"...will we do away with whole areas of
the earth, then face what it's like to have ten to twelve billion people
on this planet?"
with Robert Trivers
Are social behaviors genetically inheritable? Do they evolve through
time like physical characteristics? The science of sociobiology has
developed in order to study these questions. In the controversial field of
sociobiology, there is no one as controversial as Robert Trivers, for he
has certainly been the most daring in applying the "selfish gene" theory
of sociobiology to human behavior and psychology. Recognized as one of the
world's most eminent sociobiologists, Robert Trivers was born in 1943 in
Washington D.C. to a Foreign Service Officer and a poet, as the second of
seven children. His early academic interests ("after the Bible, " he
clarifies) included astronomy and mathematics. He earned his B.A. from
Harvard in U.S. History in 1965. Then he wrote and illustrated children 's
books for two years before returning to Harvard, where he studied biology,
and received his Ph.D. in 1972. He taught at Harvard until 1978, and after
that at the UC Santa Cruz, where he continues to teach to this day. In May
1979 he joined the Black Panther Party, and has been referred to by his
colleague Burney Le Boeufas "the blackest white man I know. "
Dr. Trivers is perhaps most famous for his theory of reciprocal
altruism, which is a model for explaining and predicting altruism in
animals precisely based on return-effect or chances of reciprocity. He has
also written papers on parental investment and sexual selection, sex ratio
theory, parent-offspring conflict and the social behavior of lizards and
insects. He is the author of Social Evolution, a fascinating
sociobiological textbook which was published in 1985 by Benjamin-Cummings
of Menlo Park. He spends a good deal of time in Jamaica with his children,
and has described himself as "Jamaican in my soul or spirit. " He is
currently working on the evolution of "selfish genes " and resulting
intra-genomic conflict, the effects of blood parasites on sexual selection
in Anolis lizards, and deceit and self-deception. We met Bob on the
evening of January 18th, 1 989 at the Woodshed, a country bar in Felton,
California. Bob spoke to us about his theory reciprocal altruism, selfish
genes, the evolution of sex, and muses with us on how and why
consciousness evolved. There is a wild unpredictable quality to Bob's
personality. He seems untamed and street-wise in a rather charming sort of
DJB: Bob, what was it that originally spawned your interest in
biology and the evolution of social behavior?
ROBERT: When I graduated from college I was offered a job
writing, and later illustrating children's books for part of a curriculum.
The curriculum was called "Man: A Course of Study," and was meant to be
the new social science, analogous to the new math, and the new physics.
Since I didn't know anything about humans, they asked me to work on some
animal material that they wanted to include in the course. I also didn't
know anything about animals but they cared less about getting that stuff
So my first exposure to animal behavior came through this job, and I
was impressed with two things. One, by watching movies of baboons, I was
impressed by how psychologically similar they seemed to ourselves, and
that any explanation therefore of our own psyche would have to include
arguments that could apply to baboons as well. And the second thing was I
learned about the concept of evolution through natural selection. So
within about six months of graduating from college, I had had my life
turned around. I had never had biology before, never had chemistry, and I
became convinced that the basis for a scientific theory of psychology lay
in animal behavior and evolutionary theory. So I threw myself into it.
DJB: Can you briefly describe your theory of reciprocal
ROBERT: Reciprocal altruism is very, very simple and encompassed
in the folk saying, "You scratch my back, I'11 scratch yours." It simply
posits that organisms, besides humans, or in addition to humans, are
capable of trading altruistic acts over a period of time, in which each
individual is sensitive to the tendency of the other individual to be
reciprocal, or perhaps not to be reciprocal, or as I put it, to cheat on
the relationship. So the theory of reciprocal altruism applied to humans
says that traits like friendship did not evolve before reciprocal altruism
as a prerequisite, but evolved after reciprocal altruism as a way of
motivating and shaping our reciprocal relationships.
RMN: According to the theory of natural selection, species
evolve to adapt to the local environment to align with the forces of the
external world. For example, the Spots on the heads of gull chicks will
co-evolve with the parental ability to recognize them. Have you considered
the possibility that this process may operate both ways; i.e., that the
environment may also adapt to conform with the needs of the organism it is
nurturing and does natural selection support the idea of evolution as a
co-creative transaction between the organism and the environment?
ROBERT: I have considerable difficulty with that notion, except
in the sense that you probably don't mean it: that the environment
consists of other living creatures, and so the environment and the species
we're considering both evolve. The species we're thinking about imagining
is selected by the environment it lives in, but the environment it lives
in is itself made up of living organisms which are being selected by
reference to their environments, which include the species we're
imagining. But, if you ask can I see how the environment would evolve to
nurture the species, I'm dubious.
DJB: What percentage of human behavior do you think is
genetically hard-wired and what percentage of human behavior do you think
is due to environmental learning, and what evidence can you call upon to
support your viewpoint?
ROBERT: I don't think your question really permits any kind of
precise answer. I think it's inherently impossible to assign a percentage
to environment and a percentage to genetic influences. The only way you
could do that would be to specify the full range of environmental
contingencies, and the full range of genetic contingencies, and that seems
like a hopeless way to operate. For example, traits like two legs and five
toes on each leg are "hard-wired" genetically, but we can always produce
an intervention in early embryology which will interrupt the natural train
of events, and result in someone with no limbs, or with an unusual number
of digits. So, if we include that environmental range, then the percentage
of genetic determination drops below a hundred percent. I don't see any
way to state how much of human behavior is genetically hard-wired,
whatever that precisely means, or how much is environmentally determined.
DJB: Bob, you wrote the introduction to Richard Dawkins' book
The Selfish Gene, the first place I ever heard of the concept
of memes-that is, non-genetic clusters of information that replicate
themselves from brain to brain much as genes do from body to body, and
appear to evolve through a process akin to natural selection. In light of
this theory, can you explain why some people forfeit opportunities for
genetic reproduction in order to propagate memes-many artists and
scientists, for example, never have children--and do you think it's
possible that the goal of evolution is not really genetic replication, but
rather information replication?
ROBERT: Once again, I just have to express myself as being
dubious. I was dubious of the attention that Dawkins gave to the concept
of memes in his original book, and I don't see ideas replicating
themselves between people, and being selected in a process analogous to
natural selection. I see each of us trying to influence others via our
ideas, and each of us being selective regarding the ideas we accept and
the ideas we reject, and the way in which we decide to modify ideas that
we do accept.
A general term like information transfer, or information maximization,
might work better. I just don't know how to relate to it within the one
system of thought that I'm comfortable with, which is evolutionary theory.
Regarding the notion that many artists and scientists have few or no
children, I don't know what the evidence for that is. If it were true, I
suppose I would fall back on some hunter-gatherer imaginary scene in which
the shaman or the artist made a disproportionate contribution to the
welfare of his or her local group, and this made up for any deficiency in
RMN: You say that natural selection is described as disruptive
when it favors extremes to create a polarity and you cite human sexual
dimorphism as an example. What do you mean by this?
ROBERT: Well, you'd have to go a ways back in our own lineage,
but if you go back in any species that has two sexes, you'd reach a
species where there's only one sex, an original hermaphroditic form, which
gave rise to the species with two sexes. Now, once you have two separate
sexes, if selection operates against intermediates, then it'll tend to
push the two sexes further apart.
So to use a crude compelling example, men with breasts or women with
masculine characteristics may be less well off than firmly belonging to
one sex or another. So to that degree selection operates against the
intermediates, and we have to imagine, whenever we see dimorphism in
nature--and sexual dimorphism is just one example--that somewhere along
the line selection was disrupted, acting against the middle, and in favor
of two different positions, not extremes, but two different forms or
RMN: So, by disrupted you mean it's moving away from the middle?
ROBERT: Yeah, I think so. The only other image of disrupted that
I can think of is that if you have a normal distribution to begin with-- a
single uniform distribution-- and you disrupt it, you'll end up producing
two distributions instead of one.
RMN: The term "disruptive" sounds a little pejorative.
ROBERT: Well, if you'll pardon me, I wouldn't attach too much
significance to the term disruptive as in disruptive selection. I see your
objection and did when you were asking your earlier question, but it's
just a term like normalizing selection and directional selection, just for
describing a kind of selection. Now, getting back to the union of
opposites--sure, in some cases, as in the sexes in producing offspring.
But, I guess answering your question I realize that I came out of a world
twenty years ago in which differences between the sexes or within species
tended to be minimized and conflict tended to be minimized, and there was
always some claim of a higher purpose, benefits for the group or the
species, and insufficient attention was paid to conflict, even within
relationships that have a cooperative goal. So regarding the sexes, yes,
especially in species with male parental investment, especially in cases
of monogamy, you can have a large overlap of self-interest between a male
and a female, so they're involved in a higher goal, a common goal of, let
us say raising offspring together.
RMN: Which is what life is all about, right?
ROBERT: Eventually. But that still should not obscure the fact
that they have conflicting self-interest, and that their self-interest may
not be maximized in the same way.
DJB: James Lovelock and Lynn Margulis have proposed a theory, which
they have termed the Gaia hypothesis, to explain how and why life forms on
our planet work in such a cooperative fashion together to achieve the
delicate chemical ratios in our oceans and atmospheres, which are
maintained in such perfect balance that life is made possible and
sustained. They claim that the whole earth seems to function much in the
way a single organism operates. Do you have any thoughts on this, and how
does the "selfish gene" theory that you subscribe to explain this
extraordinary phenomenon? ROBERT: Well, I'm really not familiar
with this area. From my bias, I've always imagined, in so far as I've
thought about it at all, that the organisms are just busy concerning
themselves with what's good for each other, and the result is some kind of
steady state that is beneficial, more broadly put. Some organisms consume
oxygen, others generate oxygen. There's going to be a balance struck
between those two sets of organisms, some kind of density-dependent laws
that come into effect.
I think that it would be a mistake to imagine that the organisms are
attempting to set up something in the biosphere itself, or to create a
biosphere, but I may be a little bit old-fashioned in that approach, and I
know that geologists, and people that study the earth as a whole, do often
imagine that it's like an organism, and maybe it is. I just don't know.
Nothing in my line of work would suggest so, that I know of.
RMN: You refer a number of times in your book
Social Evolution to the "apparent coincidences" of natural
selection. When literally translated this term coincidence means simply
the coordination of incidents. Would you venture further and postulate as
to the directing force that is coordinating these incidents? Do you see
any kind of teleology in nature or
do you view all events as the product of mere chance? Does Natural
Selection play dice with the universe, and is the only meaning to life in
your view, really, more life?
ROBERT: I don't see any teleology in nature. The teleology was
beaten out of me in my training. It was an important aspect of
paleontology, for example, to learn there were no trends, inevitable
trends, of groups tending to always get larger, or always go in one
direction or another.
RMN: What are your views on genetic engineering and the
possibility, which to some scientists is a very real one, that we will
soon have the ability to control our evolution by programming our future
ROBERT: I have not been frightened by genetic engineering. I do
not believe it will create monsters that will run rampant. I've always
believed that natural selection would still be acting, and acting very
RMN: On the scientists that create the genetic mutations?
ROBERT: Well, I was thinking on the genetic mutants themselves.
In other words, when the, say, anti-frost bacteria were first sprayed on
plants here in California experimentally, people said, well Jesus what
happens if you got a monster bacterium that's going to cut loose and cause
all sorts of havoc, and run amok. I just didn't imagine that it would
happen because monsters are being produced, probably daily, in this world,
through mutation and recombination, and are being selected against, and I
didn't see, and don't see any reason why artificial forms created in the
lab wouldn't be subject to strong selection too. As for genetic
engineering in the human species, I imagine it's inevitable, and Probably
in a hundred or two hundred years we'll scarcely be able to imagine the
genetic manipulations that'll be possible.
RMN: In your book Social Evolution you state that the
primary function of sex is to generate genetic novelty in the offspring,
which can better adapt to the changing environmental conditions. You also
say that natural selection favors individuals who maximize the number of
offspring. Two factors are being described here--that of quality and that
of quantity. How do you see these factors operating in evolution?
ROBERT: The simple answer is that quality can always be
converted into quantity for the purposes of evolutionary theory. So, one
pair of parents can produce four offspring of low quality, where quality
is measured as their ability to survive and reproduce, and another pair of
parents can produce two offspring of high quality, were quality is again
defined the same way. In that case, after awhile, the high quality
offspring win out, are more numerous. That's just a tautological system,
in which quality refers to eventual ability to survive and reproduce, and
therefore converts into quantity.
RMN: Do you see these influences as being equally potent--
DJB: Approximately 22,000 Americans commit suicide annually.
Clearly suicidal behavior is non-adaptive, and it appears to he related to
sexual development- that is, the behavior seems to emerge during
adolescence, and is often triggered by the loss of a lover. How do you
explain it evolutionarily?
ROBERT: I don't necessarily explain it evolutionarily.
Twenty-two thousand out of two hundred million is still a relatively low
frequency. Evolutionary arguments have to start being evoked where you get
up to one percent of the population, or something like that, as in
schizophrenia. Your statement that suicide is clearly non-adaptive, I
think, has to be viewed with a little bit of suspicion. I'm not saying
that it is adaptive, but I'm saying one can imagine circumstances under
which suicide is adaptive.
You can start with the old Eskimo story of the elders who walked out
into the cold to die, to save their children energy and effort. A certain
amount of suicide of the elderly has that form. It is also possible for
suicide to be adaptive when the alternative is murder of close relatives,
or some other behavior that's going to bring genetic consequences. I think
there might be a recent paper, that I've not read, on an adaptive approach
to suicide, but I don't see any obvious adaptive sense to it.
RMN: Neophobia, the fear of novel stimuli, can be viewed in some
situations as enhancing reproductive success, and in other situations as
inhibiting it. If one species evolves to be fearful of novelty, and one
species evolves to embrace novelty, how do you think those two species
ROBERT: I think put in that extreme form one would tend to place
one's bet with the species that embraced novelty, just because novelty is
intrinsic to the living world. Evolutionary novelty is occurring in all
species, and other species are part of our environment. So even leaving
aside geological and climatic changes, which are themselves occurring,
there's novelty always being generated. So it's hard to imagine a
long-term strategy successfully based on extreme neophobia. On the other
hand, a lot of creatures, speaking strictly off the top of my head, seem
to show some sort of balance between extreme neophobia and just rampant
embrace of everything new. I could think of different species, different
examples, where the young are, like I say, somewhere in between.
DJB: Do you believe that life may have evolved on other planets
and star systems, and if so, what possible courses of evolution do you
think they might have taken that would be different from our own?
ROBERT: I do believe that life has almost certainly evolved
elsewhere. Our best understanding of astronomy and of the origin of life
on this planet suggests that there are plenty of stars that are
appropriate, plenty of planets presumed around those stars that are
DJB: Several years ago, Nobel prize winner
Francis Crick, the
co-discoverer of the structure of the DNA molecule, wrote a book entitled
Life Itself, in which he proposes the idea that life may have
been seeded on our planet by a species of higher intelligence than our
own, through the use of genetically engineered spores that are blown
through space by radiation pressures. In the light of our own species'
progress with genetic engineering, do you think this is a possible
explanation for how life originated on our planet, and if so, do you think
it is possible that evolution may, in some sense, be developing according
to a particular plan?
ROBERT: I think it's possible. I don't quite see the gain to the
other organism in doing this process. The seeding of the earth, according
to our understanding, would have then occurred about four billion years
ago, and it took four billion years to produce creatures as humble as
ourselves. We can't do yet what Crick is saying the other creature can do.
So after four billion years they still ain't got nothing that matches
themselves. I don't quite know what the function of this would be.
RMN: There is much concern these days about the problems of
over-population. It seems that the survival of the human species, and
possibly the planet, may now depend upon our ability to limit
reproduction. As natural selection theory depends upon the idea of
reproductive success being the main goal of evolution, what are your views
ROBERT: I think that, next to nuclear warfare, it's probably the
best candidate for driving us to extinction, perhaps in conjunction with
nuclear warfare, of any of the possible candidates. I think a lot will
depend on how far we deplete resources before we reverse the population
explosion, assuming we finally reach a stage where we do. Certainly at
some point we have to limit reproduction to a ZPG, zero population growth,
or steady-state. We know that from elementary considerations.
When I think about the future in that regard, which I do very rarely, I
imagine the next hundred years will be crucial in determining what we have
to bring ourselves back from. In other words, do we all go the road of
India before realizing that there are unfortunate consequences of
depleting your natural resources. In India you can go to these beautiful
geological strata, four thousand feet up, the mountains and hills near
Bombay for example. You see the complete deforestation of these areas,
which leads to the alternate cycle of floods, where hundreds and thousands
die in floods, and then tremendous periods of drought.
I remember coming back down from this place, going towards Bombay, and
there are these Mangrove-like trees that send out roots from their lowest
limbs, and goats were reaching up on their hind legs, and nibbling the
growing tips of these roots, that far from the ground, and they weren't
going to reach the ground, because there was always going to be enough
goats to keep them from reaching the ground. So the trees weren't going to
grow anymore, and it just seemed like ecological chaos. So anyway, when I
think about the future at all, I imagine will we do away with the
Brazilian forest? Will we do away with whole areas of the earth, and then
face what it's like to have ten to twelve billion people on this planet?
Or will things get under control before then?
DJB: Bob, do you think it's possible that the introduction of
psyche-active plants into the food chain of early primates had any
influence on our evolutionary development? Terence McKenna thinks that
psilocybin mushrooms catalyzed the enlargement of the neocortex and the
development of language. Roland Fisher has shown that low doses of
psilocybin increase visual acuity.
ROBERT: I don't imagine it's had any, or much of an evolutionary
RMN: Do you have a theory about why the brain size of Home sapiens
increased so rapidly over such a short period of time?
ROBERT: I don't have any particular theory, no. It seems to me obvious
that it must have been bound up primarily with language. Which is another
great unique development in our own lineage. We know now of animal
languages, and in primates we know that various species do use some sounds
symbolically. But these are very, very rudimentary compared to our
language. So, I think it must have gone hand in hand with language. I
think reciprocal altruism was bound up in it, because I don't think you
get selection for much language, unless you have a back and forth kind of
relationship, where each benefits from the interaction. Even then I think
of language initially as starting in families, and spreading among close
relatives, and being beneficial that way.
RMN: What possibilities do you see for our future evolution, of humans
or other species?
ROBERT: I haven't thought much about future evolution. Again, it's
contingent in our own species' case with getting the population growth
under control, and what form that's going to take- whether it's natural
disasters and non-nuclear war, and that kind of thing, that's going to
keep populations under control, or whether it's some kind of voluntary
restraint, it's hard to guess. It's hard for me to visualize what system
of reproductive competition will exist in the species, after we get the
population growth under control.
DJB: How do you think consciousness evolved, and how do you see it
evolving into the next century?
ROBERT: Well, I'm not sure what consciousness is. I think insects are
conscious to a limited degree. I don't think they're highly conscious or
acutely self conscious, but I think there's a little light turned on in
insects that I've played with, and they're conscious of what's going on.
How do you see it evolving in the future, Dave?
DJB: Well, I see brain capacity, and information processing abilities
increasing, for one thing.
ROBERT: Increasing? So, that assumes now that bigger-brained people are
leaving more surviving offspring?
DJB: Well, what I'm looking at is the overall 4.5 billion years of
evolution, and brain capacity has increased, intelligence has increased.
ROBERT: Yeah. Right.
DJB: So, I see the pattern continuing on into the future.
ROBERT: But do you disagree with my statement? In other words, you see
bigger-brained people leaving more surviving offspring.
DJB: Well, actually, I think I see exactly the opposite. I don't know
about the size of people's brains, but I see those who are less educated
reproducing more quickly than the more educated, unfortunately. I wonder
why this is?
ROBERT: Well, you see this is the conflict between a teleological or
orthogenetic view of evolution, and one that always insists that natural
selection be behind it. You can't extrapolate from past patterns, unless
you imagine there is some momentum, or force, carrying you through to the
future. If you believe in evolution through natural selection, then you
believe in the changes, which have been general, but not universal towards
greater brain size. If you look at the vertebrates, there's been increase
in brain size, in mammals over the last 150 million years, Been no
increase in fish in 400 million years. No increase in amphibians, so far
as I know. Increase in birds. Even in human lineage, I think there's no
evidence of any increase in the last 100 thousand years. I'm not so sure
about that statement. I know Cro-Magnon man was sort of a large-bodied
form, but it had...
DJB: A larger cranium.
RMN: I heard that at some point they had brain capacities larger than
we have now.
ROBERT: I've heard that too.
DJB: Why do you think consciousness evolved in the first place? How is
it even adaptive?
ROBERT: Well, again, it depends on what we mean by consciousness.
DJB: Awareness, the opposite of being unconscious.
RMN: Or the ability to receive and transmit information.
ROBERT: Yeah, to me, it's just some kind of a heightened mental
faculty, allowing heightened learning, and quicker responses to on-going
events, which, however, is costly. I always use the analogy of an electric
light being switched on, or not being switched on, partly because we're so
visual, and our images of consciousness are so visual. And a light bulb is
expensive, so we sleep, or we have periods of unconsciousness to rest what
is a very expensive kind of ability.
DJB: Can you explain your theory of self-deception?
ROBERT: I tend to imagine that in social species, especially where
there's been selection for deception, and spotting deception, then there's
been selection for self-deception. This is a new kind of unconsciousness,
where you systematically hide the truth from yourself. I tend to think
that self-deception has been as important in human history as mental
acuity itself is.
I'd rather have a leader that was minimally self-deceived, and not
quite as quick with his brain, than someone who was quicker, but practiced
a lot of self-deception. So when you talk about the future of
consciousness, my mind goes around, and I think about self-deception, and
how selection is operating with regard to that, and it's just so hard to
speculate when we're talking about things on a time-scale of a few
thousand years, at the least, to get some natural selection going that's
going to show up with something.
While at the same time, we know that in the next couple of hundred
years we're going to see radical changes, I think, in our environment,
including our medical environment, including this bio-engineering
business. Because bioengineering starts to get into conflict with natural
selection if we start talking about changing our genome, the genome that's
in our gonads. A small amount initially would create only a small effect,
so we're going to go in, and we're going to get rid of my bad eye genes,
and a few other bad genes. That's very minimal.
More extensive revision of yourself is like almost interfering with
personal genetic reproduction, and I think those forces are going to be
large and looming before regular old natural selection has had time to
produce a human that's much different than ourselves. An issue that I cut
myself off from has to do with social cost. Normalizing selection chops
off the extremes all the time, and keeps the species close together.
Right now there's three percent mortality in our society between age
zero and age twenty-five. That's very very small. Next to no variance can
be generated by that small a selection. So then let's assume ninety-five
percent of individuals couple up, or marry, and it isn't too far off from
that right now. And let's assume everyone has two children, and let's
assume you're supposed to have two, and you're not supposed to have any
more than two, and if you lose one, you replace it.
Well, an intriguing argument that was published a few years back said
after awhile the species will start coming apart, because you'll no longer
have normalizing selection. So, in the extreme case, after fifty
generations of this or something, your baby will require a certain kind of
pills to keep it from having trembling spasms, and my baby will require
that it keep it's left leg in warm water for a half an hour at night, and
all of us will grow up with these environmental demands that are necessary
to compliment what normally would just have been taken care of
So the social costs begin to go up, but right now we already have so
many social costs from related biological things that don't have to do
with natural selection. I'm thinking of matters like the elder generation
and the result of medical advances. Now we have people who can live
miserably between eighty and ninety, just dreadfully. I don't know if you
all have been into any of these nursing homes. My wife worked in them and
I used to pick her up. I couldn't take it. I'd wait outside. There were
people screaming all night long. You know, they've been in there for six
years screaming, and they'll be in there for five more screaming, and
that's it. They're looking forward to death, because the screaming is all
So, there is a case where suicide, I think, can be adaptive in several
senses of the word. It certainly makes some sense if there was a
dignified, good way to do it. I'd just say well, Dave is eighty-three now,
and he's not taking care of himself, and he's going to have this farewell
party, and we're going to say good-bye.
RMN: It'll be a happy occasion.
ROBERT: Yeah, something like that--a happy occasion. His relatives and
friends gathered around.