetus
in there, with more antibodies.
They controlled for that.
That's actually one of the
ideas they brought up in there.
What else?
How about that business
about up to age 12,
the second-born does better?
After that, by age 18,
the firstborn does better.
Any theories with that?
Yeah.
Did it have to do, maybe,
with how fast they grow,
or something?
I know we talked about
how for fathers it's,
like, a child grows
faster [INAUDIBLE]
more later [INAUDIBLE]
grow faster then
that takes a toll on
your [INAUDIBLE] health?
OK, so an early advantage,
and you pay for it later,
type deal.
So that's a possibility.
What else could come in?
Think about-- back
to the idea, there,
about if you're a firstborn.
Some of the firstborn
responsibility stuff.
How that plays out in
family dynamics early on.
Why are the second-borns
doing better
in the first dozen years?
Why is it reversed later on?
More ideas about that.
Yeah.
The second-born benefits
from the tutelage
of the firstborn early in life.
But later on, having the
older having had that
experience of being more
responsible [INAUDIBLE].
Exactly.
That's one of the main theories.
That's probably the
predominant one proposed
to explain that age switch.
You get the second kid
show up, and suddenly you
have a neotenized,
dumbed-down environment,
where suddenly
the 8-year-old kid
is watching Tinky Winky again
for the first time in six
years.
That it's an environment
that's then dominated more
by having a younger one around.
And what the older one is
mostly doing is the tutoring.
And it takes a number of years
for the advantages of that
to finally come through.
That's the main model
that's given for that.
Any other ideas?
How about
parental-resource stuff?
The fact that the larger
the family, on the average,
in westernized countries, the
lower the socioeconomic status?
Run with that one.
Where does that fit in?
What else?
What else could be
happening with that?
Yeah.
If the socioeconomic status
of the family is lower,
then wouldn't that suggest
that the children might
bear more burden, in some
respects, with more children
around, so that they had
to grow up more quickly
and be exposed to
the real world?
It's the later ones who are
out hunting squirrels and not
getting the violin lessons.
That's another version of the
parental-resource one, one
being because there's a
smaller ratio of parents
to the kids, the other being
because the more kids, the more
expensive for the
same parental income.
And you have got less
to spread to each child.
So they controlled for that,
looking at within family
rather than just between family.
They covered all of this.
This is going to be
the definitive study
for the rest of all of
time, showing what's
going on with IQ by birth
order in 18-year-olds in Norway
in 2007.
What was the magnitude of the
difference for this study?
2.3 IQ points.
And thus, coming
back to what could
have been the very first
question sitting there
when these guys were
ready to announce this
to the world and
sort of start selling
their "be like a firstborn
IQ" self-help books and all
of that.
Lost in there-- and this was
picked up all over the press
and, like, no doubt, endless
snotty comments by David
Letterman or--
And nobody-- 2.3 IQ points!
You sneeze while you're
taking an IQ test
and have to wipe your nose
for eight seconds afterward,
and that's going to cost you
2.3 IQ points, because you
get distracted for a second.
An amazing example of this
whole business of-- yes,
impeccable science that these
people did-- phenomenal!
I don't know who possibly
gave them the money
to do a study like this.
And at the end of the
day, totally cool,
irrefutable, statistically
totally reliable--
which is very different
from saying "important."
But what you get at
the end of the day
was this mammoth study
producing 2.3 difference.
And this is a great
demonstration.
The difference between
how solid the science
is, how confident you are
of the finding-- which
takes in all the variables of
sample size and objectivity--
how confident you
are of the finding,
and how big of a finding it is.
And those could be two
entire differences.
So, as a [INAUDIBLE] you
to all the stuff that's
going to come in the second
half of the course, one
of the next tools you
have to have in mind,
in addition to all the
ones that were apparent
here in the questions you
were asking-- another one
is to keep saying, well,
is this a big effect?
"Is this a reliable
effect?" is different
from "Is this a big effect?"
"Is this a consequential one?"
So, another tool
to have in hand.
So, with that in hand, go
and tell everybody tonight
about Chutes and Ladders.
OK.
So what we jump to
now is something
that's been running through
a whole bunch of the lectures
already.
OK, we've got all those
evolutionary models
of individual selection and
kin selection and in-group
and out-group.
And we've got something
about the molecular biology
of why it is that you
share 50% of your genes
with this relative and 25 and
12 and a half, and all of that.
And somewhere in there,
lurking through all of it,
is a question
which is what we'll
focus on now, which is, how
do organisms, how do animals,
how do individuals
recognize relatives?
Because you can't do any of
that evolutionary-biology,
kin-selection-theory stuff,
where it's all predicated
on degree of relatedness,
unless you know how related
am I with this individual.
So what we're going to be
looking at, here, is, why--
or how-- sure, let's go for
"how" instead of "why"--
how do animals, how do social
animals, recognize kin?
What's clear is, it does not
take a very fancy organism.
And there was a great
example of this,
which I think I stuck in the
extended notes, last minute--
a paper published just a couple
weeks ago looking at deer mice.
Deer mice, and much like
their vole cousins--
if they are cousins--
some deer-mice strains are
monogamous, and
some are polygamous.
This appears to be
a frequent theme
in these little rodent things.
And with the deer
mice, what you find
is, with the polygamous
ones one female mates
with a bunch of males.
And as a result,
one female will have
sperm from a number of different
males afterward in the vagina.
And what you get
is, evolutionarily,
from all the rules we learned
by now, perfectly logically,
you get intrasexual
competition between the sperm
from the different males.
We already heard
a version of that
with the flies,
back the other week,
there, where the
sperm of one releases
toxins that kill the other
sperm but in the process could
damage the female's
future-- all of that.
This is a theme that runs
through a lot of the literature
on sexual competition.
Sperm competition.
And there's even hints
that something like that
goes on in humans.
OK.
So what form does it take?
In these deer mice, as follows.
I don't begin to understand
the mechanics of this,
nor do I want to.
But apparently, with
deer-mice sperm,
if they all clump
together-- you know,
many hands on the
oars, or something.
If they all clump together,
you get this macro sperm thing
which swims upstream faster.
And the paper had
all sorts of diagrams
of this which I did not want
to look at in much detail.
But there's this--
So you've got-- with
the polygamous strains,
you've got this problem.
If your sperm want to do
things absolutely correctly,
they only want to form
one of these big-old,
you know, pleasure-boat
aggregate crew things,
with sperm from themselves--
with sperm from only
themselves.
And, following all
of our theorizing,
to a lesser extent with close
relatives and not at all with
sperm from some other guy.
And that's precisely what
they showed in this paper.
You take sperm from
monogamous strains,
and you put sperm from
different males together,
and they all happily form this
big cooperative clump of sperm,
there.
But you take them
from species that
have evolved under the
selective pressure of polygamy,
and the sperm there know
who they're related to
and will form these clumps only
with the ones from themselves.
You can immediately design all
sorts of lock-and-key stories
for how it's pulled off.
You could immediately come
up with some approximation
of what the molecular
mechanism would be.
But for a first pass,
what's striking here is, oh,
how do organisms
recognize relatives?
There are, out
there, single cells
that can do this under
exactly the evolutionary
circumstances-- models
that we've got already.
So, as we begin to look, now,
at how whole organisms do it,
even cells can do it.
And we're going to see lots of
different possible mechanisms.
In lots of species, what you
have is some equivalent of what
those single sperm
are doing, which is,
there is innate
recognition of relatives.
How do you show this?
We already know the classic
ways of doing this, which is
the crossed-fostering approach.
You take a litter, newborn
litter, of your rodents,
and you cross-foster
them to other females.
And if, later on,
they can behaviorally
differentiate between their
siblings and nonsiblings,
there's something
innate about it.
Oh!
Wait a second, wait a second.
What about prenatal environment?
Wasn't there something
about-- so now you
do the prenatal
cross-fostering--
the fetal-transplant
approach-- and you get
the exact same thing.
There is innate
recognition of relatedness
in all sorts of rodent species.
Another way of doing
it even cleaner.
You have two different litters
from the same mother and father
rodent.
And then they meet together.
So there was no shared
prenatal environment.
And you can show
recognition there.
You put the rat, later
on, into the cage where
there is the urine
of its sibling,
and there is the urine
of a perfect stranger,
and they will prefer
going to that one.
You could show that it's
even more subtle than that.
They will prefer to go to
the urine of a full sibling
versus a half sibling, a half
sibling versus a first cousin--
all the way on down.
They could take it out to
about third or fourth cousins.
Incredible discrimination,
there, that can go into it.
And it has to be that way, or
else all of the theorizing from
the other day-- you can't figure
out how to give up your life
for two cousins or eight
brothers or eight brothers or--
[FEEDBACK]
--two cousins, or
whatever the math
is, unless you know who's who.
And in some species where it's
done entirely instinctually,
that would be the way
you demonstrate it.
So what's the mechanism,
, there, in those cases?
The most-studied
ones are olfactory.
Olfactory signatures.
"Pheromones"-- we've already
heard that term in here.
We're going to hear
tons more about it.
But pheromonal communication.
What does that begin to require?
If you have pheromones,
odorants, coming out of, say,
the urine from
different individuals,
telling you your degree
of relatedness to them,
it requires two things.
It requires qualitative
differences in the urine,
reflecting the genetic makeup
of the individual who provided
that urine to the grad student.
And it requires some mechanism,
some olfactory brain-processing
mechanism, to be able to pick up
whatever those differences are.
And both have been shown.
OK.
The way you begin to
get the differentiation
at the end of how the
urine smells differently.
What you've got--
and referred to back
with the transposable
stuff is-- you remember,
in vertebrates you've got
some of your highest rates
of transposable events
in your immune system,
your genes devoted to immunity,
where you juggle them around.
And that's how, with
any luck, you come up
with an antibody that will
recognize this completely
novel pathogen. All of that.
There's an additional
stretch of genes
in that neighborhood where
what happens with that is,
it also undergoes huge amounts
of splicing and transposition
and juggling and all of that.
And what do you do then is,
you create a completely unique
protein.
You do it in enough
of a combinatorial way
that it would take
statistically 400 quadrillion
googleflex-whatevers to come
up with another organism
with the exact same
protein signature.
When you make a
protein from that,
you have made up one that no
other organism on earth has,
with a very high
statistical reliability.
This is a stretch
of genes called
the "major histocompatibility
complex"-- MHCs.
And what you see with those
is histocompatibility,
that whole business with
organ transplants-- how
compatible of a donor is
it, how closely related,
how much of this--
jargon, for those of you
who know it-- how much of a
shared antigenic determinant,
how genetically similar is this
fingerprint, this identifying
ID of a protein?
That determines things
like histocompatibility--
how well organ transfers work.
That's the origins of the term.
So every single one of us,
every single organism out there,
has made an arguably unique
juggle of these genes
and comes up with
this signature protein
that it sticks on the surface of
every single one of its cells.
What's that good for?
That's good for
your immune system
learning, if we run into a
cell with one of those things,
it's us.
Don't attack it.
Don't form antibodies
against it.
And if we run into
anything else in here that
doesn't have one of those,
it's an invasive pathogen,
and go attack it.
This is the basis of the
self/nonself recognition
ability of the immune system.
And what autoimmune diseases
are is when your immune system
screws up and begins to mistake
one of your signature proteins,
your major
histocompatibility gene
derived signature protein,
as, in fact, being invasive.
And one of the other things
you hear about-- the other day,
we heard about this tropical
parasite, trypanosome.
What it does, as
you heard, was it
keeps juggling its
surface proteins.
So just as your immune system
is all set to attack it,
because it's got
antibodies to recognize it,
it has changed its
signature protein.
There's another tropical
parasite, schistosomes,
where what they do is they steal
your major histocompatibility
proteins from the surface
of some of your cells
and glue it on themselves.
And they are wolves in a
sheep major histocompatibility
proteins or some such things.
So that's one major domain where
this unique protein-- derived
from a unique gene--
unique protein signature
lets your immune
system work properly.
So it turns out there's another
whole domain with it, which
is, these proteins
can become soluble.
Which means they're no
longer anchored to a cell,
they're just floating around.
And ultimately they're
floating around in your saliva,
in your urine, in your armpit
exudates or whatever it is.
And what they begin to do--
complicated mechanisms, which
I think I will bypass.
What they do is give a unique
signature to the pheromones
coming off of you.
And, as we will
see in the lectures
to come, animals of all
sorts of species can tell,
is this individual
of my species,
are they the same gender,
are they an adult,
are they sexually
mature, are they healthy,
are they pregnant-- whatever.
But thanks to this
major-histocompatibility
business they can also
tell, is this a relative?
Now the juggling of events,
the splicing and the juggling
of the genes, has some degree
of statistical relatedness
the more closely
related you are.
In other words, you
smell your own urine--
if that's your hobby-- and the
major histocompatibility genes
in there will obviously
exactly match your own.
You smell those of
a full sibling--
even more questions to be
asked-- and you do that,
and there will be a greater
degree, statistically,
of similarity of the
structure of that protein
than with a second cousin,
than with a perfect stranger,
than with a Nepalese
if you're from Belgium.
Whatever it is, what you
find in those cases is,
that's how you not only
get innate olfactory
recognition of, is
this a relative or not,
but how related of a relative?
So that's half of it.
That's how you generate
the unique signature
at the olfaction at
the pheromone end.
The other trick is,
how do you generate
an olfactory system that can
make that discrimination?
And all we've got to go with, at
that point, is-- you can guess,
if you think about
it a bit-- is,
we've got to have some
version of olfactory receptors
that do the old
lock-and-key business.
Just as you make a protein
which has a certain shape,
indicating that this is
your unique signature.
What you want to do
is have receptors
that will have the uniquely
complimentary shape
for the lock and key so
that you can do a-- oh!
This fits perfectly.
Let's transduce this to a
signal to the brain, saying,
I'm smelling my armpit.
And if, instead, you've
got a protein that
fits in there like a lock and
key but not quite as well,
you send the message of, oh, I'm
smelling my sibling's armpit.
And if it fits in there not
quite as well, and all the way
down, you could begin to see
exactly how you designed this.
If you've got 1,000 of these
receptors of this shape
and every single one of them it
has them fitting in well enough
to stay in there for three
seconds, so that all 1,000
of them send the signal.
It takes three seconds
of binding there
to cause the signal to happen.
All 1,000 of them send the
signal that means "it's me."
It doesn't fit quite as well,
so, statistically, only 800
of them stay in there for three
seconds, so 800 of the cells
are reporting, oh,
that's a full sibling.
I don't know if
that's the mechanism.
But this would be a
way of constructing it.
That's exactly how it could
be, along the lines of lock
and key, genes produce
proteins of certain shapes,
certain functions-- all of that.
And that's how you
begin to do it.
What have we just gotten?
We've gotten a protein--
a molecular basis
of our theorizing, the other
day, of an if/then clause.
If and only if this
is a close relative,
then send a message to the
neurons that do "cooperation."
We already know
that's gibberish,
to say that there's neurons
that do cooperation.
But you could begin to see
how this is going to work.
This is the "if" part of
all the conditional if/then
clauses built around
degree of relatedness.
So how does your
olfactory bulb do this?
Very interestingly,
people are beginning
to get a sense of two hormones
that are relevant to this.
One is called
"oxytocin," and the other
is called "vasopressin."
And what we will see in lectures
to come is, particularly
in females, oxytocin
has long been
known to play some, like,
plumbing, nuts-and-bolts job
in giving birth, and vasopressin
in uterine contractions.
And take your average, like,
off-the-rack endocrinologist.
And what these
hormones are about
is, like, your uterus
contracting and giving birth.
But oh, that's so
little of what they do.
What they're much more
interestingly involved with
is what happens next.
Which is now
beginning to learn how
to recognize the smell
of the individual
you just gave birth to.
Because it turns out, what
oxytocin and vasopressin do
in the olfactory bulbs--
the olfactory system,
the olfactory equivalent
of your eyes and ears--
is they tune up the
cells that recognize
major histocompatibility
signals.
They make them attuned to,
is this a relative or not?
And there's an if/then clause.
If the levels of this hormone
have the certain high levels
indicating that I
just gave birth,
and I smell something whose
signature odorants fit really
well to this
receptor, then this is
someone who I'm going to nurse
like crazy, unless it turns out
to be my mother or grandmother.
OK, let's put it another-- if
they're very little and cutesy
and make cute little
mewling sounds,
then I will take care
of them and nurse them
and all that sort of thing.
And it's turning out that that's
what oxytocin and vasopressin
are doing in there.
You generate mice with
genetically-- knocking out
oxytocin or vasopressin
or their receptors--
if these are totally new terms,
this will come by the week
after next, as an introduction.
You knock out those
genes, and you get what
is called a "social anosmia."
Anosmia is the inability
to smell something.
A social anosmia is, your
nose is working just fine--
if you're a rat, you could
discriminate different food
types-- completely
arbitrary odors-- you just
can't distinguish
between individuals.
And there was a paper,
a couple of weeks ago,
showing for the first time--
what the model has always been
is that circulating
oxytocin and vasopressin
get into your olfactory
system and have those effects.
What this paper showed
for the first time is,
you're making those hormones
right in your nostrils,
to begin with.
This is what tunes it up.
Very interestingly,
there is also
a literature emerging
suggesting mutations
in genes relevant to
oxytocin and vasopressin
in families with a high
incidence of autism.
Autism, a disease where-- one
way of characterizing it is,
there are enormous deficits
in normal socialization
interaction, social
bonding, social affiliation.
And this suggests that has
something to do with it.
OK, so that's a first mechanism.
That's how it might
work innately.
Very cool study in recent years,
also showing one facet of this.
One of the things you get
taught in Intro Neuro--
if you've taken anytime
in the last 5,000 years--
is, when you've
got an adult brain,
it doesn't make
any more neurons.
You've got all the neurons
you're ever going to get,
by the time you're
three years old,
and all you can do thereafter
is squander them away on, like,
stupid weekend
binges or whatever.
And it turns out that,
nonetheless, this is not true.
And arguably this is the biggest
revolution in neuroscience
in the last decade or so.
Adult "neurogenesis."
And it turns out, this
adult neurogenesis
happens in only two
areas in the brain.
The first one is
really interesting.
Because it's this part of the
brain called the "hippocampus."
Hippocampus-- learning, memory.
It's totally cool.
And a gazillion studies
now showing stuff
like, you learn a new fact,
you stimulate neurogenesis
in your hippocampus.
You get put in an
enriched environment,
you exercise, you do
all sorts of stuff--
you make new neurons there.
You get stressed, you make
less new neurons there.
This whole new field.
And 99% of the studies have
been about these populations
of neural stem cells
in the hippocampus.
Totally ignored has been
the second, little pocket
of these neural stem cells
that can make new neurons.
Nobody's interested in it.
What's this about?
It's totally boring.
Where's the second pocket?
Just behind the olfactory bulb.
And what this study showed--
and this is one in your reader,
just at the abstract.
What it showed was, if
you have a rat right
around the time
she gets pregnant,
she starts to make a new
neurons out the wazoo--
not from the exciting
hippocampal pocket,
but from this boring,
little olfactory.
And what goes on with
the onset of pregnancy--
female rodents do this
massive renovation
job of all their olfactory
neurons going on, there.
What it is, they
showed in this study--
it is driven by the
prolactin levels that
rise during pregnancy.
And what have you got there?
What they showed was,
right around the time
she gives birth, she's got
this spanking-new, completely
renovated olfactory
system, just in time
to do one of the most important
olfactory things of her life,
which is quickly figure out
which ones are her babies.
To quickly do the
social bonding to them.
What hasn't been
tested yet, but what
I guarantee has to be there, is
that vasopressin and oxytocin
has to have some sort of
role going on in there.
Really interesting.
Interesting implication of this.
So think about this.
If you were pregnant-- and
assuming this works in mammals
other than rodents-- and
if you were pregnant--
so the whole time you were
pregnant, what's going on?
You're doing this huge
job of ripping out
the walls and the plumbing in
your olfactory bulb and, like,
putting in new stuff.
And it's a total mess.
Like, you spend your pregnancy
with your olfactory system
totally cockeyed.
No wonder stuff smells
weird, and no wonder foods
taste weird and all of that.
There is a whole
adaptationist literature
out there on, why should
it be that you suddenly
want pickles and these foods
you can't stand the taste of?
And it's to avoid
inadvertently eating toxins.
A really unconvincing,
spandrel-filled
literature out there.
It may be an inadvertent
spandrel byproduct of,
you're ripping apart the
whole olfactory system,
so you're all set to recognize
the smell of your kids.
You just got screwy
olfaction and taste
all throughout pregnancy.
The main point of
this, though, is,
this is endocrine
regulation driving,
not to make you
able to recognize
a relative-- because you've
already got the genes in place
for that-- just making sure
that your olfactory bulb is
at the very best at
that time for doing it.
OK.
What else does one want
to know about that?
OK, one additional thing you
could do with that information.
Which is, OK, so,
why do you want
to know who your relatives are?
It's who you mate with,
it's who you cooperate
with, it's who you
try to kill, it's
who you take care of, it's
who-- all that sort of thing.
All of these domains.
Also it's who you pay
attention to socially,
in terms of gossip and such.
One interesting
study that was shown,
which was with
baboons-- and this
was the same folks at the
University of Pennsylvania.
What they did was they
recorded the voices--
You notice this
business about playing
the voices of some
animal in the bushes
and looking at the
response in everybody else
is one of these standard tools.
What they did, in
this case, was,
the voice of two animals from
that group, from that troop.
And what we heard was the voice
of the lower-ranking animal
giving a dominating
vocalization,
and the voice of the
lower-ranking individual
giving this terrified
subordinating noise.
So they obviously were
not getting a terrified
subordinating noise
out of number 1,
but they had to sit
around and get recordings
of number 2 and everybody
else, at some point or other,
so now they could
put them down there.
And they would play this.
So everybody else is sitting
there and saying, what?
Number 4 is terrified
of number 27?
What's going on?
And what they showed was,
everybody paid a huge attention
to this, if they were hearing--
number 27 was trashing number
4 if they weren't relatives.
But if they were
in the same family,
and there was this dominance
reversal nobody paid attention.
Crazy relatives.
Who knows what's going
on in that family?
They're just squabbling.
They distinguish the
social implications
of a dominance
reversal, depending
on relatedness or not.
One additional thing
with it, before we
go to our next way of
recognizing relatives,
after the break-- hold on.
One additional
thing is, of course,
telling you who to mate with.
And it's obvious who you're
supposed to mate with,
in species after
species-- someone
who is not related to you.
Because if you do,
you may inadvertently
produce babies with two
tails and seven fingers
and all of that.
Nobody picked up on the
fact that actually we
have 10 fingers instead of
five, but we'll let that slide.
But what you get there
is, oh, avoid inbreeding.
Don't breed with relatives.
But we've already heard about
a counterargument, which
is, breed with relatives because
of the inclusive fitness,
the kin-selection
advantages of doing that.
And, from the
first minute people
started getting these
theoretical models,
it was clear that,
in fact, there
were contradictory
pulls between doing
major outbreeding in
your mating and doing
inbreeding with your mating.
And people did all
these theoretical models
of econometrics of where
you optimize the difference.
And they came out
with the conclusion
that, in all sorts of
species, the optimal balance
of avoiding inbreeding
disasters with advantages
of kin selection would
be to mate with something
like a third cousin.
And you go and look at all
sorts of species out there,
and that's precisely
what they do.
That's where it balances out.
And, again, you can't do that
unless you know relatedness.
Then, a couple of years ago,
along came this researcher--
Martha McClintock,
University of Chicago.
She's the person who discovered
the Wellesley effect back when.
And for all of you guys who are
gearing up for senior honors
theses, this was her senior
honors thesis-- discovering
the Wellesley effect.
So this was, like,
one impressive study.
Yeah?
Did Darwin marry a second
cousin? [INAUDIBLE]
Who did-- he married
a first cousin?
First cousin [INAUDIBLE].
First cousin.
There you go.
When we all know he would much
rather have married a Galapagos
tortoise, but his
parents forced him--
[LAUGHTER]
Well, interesting exam-- OK,
so you thus catapult us, here,
into the human realm.
What McClintock did was a
study, a couple of years
ago, where she took swabs-- she
has this whole paradigm of very
high-tech-- getting cotton
balls and rubbing it
on people's armpits and
putting it in a jar,
there, and then getting
these volunteers who
can [SNIFF] smell it and give
some assessment of how good it
smells or not.
Which, in and of
itself, is pretty wild.
And you run that with humans.
And of a curve of relatedness,
whose odor gets rated
as having the most appealing?
Third cousins.
Yuck!
Think about that one later.
We are just another
species, in that regard.
All of this suggesting,
even in humans,
you are balancing
this disadvantages
of inbreeding with the
kin-selection advantages.
And, again, there's no way you
can do that without knowing
who's related to what extent.
OK.
Five-minute break.
And what we'll then
transition to are,
species that don't do
it innately but instead
have to imprint, early on,
after encountering them.
OK, let's get going again.
Let's see.
First off, thanks to
the wonders of Wikipedia
never being that far away
from us, we now know-- here
were Charles Darwin's parents,
who were third cousins.
And then Charles Darwin
married his first cousin.
So there you have it--
something or other.
But this apparently was
rather common at the time.
And is not quite the optimal,
according to Martha McClintock.
OK.
So, pushing on.
So we've now seen
why you would want
to recognize your
relatives and recognize
the degree of relatedness.
All of our models of who to
compete with, who to mate with,
who to nurse, who
to take care of,
who to be voyeuristic about.
And we've seen the
first domain where
you can do that, which is to
recognize somebody innately.
And one very confusing
aspect of it,
which I managed
to make confusing,
is-- so, what's
up with olfaction
with that and oxytocin and
vasopressin and prolactin?
OK, as follows.
It is innate that you will have
receptors, olfactory receptors,
in your olfactory neurons,
in your olfactory bulb--
in your nose.
It is innate that you will
have olfactory receptors that
will be able to detect
degree of relatedness--
how close an olfactory
signature is to your own.
That is innate.
That will be there.
What appears to be the case
is, oxytocin and vasopressin
make you more likely to make
those receptors-- increase
the number of those receptors.
So this is not oxytocin and
vasopressin making you suddenly
be able to recognize relatives.
It's just making
you better at doing
that-- more sensitized to it.
So that you have 100
receptors reporting instead
of 10 of them-- more accuracy.
What prolactin appears
to be doing is--
and this is under study,
but the best bet is,
this is another way of getting
more of these olfactory
receptors online,
right around birth,
to innately recognize
your relative.
And this time, instead
of making neurons
make more copies
of the receptors,
it's making more neurons.
There's going to be
more subtlety than that.
But broadly, those
are two different ways
of making you better
at doing something
that is innate in you.
Rather than making you suddenly
able to learn how to do this.
So we now transition
to the second way
in which relatives
are recognized,
where it's not innate.
It requires imprinting.
It requires some sort
of learning which leaves
a long-lasting message of it.
Imprinting.
So now we've got imprinting in
yet another use of the word.
And major use of it
coming next Monday.
Imprinting-- how an animal
learns who its mother is.
How a mother learns
who its babies are.
How it imprints on the
smell, on the sound,
on the whatever of its
offspring or parent--
how that learning goes on.
What is clear is,
that's a case where
the learning that the learning
occurs at that point is innate.
What is learned is experiential.
Important sort of
distinction, there.
OK.
So, what goes on with this?
So in lots of species,
you learn the sound
of your infant's voice.
In lots of species,
you learn the odor.
In lots of species, you
learn what they look like.
Different species, different
modalities that dominate.
What goes into, for
example, learning what
your offspring smells like?
Remember, it's not
innate in these cases.
For example, a goat, a sheep--
whatever-- they do not innately
have the means of
recognizing, oh, this
is somebody whose major
histocompatibility proteins are
fairly similar to mine.
In fact, they
share 50% homology.
Oh, this must be my child.
That's not done that way.
These are not innate cases.
So what sort of rules
might you have for how
to recognize your offspring?
Here's a simple one.
OK, there's a whole
bunch of babies out here,
and which ones are mine?
And I'm a goat
trying to figure out
which one I'm going to nurse.
What would be a good
rule that is not innate,
instead building on learning
something at that point?
I know-- I'm going to start
taking care of whichever kid
there smells like
my vaginal fluids.
That's a pretty reliable
way of figuring out
this is somebody you
just gave birth to.
Or, this is someone who I lick
as they're first coming out.
And, for a while afterward, I
figure out, who am I nice to?
Someone who smells
like my saliva.
Someone who I scent-mark
right after this
is someone who smells
like my whatever
glands I'm using, there.
This is someone who smells
like my amniotic fluid.
This is someone who,
after I get that learned,
I then nurse them for the first
time-- this is someone whose
mouth smells like my milk.
You could see,
now, in this case,
it is learning
being built on top
of whatever your own
recognition system is of smell.
You can have
elaborations on this.
How do you recognize a
sibling in species where it is
learned in this imprinting way?
Oh, I'm going to imprint as
a relative on somebody who
smells just like mom.
Somebody who smells like mom's
vaginal fluid or her saliva
or any of that same
stuff going on, there.
Or, I'm going to be nice to
someone who smells like someone
I mated with back when.
That's another strategy
in various species.
You could begin to
see how all of these
are ways of just getting
logical information.
Someone who has the
voice like someone
who I heard peeping when they
were still inside the egg.
Oh, it's them!
I'm going to nurse-- no,
I'm not going to nurse them,
I'm going to give them worms
or whatever it is birds do.
But all these ways of
using sensory information
to say, oh, that's the one!
That's the one.
That's how I know it's them.
So, all sorts of ways in
which this could be done.
How can you prove that this
is not hardwired-- this is not
absolutely dominating?
A technique we've been hearing
about already, which is
that cross-fostering business.
Which is, you take
newborn whatevers,
and you switch mothers
on them, and the mothers
will take care of them.
What does that tell you?
It means other attributes
of these pups coming over
to them-- these rat pups--
override the fact-- wait,
these kids don't smell
like my vaginal fluid!
Wow, they're cute, though, and
there's no other moms around,
and they sure look cuddly, and--
So maybe it takes you 10 seconds
to decide, this is one of mine,
instead of three seconds.
You have different things
being played out, there.
Contrasting sort of
signals coming through.
So that's another
domain of doing that.
So now we move to us and how
we do recognizing relatives.
And initially what
the answer seems to be
is that we have a
different version of it.
We do not recognize
relatives innately,
nor do we recognize
relatives by imprinting.
We don't do that deal of, like,
we smell our parents right
after they're born, or we
sniff the vaginal fluid
and that's how we know who
mom is forever after, or stuff
like that.
So we don't-- instead,
what do we do?
We do it cognitively.
We figure it out.
We think about it.
We think about it, with active,
conscious, cognitive rules
of how you know a relative is.
And, of course, what
we're going to see shortly
is, that's not really how
it works, a lot of the time.
But, for a first pass,
we do it cognitively.
So now you do it--
Instead of, this is
someone who smells just
like my vaginal fluid, the
way the goats are doing,
or, this is someone who I
innately recognize as my child,
the way the rats are
doing it, you're saying,
well, that's the baby
I just gave birth to,
because they haven't taken
him out of the room yet.
So that must be-- a
cognitive strategy.
How do I know who the father is?
Not because I can
smell in the baby's 50%
sharing their major
histocompatibility gene.
This is the only
person I had sex
with during the cycle
that I conceived.
A cognitive strategy.
This is what humans
do, again, [INAUDIBLE]
because we can think.
We can go through
stuff like that.
We can also do other
versions of it,
which is, well, this is someone
who I saw mom give birth to.
Or at least when they
took me out of the room,
and then they, like, gave me
some stuffed animals to keep me
from, like, getting too upset.
And then they said, here's
your new baby whatever.
Oh, OK.
Which is a variant
on, this is someone
who's been around ever
since I saw mom give birth
to that individual.
This is someone
who looks like me.
This is someone who looks
like a family member.
All of these cognitive
strategies, going into that.
We think about it.
We think about it.
And, it turns out, we
have brain mechanisms that
are good for doing that, too.
But we're not the
only species that
thinks about it in that way.
For example, baboons-- wonderful
study, a few years ago.
Baboons can do this with some
sort of statistical thinking.
OK, baboons are polygamous.
Females will mate with a
bunch of different males
during her cycle, and conceive,
and thus it's not at all clear
who the father is.
But everybody there
plays a guessing game.
And everybody does
some statistics.
The usual rule
is, baboons, being
a highly tournament
species-- males do
no parental care of offspring.
Turns out that's
not quite the case.
Some males do.
When they're pretty
sure who their kid is.
And here's how it's done.
You are a baboon, and you
are just hitting puberty.
You're female.
And what goes on is, for, like,
your first half dozen cycles,
you're cycling but you're
probably not ovulating yet.
You're not quite fertile.
This happens in humans, as well.
And none of the big,
high-ranking guys
are terribly interested in you,
probably because you're not
pumping out a whole lot of
interesting pheromones yet.
So who do you wind up with?
You wind up with some poor,
like, adolescent schnook
who has no chance to
mate with anybody else.
And nobody's
contesting his ability
to have a consortship with you.
So you do all of
your mating with him.
The vast majority of the
time, they're not fertile,
because you're not really ov--
Every now and then,
though, you get
this, like,
junior-high-school baboon
guy who gets his
girlfriend pregnant,
and he's the only one.
And what tends to happen then
is, when she gives birth,
he gives a fair amount of
parental care to the offspring.
So what does he have
as a rule, there?
If I'm the only one
who mated with her--
if they're using a
cognitive strategy-- then
I'll take care of the
kid to some extent.
And it is a sight to
behold, how incredibly inept
an adolescent male
baboon is when
he's trying to be paternal.
But what you wind
up seeing there is,
well, maybe he's imprinted.
Maybe he's doing major
histocompatibility gene innate
stuff.
Or maybe he's actually thinking,
hey, I was with her 24/7,
so it's gotta be me.
I'll take care of the kid.
Now you see the more
complicated circumstance,
where it's a more desirable
female-- more mature one--
where there will be a
bunch of males contesting.
And what you will tend to
see is, two days before
and after she ovulates, she'll
be mating with number 10.
A day before and after,
she's mating with number 3.
The day of ovulation,
she's mating with number 1.
That tends to be the pattern.
Stay tuned.
It doesn't fit that perfectly,
because female baboons also
have some opinions about
who they want to mate with.
But, nonetheless,
there winds up being
this pattern, just like that.
So there winds up
being this pattern.
And thus-- you're
the male, afterward,
when she gives birth, and
you're trying to decide,
is this my kid?
Or, should I give some
male parental investment?
And what is shown is,
baboon males do statistics.
They do probability.
What they do is, if
this was a male who
was mating during her
prime ovulatory day,
he is more likely to
take care of the kid
than a male who was
mating during this window
or this window.
They are playing probability.
They're not very good
at it-- no surprise.
But nonetheless this
pattern emerges.
That's not innate recognition.
That's not innate
recognition of some smell.
That's just thinking through it.
Was I with her?
Yeah, but she sure smelled
a lot better the day after,
and that other guy
was with her, so I
guess I'm in this category.
OK, well, I'll smile at the
kid now and then tell him I
like their piano playing.
But I'm not going to,
like, invest anything--
kind of stuff, there.
Here, you see a conscious,
cognitive strategy.
So, OK, so us and other
smart beasties like primates.
Here's another version of it,
occurring in fish-- in sunfish.
And this was research
done by that guy
David Sloan Wilson, that
multilevel-selection-evolution
evolution guy, who actually
has done research in, like,
so many different fields.
Incredibly creative guy.
Here's a study that he did.
Sunfish males,
surprisingly, are quite
paternal in their taking care
of their eventual offspring.
They're almost as
good as Nemo's dad.
And what you've got there
is, in this version, he--
I'm not going to
draw fish mating.
Forget that!
OK.
So the guy mates
with the female,
and she eventually
gives birth to kids.
And he helps take care of them.
Now, instead, he
mates with a female--
and you, the savagely
heartless researcher,
puts him in the next
tank over, where
he can see what's happening.
And you fiendishly,
at that point,
drop down a clear plastic
box right next to the female,
with another male in there!
In reality, he's not
mating with the female,
but he's right there.
And this guy, who's stuck on
the other side of the barrier
and going out of his mind
with jealousy and petulance
and all of that immature stuff.
And what happens is,
after she eventually
gives birth, she-- this
apparently being the female,
in this diagram.
After she gives birth, he
doesn't take care of the kids
as much.
There is no difference in
any of the sensory cues.
Because he, in fact, is
the only one who mated.
This one is kept inside.
There is some sort of cognitive
stuff even going on in a fish.
Remarkable.
So it's not just us.
So we've got this broad
realm-- innate strategies.
One's on very all-or-none
sensory imprinting.
And then there's the folks
who think through it.
We're in the mainstream of that,
but we're not the only ones.
So how do our brains do that?
There is a part of the human
cortex called the "fusiform
cortex."
And what it's good at
is recognizing faces,
which is a remarkable thing.
It specializes in recognizing
faces, facial expression,
degree of relatedness.
You show someone a good
portrait of someone else,
and you will get that
part of the brain
to activate as if
it was their face.
You show a good
cartoon of somebody.
It will do the same thing,
maybe with a little bit
less confidence.
This is the specialized
part of the cortex
that does facial recognition.
Remarkable.
You look at people with autism,
and this part of the cortex
doesn't do a whole lot.
You show a
nonautistic individual
a picture of a
well-known loved one.
Fusiform cortex
activates a whole lot.
You show them a
picture of someone
they don't know a whole lot.
It activates somewhat
to a lesser degree.
You show them a
picture of an armchair.
Doesn't do anything at all.
You take someone who is
autistic, and you show them,
and you get the same low-degree
activation for all three.
You know, mother equals
stranger equals armchair.
This in some ways is the
core of what autism is about.
You see that going on, as played
out in this part of the cortex.
So that's really interesting.
And then it turns out we're
not the only species that
has this specialized
fusiform cortex.
Primates have this, as
well-- nonhuman primates.
Sheep have it, it turns out.
Pigeons who could recognize
pictures of each other.
And why they would want
to do that, god knows.
But pigeons have a very proto
version of the fusiform cortex.
This seems to be
part of what goes
into this conscious, cognitive
strategizing of, this
is a face, this is
a face I've seen
a whole lot more over the years.
So this activates a lot more.
This seems to suggest some
sort of cortical specialization
for recognizing individuals.
More features of
how humans do it.
Something that humans
are very good at,
if they are human
mothers, is recognizing
the smell of their
baby right after birth.
And this has been shown to
have a major histocompatibility
component to it.
In other words, that's not
a purely cognitive strategy.
There's some innate,
instinctual olfactory
signaling going on there.
So, a first bit of
evidence is that we are not
just purely rational
beasts at figuring out
who we're related to.
Babies, very
shortly after birth,
are already spectacularly good
at distinguishing the smell
of Mom versus somebody else.
How do you tell
that with a baby?
You take a newborn baby, and you
give them, like, on this side,
some armpit smell of Mom, and
there's some armpit smell of,
you know-- I don't
know-- Margaret Thatcher.
And what you see, then, is
that the baby, the newborn,
is more likely-- will
spend more time turning
its head towards Mom's smell.
That's how you know it.
Newborn babies cannot
distinguish between the smell
of Dad and any other male.
It's not instinctual,
in that case.
Newborn humans are doing some
version of proximity to mom,
vaginal fluid smell-- whatever.
This seems to be bringing
up a question of,
is there a difference in
bonding in those early stages
between vaginal-birth
offspring and cesareans?
I don't know, but that suggests
that should be happening.
And maybe I should
even find that out.
OK.
Other features of it.
Newborn kids, as we already
know from a couple lectures ago,
can recognize the voice of Mom.
How?
From all that resonance, there,
inside the amniotic fluid,
as Mom reads them War and Peace.
And, as we also
heard, they can't
recognize the voice of Dad.
Not instinctual.
In this case,
getting information
on the sensory route--
the amniotic environment
as a good resonator
for Mom's voice.
So we're now already
getting a mixture, here,
of some instinctual
olfactory stuff,
major-histocompatibility-complex
stuff, some acquired,
hardwired sensory-driven stuff.
Ooh, does this sound like the
person whose voice I heard
for those last nine months?
And then some cognitive
stuff-- trying to figure out
who this relative is.
Ooh, who did they come
with to the party with?
All of that-- the
cognitive stuff.
So, already a suggestion
that we're not just
such pure cognitive machines.
So where is that
most interesting?
And this is in a totally
fascinating series
of studies that were
done over the years,
showing just how little
conscious cognition might
play out in us humans in
some really critical realms.
Which is, who you decide you
are interested in mating with.
OK, so how does
that work in humans?
All sorts of different ways.
But here's one way in which
it does something interesting.
And this was a classic study
done by an anthropologist named
Joseph Schaeffer.
And this is what he did.
He studied people who grew
up in Israel on kibbutzes.
Kibbutzes-- these are these
traditional, socialist sort
of communes, where one
of the-- none of them
are like this anymore.
But one of the early
principles was, one parent
is as good as another parent.
All the kids are raised in
these big, communal bathtubs
together.
And it's one big, sort
of socialist [INAUDIBLE]
of everybody bathing
naked together.
And what Schaeffer found was
this very interesting thing.
Which is, you are brought
up in your age group.
All the kids born
this year are raised
in the same communal group.
And they take their
baths together,
and they play
together, and they've
got the same-- one
parent takes all of them
for one afternoon,
every Tuesday afternoon,
and the next one comes
for the next shift.
And this big communal
business, there.
And what Schaeffer
discovered was,
if you were raised in the
same age group as somebody,
anywhere up to six
years of age, you never,
ever wind up marrying them.
And this was not with a sample--
an appropriate sampling.
This was a study he did of every
individual who ever grew up
in the kibbutz system in Israel.
We appear to have
a rule as follows.
If this is somebody who you
spent a whole lot of time
with before six
years of age, this
is someone who you
sure don't want
to grow up and marry-- yuck!
And you love them--
they're incred--
but they feel like my sister.
They feel like my brother.
Whoa, that would be
totally grotesque!
There has never been a
case of people brought
up during the first-- grow up
in your first six years of life,
taking a whole lot of
baths with someone,
and you are not going to
discover an amorous passion
for them when
you're 20 years old.
They're going to feel
like a sibling for you,
for the rest of your life.
What is that telling us?
We have a very noncognitive
strategy in there.
Yes, who are relatives--
who are appropriate people
to mate with?
Well, if we know that this is
the daughter of Mom's sister,
then this person
is not appropriate,
and this whole cognitive--
spend a whole lot of time
naked with somebody, taking
baths and playing pattycake
and counting their toes,
the first six years of life,
they feel like a sibling.
Something very similar was
then shown by Arthur Wolf,
here, in the
Anthropology department--
a different cultural version.
Traditional Taiwanese
marriages, where
there's some equivalent of that,
and where either you wind up
with your future spouse
at some insanely early age
and basically get brought
up with them from infancy,
or it happens later.
And if you're brought up
from infancy with them,
you have a disastrous
marriage later on,
because they feel like a sibling
for the rest of your life.
So what this shows
us here is, yes, we
are these wonderful,
rational, cognitive machines.
We've got all sorts
of innate strategies
and sensory-imprinting stuff
going on, instead, in us.
We are not a whole lot
fancier than hamsters.
What does this set us up for?
A topic that's going to
be real important when
we come to the lectures on
aggression and cooperation
and competition and all of that.
Which is, if we spend a lot
of our time figuring out
who we are related
to-- cognitively--
or, even more
importantly, if we are
malleable in the way these
kids growing up in Taiwan,
or in these
kibbutzes-- if we are
malleable in who
we feel related to,
it is possible to manipulate
us in lots of ways
to feel more related
to individuals
than we actually are, or to feel
less related to individuals.
And the terms for these
are "pseudo kinship"
and "pseudo speciation."
And what we will
eventually see is,
when you make sense of human
violence and human cooperation
and human aggression
and all of that,
we are so easily manipulated
as to who counts as an "us"
and who counts as a "them."
And one of the brilliant things
militaries all the world over
do, whether you're talking
about clans with warrior classes
all the way up to sort
of state militaries--
what you see in all these cases
is a brilliant understanding
of how to make nonrelatives feel
like they're a band of brothers
and how to make "them" seem
so different they hardly
even count as humans.
So this ability for
us to be manipulated
in these subliminal ways, as
to who counts as a relative,
will come back to
haunt us big-time
in making sense of a lot
of human social behavior.
In other words, we are
not purely rational.
OK.
So what we will do on Monday
is switch another bucket, now,
to this field of ethology,
which, once again, is trying
to make sense of, what
behaviors are hardwired,
what does environment do?
You will see a completely
different approach--
For more, please visit
us at stanford.edu.
