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>>BUSS: Well thank you very much for that wonderful introduction and for coming to this
talk. It's a delight to be here, and to talk to you about evolutionary psychology, why
students love it, how to teach it.
I've been teaching evolutionary psychology, myself, for many, many years, starting at
Harvard and then for a number of years at Michigan, and most recently at Texas. And,
so, because I teach it every year, and I love teaching it, I'm always struggling to devise
different tools that will enable students to understand the logic of both evolutionary
theory and evolutionary psychology, with greater clarity, greater depth. And it's a challenging
thing to do because some of the concepts, even though evolutionary theory, in its simplest
form, is a fairly simple theory, straight forward, shouldn't be all that complicated
to understand, it turns out there are a number of complications, a number of cognitive biases,
even perhaps evolved cognitive biases that interfere with our understanding of evolutionary
theory and its application to humans.
And so, what I'd like to do today is to share with you just some of the tools that I've
developed in concert with colleagues that I've found useful in my teaching of the topic
of evolutionary psychology to a variety of different audiences.
Now, of course, evolutionary psychology goes back to Charles Darwin. I view Charles Darwin
as the first evolutionary psychologist for this prophesy, if you will, at the end of
his 1859 classic book, "On the Origin of Species." He said, "In the distant future . . . psychology
will be based on a new foundation, that of the necessary acquirement of each mental power
and capacity by gradation."
Let me see if I can put that up here. Is that going to work? Okay. Cool. Thank you.
Darwin envisioned his theory of evolution as applying to humans. Humans were not exempt
from it, but, of course in that first book about evolutionary theory he just eluded to
humans at the very, very end. He knew his theory would be very controversial, knew it
would deeply upset his wife, and his colleagues and so, but was, in essence, a forecast that,
yes, humans were not exempt from the causal process of evolution by selection as it shaped
our psychological mechanisms.
Now, one of the challenges that I have found is conveying the notion of "deep time". Most
undergraduates, for example, when you say, "Think of something really old," they'll say,
"Well, you know, there was this band called The Beatles, you know, and they're really
old, you know." But they don't think in "deep time", and, in fact, if you think about it,
our evolved psychological mechanisms were not designed to think in "deep time"; to think
in small increments gradually over thousands or millions of generations.
The adaptive problems that humans had to solve and have to solve are in very tiny time increments.
So an eye blink reflex to avoid a bug flying in your eye, how to keep warm, how to get
food for your belly, how to attract a mate, how to build a coalition, how to avoid social
conflict, how to cooperate with people, okay, these are all adaptive problems that occur
in very short time intervals; and so we really were not designed to think in time spans of
thousands or millions of years.
And so it's quite a challenge, so I have a number of exercises, such as things like looking
at the current evidence for successive migrations out of Africa. The first one being about 1.8
million years ago, and there have been successive migrations. And, practically every week, if
you read the New York Times they discover something like an artifact present somewhere
in Africa. The most recent on is something like 44,000 years ago that demonstrates that,
yes, modern humans did evolve in Africa and then migrated out, and brought with them various
capacities, including the capacity for culture.
You can talk about the evolution of brain size, which occurred over millions of years,
going from 500 cubic centimeters to our current brain size which is roughly three times that
size, roughly 1350 cubic centimeters.
Sometimes I talk about milestones in human evolutionary history; go back to when placentals
evolved; when did mammals make their first appearance; what about primates, etc. Different
landmarks in the evolution of humans. And in my textbook, "Evolutionary Psychology,"
I have a table that starts with the origin of life, about 3 ½ billion years ago, and
then talks about successive landmarks. And these are just tools for getting students
to understand "deep time". That things occur on time spans, not just like The Beatles or
last year's boy band, but rather in spans of millions of years.
Okay, a second has to do with the fact that there are multiple levels of causation, multiple
of explanation. Now, we know that as teachers, but students don't often appreciate that.
And there's a story that I use to illustrate this, and I call it the turtle story. And
that is that, and I don't know if it's apocryphal or not, but in the old days when professors
lived in caves, the student came up to the cave door, knocked on the door, and had a
question that he wanted to pose to the professor. He said to the professor, "On what does the
Earth rest?"
And the professor thought for a moment. He said, "The Earth rests on the back of a giant
tortoise."
And so the student nodded, walked away, but was still puzzles. Came back the next day,
knocked on the cave door and said, "But on what does that turtle rest?"
And the professor thought, and he said, "On the back of an even larger tortoise."
So the student walked away again. The third day the professor sees the student coming
up over the hill, toward the cave, waves the student away, saying, "It's turtles all the
way down."
Well, there are turtles all the way down, in some sense. There are multiple levels of
explanation, and the thrust of the student's questions were very apt. That is, a search
for deeper, and deeper, and deeper causal explanations for a phenomena.
So, in this particular slide, we want to understand here human behavior, ultimately, but that
behavior rests on a foundation of underlying psychological mechanisms, which I'm going
to talk about a little bit more. But, we also have a physiology, a neurology, a genetics,
and evolutionary processes which created the human form that we see today.
A third, is that I confront the three theories that are extant to explain the origins of
complex adaptive mechanisms. Now the one, of course, and I teach in Texas so this can
get to be a sensitive issue, is creationism. Okay, the notion that a supreme deity created
humans and all other organisms and all the adaptive mechanisms that those organisms contain,
and whatever he created is simply what he created.
A second theory is what I call seeding theory; the notion that extraterrestrial organisms
came down to Earth and planted the seeds of life, and then, perhaps, evolutionary processes
then took over, and we evolved into the state that we are today. And there are some adherence
to seeding theory.
The third is evolution by natural selection. Now, how do we deal with these kinds of things?
Now, I teach in Texas and, so, there are a lot of people who do believe in creationists
explanations. Okay, the way that I deal with this, and it can be a sensitive issue, but
I haven't had any problems with it, is simply by reference to the scientific utility of
the different theories.
So, if we go back, look at creationism, well, it may be true. It may be true that a supreme
deity created the forms of life and the adaptive mechanisms that we see today, but, from a
scientific perspective, it's not a terribly useful theory. That is, it doesn't lead to
new empirical discoveries. It doesn't have heuristic value that we value in scientific
theories. Whatever exists is simply what that deity created. And, so, as a scientific theory,
although it might be correct, it's not terribly useful for us.
Seeding theory might also be true. And every now and then you read the paper, usually they're
in the tabloids, National Enquirer, you know, UFOs, extraterrestrial scene spotted, you
know, there's evidence for them in the farm fields, and I'm sure you've seen them all.
And, perhaps that's true too, but it is again, not a very useful theory. It simply pushes
the causal question back one step to what created, what causal process created those
extraterrestrial organisms, and then what causal process took those seeds that they
planted and then transformed them into the organisms that we see today.
So, we're basically left with the theory of evolution by selection in its modern form.
And, there have been different evolutions of evolutionary theory, so to speak, since
Darwin's time, since he didn't, in his time, of course, he know about genes and differential
genic selection. But one of the interesting things is, is that some interesting work that's
been done by Dr. Christine Legare and her colleagues, is that it turns out that adults
can hold both evolutionary and supernatural explanations in mind at the same time. Okay,
that is, they can believe both in a supernatural explanation, a theistic explanation, as well
as believing the causal process of evolution by selection. And so it's not the case that
as people grew up into adults they relinquish their supernatural beliefs, but, it turns
out, we are cognitively capable of holding in mind at the same time.
Now, of course, it's essential to explain, if students are going to understand evolutionary
psychology, they have to understand the logic of natural selection. And, to do that, it's
important, I've found, or useful to talk about things that were known before Darwin even
came on the scene. Okay, that is it was known that, or believed by some scientists that
change took place in organic structures over time. That is, there was evolution.
Evolution simply means change over time. That's all the word means. And, so, if you actually
phrase it that way it loses some of its, you know, controversial nature. It's just simply
change over time, and we're just saying [unclear] what causal processes are responsible for
that change over time.
It was also know before Darwin's time that characteristics of organisms seemed to have
a purpose. There was an apparent purpose to these. So the quills of the porcupine seemed
to be a defense mechanism against predators. The hard shells of the turtles, the nasty
scents of the skunk, you know, these seemed to have a purpose. They seemed to have a function.
And so these were observations before Darwin came along the scene.
Now, what was his challenge? The explanatory challenge of Darwin was really momentous when
you think about it. Okay, he had to explain why change took place, he had to explain how
new species emerged, and he had to explain the functions of the component parts of these
different species. So that's a pretty hefty challenge, and the theory that could do all
these things is a pretty important theory. And as Dan Dennett said in his book, Darwin's
Dangerous Idea, it's about the most important scientific idea that anyone's ever had.
Now, of course, it's, as I said, fairly simple in its fundamental form, but it's fascinating
to me that in the history of science it wasn't discovered until, well approximately, 1859
or perhaps 20 years before that when Darwin first came upon it. He talked about publication
lag. Darwin was the king of publication lag.
So, what are its ingredients? Basically it requires three ingredients. There has to be
variation. Okay, so individual differences – some of those individual differences have
to be heritable. Okay, so if you, you know, one example that I use is if you take a plant
and a can of paint, and you paint the leaves pink, will the next generation of plants have
pink leaves? Well, no they won't. This is an acquired characteristic and so acquired
characteristics are not passed down. And there has to be differential reproduction by virtue
of those heritable variants.
So variation inheritances, and differential reproduction – everyone in this room came
from a long an unbroken line of ancestors, and if at any one point in that time, if any
of our ancestors had failed to reproduce, and broken that chain, that inviolate chain,
no one, you would not be here and I would not be here to discuss this very issue. So
we are all descendants, but not all of us will become ancestors. And so each generation,
each next generation is a bit different from the parental generation – what Darwin called
descent with modification.
And so his theory of evolution did a remarkable job. It explained these three things. It explained
descent with modification, or change over time, due to differential reproduction by
virtue of those heritable variants, those variants that contribute to survival or contribute
to reproductive success, as we now know it. Those got passed on in greater numbers. Qualities
that failed to contribute to survival or reproductive success basically bit the evolutionary dust.
They failed to get passed on in greater numbers. And so you see descent with modification or
change over time as a result of this causal process.
It explained the apparent purpose of quality of the component parts. Okay, that is the
function of a mechanism, the function an adaptation is the manner in which it contributes to a
problem of survival or a problem of reproduction. Okay, and that's what we refer to as an adaptive
function, the apparent purpose of quality. And also, kind of remarkably, it united all
species into one grand tree of descent. That is, we are related to not just other primate
species, but all other mammalian species, and all species going back to the origin of
life 3 ½ billion years ago. So, it's a pretty remarkable feat to have a theory that can
do all those things, and Darwin's theory did that.
Okay, but there was a problem, or rather a couple problems. Darwin was an amazing scientist
in this respect, and I try to teach this to my students; he noticed that he had a habit
of forgetting facts that were inconsistent with his theory. Something I know that I and
my colleagues are particularly prone to. Scientists do that. They are very fond of their theories.
And so Darwin created a special notebook where he forced himself to write down those facts
that were inconsistent with his theory, because they troubled him, and he wanted to deal with
them.
Okay, one is the well-known peacock. You know, and he asked, "How could this weird, brilliant
plumage possibly have evolved?" This cumbersome structure is metabolically expensive and it's
bad for survival. It's like a neon sign to predators advertising fast food. Okay, how
could this weird structure possibly have evolved? Darwin even wrote in his notebooks, or in
private correspondence, [unclear] he said, "The sight of a peacock gives me nightmares."
He also noted other puzzling phenomena. *** dimorphism was one of them: differences in
the size, shape, morphology, of males and females of same species. And his logic was
as follows: both sexes face the same survival problem; both sexes have to eat; both sexes,
if they are warm blooded, have to thermo regulate; they have to fend of predators. Why would
the sexes differ in size/shape/morphology at all given that they face the same survival
problems?
Furthermore, why would some species be extremely sexually dimorphic, like these sea lions down
here. I don't know if you can see that well, but the male sea lion weigh, on average, 4000
pounds, female sea lions weigh, on average, 1000 pounds, so there's a 4-1 ratio. And the
mating patterns of these beasts are really quite amazing to watch. If you are interested
you can watch they are [unclear] 50 miles south of Palo Alto on the beach in Northern
California [unclear].
And in mating seasons, basically the males go at it. They have these huge tusks, and
these 4000 pound animals pound and attack each other. They have a system known as harem
polygyny where, basically, the victor of these same sex competitions in the elephant seals
gets access to a haram of about 20 females.
And I know that some males in the room might think, "Well, that sounds like a pretty good
deal," but, it's actually not, because it's extremely difficult for the male to maintain
access to the harem to start with, because those males who are deposed are not happy
about it. Okay, so they try to do what we call "mate poaching". They try to copulate
with the females when the alpha male is not looking, and then the females don't like that.
They emit a bellow, the alpha male comes bounding toward them, beats them up, but then there's
another poacher on the other side of the harem, he has to bound over there. It's so exhausting
that a male can maintain alpha status for only a season or two, and then you see him
tired, exhausted, with wounds, kind of lying there, just barely breathing, on the beach.
So I don't recommend it as a mating strategy.
Back to the central point. Okay, the issue is this: what causal process could explain
this, like the brilliant plumage of peacocks; what causal process could explain *** dimorphism;
but also what causal process could explain variation across species in the magnitude
of *** dimorphism? So you have some species, such as the elephant seals, or sea lions,
that are extremely dimorphic. You have – these are hamadryas baboons that are moderately
dimorphic; males are about twice the size of the females. And then you have humans who
are even less dimorphic; males are about 8-12% taller than females, on average, although
it depends on what aspect of bodily dimorphism you examine. So upper body strength shows
much greater *** dimorphism in humans, than does height. But none the less, and then
you see some species like gibbons, a primate species where the males are virtually indistinguishable.
So, these were puzzles that Darwin wanted to explain. And he explained them, and his
nightmares went away when he came up with the theory of *** selection.
*** selection deals with not with the evolution of characteristics because of the survival
advantage that they gave organisms, but rather by virtue of the reproductive, or more specifically,
the mating advantage that they gave organisms.
So he explained this by giving two brilliant, simple, but powerful causal processes. The
first is intersexual selection, or preferential mate choice. And the logic is as follows:
this is "what we're looking for" from the perspective of the female [unclear]. How many
females would prefer this guy [indicating overweight man]? [audience laughs] Just a
raise your hands. [audience laughs] I'm not getting no takers.
Well, the logic is this: Okay, if it is the case that there is some consensus among females;
if there's some agreement about what qualities are desired in potential mates, and those
desired qualities have some heritable component, then, over time, what you will see is those
males who have those desired qualities are preferentially chosen; those lacking the desired
qualities basically get shunned and excluded, rejected from mating. And so you see change
over time that is an increase in the frequency of qualities that are chosen by females. Okay,
preferential mate choice.
Darwin observed that throughout the animal kingdom females of many species, most species
that he observed, seemed to be more choosey, seemed to be more discriminating, seemed to
be more discerning about who they would mate with, and so Darwin actually coined the term
"female choice" to describe this process.
Most biologists at the time dismissed it out of hand. They thought it was absurd that the
evolution of species could possibly be under the influence of female control.
The other component is also very, so this is a simple process [unclear] but it's very
powerful in its implications. So what it means is, basically, all you need is those ingredients:
consensus, some heritability of that consensus, that is some heritability of desired qualities,
and then that iterated over time, and you will see evolution that is change over time.
So, if it were the case, for example, that all women preferred to mate with males who
had red hair, then this room would be ablaze with redheads. In looking around, I see that
is not the case. So there are a few redheads, but clearly it has not been the dominant preference,
but you see the logic of it.
The second causal process of *** selection is intrasexual competition. And that deals
with the sea lions that I mentioned. These are stereotypical examples of intrasexual
competition. Again, logic very simple, very easy to convey, and exists in, basically,
all sexually reproducing species. Okay, and, so in the stereotypical example two male stags
lock horns in combat, victor gains *** access to the female, looser ambles off with
a broken antler, very dejected, with low self-esteem, needing psychotherapy.
But whatever qualities lead to success in these same sex battles, those qualities get
passed on in greater numbers. Qualities associated with loss basically, again, bite the evolutionary
dust. They fail to get passed on.
And so, now in some species it could be things like size, strength, muscle mass, athletic
agility. But the logic of intrasexual competition is more general than that. So in our species,
for example, although we sometimes engage in intrasexual competition, I don't see it
all that much; what biologists call "contest competition", this physical combat. We don't
see it that much. I don't see it on my University of Texas college campus too much. Occasionally
a fight breaks out, but that's not the main ways in which males compete with each other,
or the ways in which females compete with each other for access to mates.
So, in our species, for example, we compete in position in status hierarchies. Status
hierarchies are universal across human groups, formal/informal. Position hierarchal status
is linked with access to greater resources, and access to more, and more desirable potential
mates.
And so, in principal, intrasexual competitors need not even meet, in order to compete. So
there are different forms of intrasexual competition: hierarchy negotiation, something called scramble
competition, and so forth. But you see the logic. So, again, whatever qualities that
are linked with success in intrasexual competition, those qualities can affect change over time;
that is evolution.
Okay, this is still all very old hat. It goes all the way back to Darwin, 1871, his second
major book on the topic where he does deal with humans. Biologists, as I mentioned, at
the time, said that Charles, or Chuck, or I don't know if they called him Chuck, but
Charles, we'll go along with you on the natural selection. We can see survival, but this notion
of females having choice – totally absurd.
And so the theory of *** selection basically was ignored for 100 years. There was a little
flurry of interest with the statistician that you probably are familiar with, R. A. Fisher,
who invented some of the statistical techniques we use today. He was also a geneticist. And
so he developed a very interesting twist on *** selection theory that I don't have
time to go into, known as the "sexy son hypothesis". But basically it wasn't until a century later,
a hundred and one years later, so, 1972 that a graduate student at Harvard University,
Robert Trivers, came up with the theory of parental investment in *** selection. And
so after 100 years of *** selection basically being in eclipse and scoffed at, and laughed
at, and not taken seriously, it has now become one of the most important theories we have
in evolutionary biology, and extremely important, or course, in understanding some of the pattern
of mating that we are seeing in humans and other species today.
So, it's of course important to talk about the core tenets of evolutionary psychology.
Now, so, I've written some papers about these in American Psychologist. Other colleagues
of have written papers: John Tooby, Leda Cosmides, and others. So there are more technical and
detailed papers that you can refer students to. But, just in a nut shell, I think it's
important to understand that some of the basic tenets of evolutionary psychology, so, very
briefly, what are they.
One is that all behavior is an interaction between evolved psychological mechanisms and
input to those mechanisms. So, one example I use is a simple one: the callus producing
mechanism. So, do people, you know, walk around and all of the sudden calluses spring out
of their ears? Okay, no. You get calluses by an environmental event: repeated friction
to your skin. So calluses grow, and they are designed to grow, specifically on those areas
where you've experienced repeated friction. So, if you want to explain why do humans have
calluses and what explains the thickness in distribution within and across species, and
within and across individuals within cultures; I'm sorry not species, with cultures; you
have to understand that there is an environmental input, repeated friction, that activates an
evolved physiological mechanism that is designed to produce new skin cells that then function
to protect the anatomical and physiological structures beneath the skin.
And so, it's fundamentally, and the same thing you can apply, I start out with calluses,
and then I go through some other examples. Jealousy; do people wake up in the morning
insanely sexually jealous? Okay, no. The jealousy, and there's good evidence that human males
and females have jealousy or something like it, as an evolved psychological mechanism.
It gets triggered by specific forms of input. Is your mate displaying cues to infidelity?
Are mate poachers coming and hitting up on your partner? Are there contextual features
that activate possibilities of defection from the relationship, such as a mate value discrepancy
opening up between the two partners? And so, it requires social contextual input before
the adaptation is activated.
So evolutionary psychology is fundamentally an interactionist framework, and, in fact,
it's, in my view, the only cogent interactionist framework we have. So every psychologist in
the world, I'm sure if we polled everyone here at APA, said "Are you an interactionist?"
would say, "Oh yeah, I'm an interactionist". "Do you believe that both environment and
nature/nurture have important things to say about human behavior?" "Oh yeah, I believe
their both [unclear]." But that doesn't help us. It doesn't go very far. We have to specify
the precise manner in which these interactions occur, and understanding psychological mechanisms
does that by identifying the mechanisms, the input that they were designed to take in,
the input they were designed to be sensitive to, whether it be repeated friction or cued
infidelity, that provides us with a powerful interactionist framework that's lacking in
most of the rest of psychology.
Second, all psychological mechanisms, at some basic level of description, originate from
evolutionary processes. So, I was fortunate when I taught at Harvard B. F. Skinner was
also there, and I had a few conversations with him. And if you talk, of course he's
dead now so you can't talk to him, so you'll have to take my word for it; but he said,
and he's actually said this in print as well, that yes he believes that classical conditioning/operant
conditioning, these fundamental laws of learning, he believed that there were these two fundamental
learning processes. Yes, they owe their existence to evolution by selection.
So, even Skinner, the most ardent quote "environmentalist", was an evolutionist as well. He just believed
that the number of mechanisms that we had, including learning mechanisms, were few in
number and highly domain general. Work from a variety of fields has, of course, challenged
that view. We now know that a number of evolved mechanisms is much greater. Even the number
of learning mechanisms - far, far greater than those the Skinner envisioned.
How am I doing on time here? Doing okay? I'm still on teaching tool number three. I better
hurry up here.
But just to take a very quick example. We know that there are specialized learning mechanisms.
For example, in food-aversion learning that even John Garcia demonstrated in the 1960s.
That's different from, say, kin-aversion learning or *** avoidance learning. You have to
learn we're not born knowing who our genetic relatives are, but we have to avoid mating
with them. And so there are *** avoidance learning mechanisms and they turn out to be
very sensitive to who you grow up with, so proximity of individuals and co-residents
while you're growing up turns out to be an important cue that triggers, "This is a member
of my kin". It can result in mistakes sometimes, but that seems to be a reliable cue that it's
sensitive to.
But that mechanism; so you have food-aversion learning, kin/*** avoidance learning, you
have hierarchy negotiation learning. So, what are the criteria in your local culture that
are critical for status and reputation? Okay, and those things also have to be learned,
and if you go to the Aché hunter-gather group in Paraguay, good hunting skills is critical
for status among males in the Aché. Now, it's not, I know, in my psychology department.
So I wouldn't, if I walked into a department meeting and slapped down a deer that I had
just taken down, that will not raise my status among my colleagues, I can guarantee you.
So we have to learn what criteria are relevant to our local group in terms of status and
reputation. So these are just three quick examples: food-aversion, *** avoidance,
and status and reputation. And there are likely many more. And so the key point that I'm making
is that, whatever mechanisms we have, at some basic level of description they owe their
existence to evolution by selection. And so you can run but you cannot hide from evolution
by selection.
Okay, I'm going to very quickly go through this.
There is variation among evolutionary psychologists, but many endorse the view that you can describe
psychological mechanisms as information processing devices, and I think it is very useful to
do so. So as I said with calluses or cues to infidelity as input, we have representations,
procedures, decision rules, internal cognitive mechanisms that process that information and
then ultimately produce some form of output in the form of calluses or behavior. In the
case of the jealousy example, the behavior ranges from vigilance to violent. So, "Do
I start keeping a closer eye on my mate? Do I beat up my intrasexual rival? What is the
relative formidability of that rival compared to myself?" Etcetera.
And so this is a useful way to describe evolved psychological mechanisms. They are, of course,
instantiated in the brain, not in the big toe. I don't probably have to tell you that.
And, critically, they are functional. Okay, and this is something that oddly was scoffed
at in much of the field of psychology. Now, not in William James. If you go back to 1890,
William James, who was an evolutionary psychologist, thought function was extremely important,
but it became unreputable to talk about function.
But, in my view it would be like if let's say you were a medical researcher and let's
say you were a liver specialist. And say, "What is your area of expertise?"
"It's the Liver. That's what my area is."
And I ask you, "Well, what is the function of the liver?"
And you say, "Well, I don't know. I don't care about that. It's not an important question."
Well, you would think there was something very important missing in my understanding
of the liver, if I didn't know what its function was. In this case two: one of it being to
break down toxins, to filter out toxins so that they don't damage your other bodily organs.
The same is true of our psychological mechanisms. We have to understand what their functions
are. So that's a critical and indispensable step in the process.
Ultimate and proximate causation – This is a difficult one to get at. And so, in other
words, what we have to do, and this is related to understanding its evolved function, we
have to understand, ideally we want to understand the phylogeny. That's often very difficult
to do because we don't have a video tape of our evolutionary past so we can't go back
in time. There are a lot of clues, and so there's a certain way in which we can go back
in time. But, nonetheless, we have to ask not only how a mechanism operates, but what
its function is; what's evolved function is.
And so I remember teaching a graduate class at the University of Michigan and I could
not get this distinction across to this one male graduate student [unclear], who you would
think at the University of Michigan there would be very smart graduate students, which
they generally are, but this guy just could not get it. Everyone else in the class got
it. This guy couldn't get it. Finally, in exasperation I asked him, I said, "Why do
you think on average men are taller than women?"
And so he thought for a minute, and he said, "Because they have longer bones."
Well, at that point I gave up. But, in a sense, he was right. He was describing in approximate
sense, yes, if you measure the bones of male and female, and add them all up, there's approximate
sense in which that quote "explains why males are taller". But we find that scientifically
unsatisfying. We really want to push that causal step back; that is what causal process
resulted in males being taller than females on average. And that basically boils down
to the likely ones being *** selection explanation. So, either female choice; females
preferring taller males iterated over time; taller males having a slight advantage in
intrasexual competition; or perhaps something else; that there was a division of labor,
such as hunting, although my Aché anthropology colleague, Kim Hill, tells me that actually
tall hunters have a disadvantage because their too clumsy and their prey animals can see
them coming for a mile away, and so he thinks that short hunters in the Aché have an advantage
enough. Of course he, himself, is quite short and so he might have a bias in that [audience
laughs].
But, the key point is that we want to push that causal step back. We want to understand
why. Okay, and that why question is. And so sometimes I use that long bones explanation
to convey the need to understand ultimate as well as proximate explanations.
Teaching tool 8.
I'm going to have to start speeding up here because I realize I'm going too slowly.
We have to understand that humans were not "designed" to understand the causal process
that created our psychology. I alluded to this earlier in the introduction where I said,
you know, "What are we designed to do?" We were designed to solve adaptive problems in
the here and now. Okay, keep warm, you know, get food, protect your children, you know,
avoid predators, avoid infectious diseased individuals. Okay, these are immediate adaptive
problems, and so our minds are not designed to think in timespans of evolution.
And this is a - Gary Larson is one of my favorite cartoonists. I don't know if you can see this.
This is a man explaining to his son as he's looking at a sparrow. He said, "And now, Randy,
by use of the song, the male sparrow will stake out his territory … an instinct common
in the lower animals." Now, this kind of illustrates - of course they're surrounded by fences displaying
that humans do display territoriality, but he's of course oblivious to that. This is
just an instinct common in the lower animals. And so there's a sense in which we are blind
to our own adaptations.
So, as I said, what is the human mind designed to understand? It turns out even worse than
that because, ironically, we have evolved cognitive biases that actively interfere.
So it's not just that we don't understand. We have biases that interfere with our understanding
of evolutionary processes.
Now again this is work by Dr. Christine Legare and colleagues. And I'll just mention too,
one is essentialism. Okay, that is we believe that species have this internal essence that
is unstable overtime and unchanging in its nature. Now of course this quote "cognitive
bias" is very useful. If you look at a sea turtle, in an individual's life, it is unchanging.
Okay, so turtles aren't evolving very rapidly in our lifetimes. And so the view that turtles
have this underlying internal essence that's stable over time is very useful. But it interferes
with our understanding of evolutionary processes, which are gradual and occur over time.
And so I have Darwin's finches there that show that, you know, there's adaptive specialization.
Change in the shape and morphology of the beaks of different finches on different islands
to correspond to the size and shapes of the nuts that were available on those different
islands.
And so this essentialists biases interferes and also we have a teleological bias. Okay,
and it is again [unclear] it's very useful to attribute desires and motives and intentions
to other people because that helps us to predict their behavior, but it can be misapplied.
So we say like the sun is trying to come out. Well the sun doesn't have a motive to come
out. It's not "trying" to do anything. Right?
So we misapply it and we sometimes misapply it to animals. So why did a giraffe have a
long neck? Well, it's trying to get to the leaves on the top of the tree and so that
straining, you know, that's what explains it. Well, that is not what explains it. Okay,
it's a different causal process. Okay, those giraffes that happen to have a bit longer
necks actually succeeded in getting those taller leafs. With giraffes, as a parenthetical
note, it's actually more complicated than that. There's evidence that giraffe necks
actually play a part in intrasexual competition. They use their heads basically to like whack
the other males and beat them out.
Five mintues? Sheesh. Okay
Moving right along. Use examples from the human body. Okay, liver, lungs, heart, larynx,
callus producing mechanisms, very useful. Use other examples. Animal examples are very
helpful I find, because it's often, even with mating, okay, it's useful. There's a fascinating
literature on insect mating patterns, and insect mating systems, and insect mating adaptations.
And, in fact, my reading of insect mate guarding strategies and adaptations was what led me
to start studying human mate guarding and mate retention strategies. And so, but looking
at other species is helpful because we do have this kind of anthropocentric bias. We
sort of see everything through the lens of our own species. And so, looking at other
species is sometimes helpful in that respect.
Another example. Use examples that relate to student's lives. So mating, cooperation,
aggression, common clinical problems like depression, eating disorders, social conflict.
And it turns out that these topics, which are so central to most sexually reproducing
species, are also central to the lives of students, and students care about them. And
so that gets their attention and it's not random. You know, that they're obsessed with
things like mating, and social conflict, and aggression, and, you know, conflict with parents,
and so forth.
I use thought experiments. And I have a whole list of them, and a few of them are available
on my website, but I'm working on publishing a longer list of what I call thought experiments,
which are basically just ways of getting students to think about things. And one of them I use
is what I call a mission impossible experiment to get across the modern genes eye perspective
on genic selection. And what would you do if you were a gene? You are a gene. Your mission
in life is to replicate; to replicate more successfully than other competing genes. What
would you do if you were a gene? And so students start to think about it. And starting out,
well genes inhabit bodies. They are not just isolated. So maybe you might want to do, for
example, increase the survival of the body that you inhabit. So if you have an effect
that increases the survival of the body then that might help. And go through a few other
things.
So, basically, the three big categories of things; so you increase the survival of your
body, which we call your vehicle. In some sense, you want to make copies of yourself,
so you influence your vehicle to reproduce and that involves doing things like influencing
your vehicle, your body, to find fertile mates, and to do certain things with those fertile
mates, etc. And then also, in terms of modern inclusive fitness, aid the survival and reproduction
of other vehicles that contain copies of yourself; that is genetic is genetic relatives.
Okay, so this thought experiment, getting students to think about it, usually students
come up with the first two. Very rarely, maybe with the exceptional really bright student
will come up with the third, but it really helps them to understand modern evolutionary
theory as we understand it, since the inclusive fitness revolution.
Other things. List all the qualities that women want in a long-term mate. Women go on
for half an hour about this. I fill up five blackboards worth of things women want in
a long-term mate. I ask men – I get about a blackboard and a half and then run out of
ideas. And so the women in the class have to help them. "Well don't you want this? Don't
you want that?" So with women's help we get a bit more.
List all the things that you know that men have done that irritate, anger, annoy, or
upset women. Again, women are very voluble on this topic, and I have 147 different things
you can do to upset a woman, if you want to know them. I have even scaled them by how
upsetting they are.
But these things, these thought experiments, help to get students interested and attending
to the topic, and they really get into these topics.
Surgeon general's warning. Okay, I issue at least three surgeon general's warning. And
that is, for me, life is too short to *** foot around the truth. Okay, so, I just lay
it out there.
First, there are dark sides to human nature. Yes, we are not all, you know what do they
say about girls, you know; and boys, I know, puppy dog tails, and whatever. Girls are all
sweet and fluffy and everything. Well, humans have a dark side to their nature, okay, and
we have adaptations to inflict costs on other humans of various sorts, ranging from physical
violence to other sorts of things, like you know, damaging their reputation, and what's
sometimes called a relational aggression. So be explicit about that.
Yah, no, we are not a purely, wonderful, cooperative species that is corrupted by bad parents and
bad culture and western influence. Okay, yes we do have adaptations for cooperation and
altruism, but we also have these darker elements/cost inflicting elements. Important to be upfront
about that.
*** conflict is prevalent. And, I go over – I have a lot of my own research program
that's devoted to *** conflict. A lot of it's caused by things like short-term mating,
infidelity, and so forth. So, you know, as soon as the Kristen Stewarts, you know she
admitting to cheating on her boyfriend, Rob Pattinson, you know then I get a million calls
from the media wanting to know why, and what explains this, and why do people do things,
weird things, or what about Charlie Sheen? You know, why is he so gone off the rails?
Okay, speeding along here. I apologize. I've taken too long to get to some things.
Surgeon general's warning number three: they're evolved sex differences. I'm sorry. I should
be uncontroversial at this point, but there are. Okay, just as men and women differ on
average in height, in upper body strength, in body fat distribution, and things like
that, we also differ psychologically in certain domains.
Where do we differ? We differ in domains in which men and women have faced recurrently
different adaptive problems. We have a different reproductive biology. Fertilization occurs
internally within in women; not within men. That creates an adaptive [unclear] problem
for men: the problem of paternity uncertainty. Some cultures use the phrase "mama's baby,
papa's maybe" to capture that asymmetry. Females, but not males, have that obligatory nine month
investment to produce a single child; minimum investment for men is much less. So there
are these important aspects of our reproductive biology.
And to an evolutionary psychologist it would be absolutely astonishing and defy logic if
you have these fundamental differences in human reproductive biology, between males
and females, and you had an identical mating or *** psychology. And of course there's
a tremendous about of evidence that we don't. We differ psychologically where we face different
adaptive problems. We are similar, males and females psychologically, where we've, in essence,
faced similar or the same adaptive problems.
So another one is the issue of falsifiability. That comes up a lot. Well, you know, there
wouldn't be 8,000 studies in evolutionary psychology that have been published in peer
refereed journals that are well respected if the hypotheses weren't falsifiable. Well,
they are, and so I think it's helpful to talk about some that are and some that aren't.
So there are a bunch that have been confirmed by empirical data, or at least have fairly
sizable bodies of empirical data that support them, and there are some that have been falsified.
So the kin altruism theory of homosexuality, for example, the notion that males have an
evolved preference for virginity; one of my first studies falsified that hypotheses across
cultures. And the so called "loser male" design feature of the *** hypothesis; that also
has been falsified. It turns out that it's not just loser males who engage in ***. In
fact, there is some evidence that even males who are in a position of power or males who
are in a position to get away with it are more likely to ***. So there are hypothesis
or design features of hypothesis that, in fact, have been falsified.
I think it's important to show a sense of humor. You know, after all, we're dealing
with serious topics, so it's important to lighten up. So, I sometimes show my students
a cartoonist's rendition of the male brain. Okay, which is perhaps to derogatory toward
the male brain, including especially the listening particle, which some women seem to resonate
with.
This is the female brain. I think this is really wrong, and you know we can say well
what is the actual empirical data, but nonetheless, it's sometimes useful to lighten up a little
bit.
Another tool is to explain the heuristic value; that is evolutionary psychology guides us
to important domains of inquiry. And that's a hallmark of an important scientific meta-theory.
It guides us. It tells us things around mating and kinship are going to be very, very important.
It's consilient. Okay, to use E. L. Wilson's phrase, that is it organizes facts parsimoniously,
provides important guidance to new domains, leads to new predictions, and unites the field
of psychology with all the other life silences.
It's important to be humble and honest. We don't know a lot about psychology, much less
evolved psychological mechanisms, all their features. We discover more each year, each
month, but it's important to be upfront about what we know and what we don't know.
And the last point that I want to make is, it is an extreme privilege to work in this
time. Now can you imagine being a psychologist in the era of, I don't know, behaviorism,
or phrenology, or something like that? It is an exciting time to be working in the field
at this time, in the midst of what I believe is the most important scientific revolution
in the field of psychology that we have experienced.
So, if you're interested in these teaching tools, I have them all available on my website,
davidbuss.com, and I apologize for going a little bit over, but thank you for your attention.