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Thank you very much!

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I'm Joan Roughgarden
and I'm a biologist,

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and I'm here to talk about the evolution
of gender and sexuality.

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And, the reason I'm doing this is 
that I attended my first Gay Pride Parade

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in San Francisco 
about 12 years ago,

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and when I was there I noticed
this huge number of people

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all of whom, biology said 
were somehow defective.

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I thought that maybe it's not the people 
that are defective,

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but is biology that's defective.

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And, that began an investigation

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into the extent of variation 
in gender and sexuality

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which appeared in Evolution's Rainbow
the first of the two books

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that are on the screen here.

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Now, the issue 
from a biologist point of view

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with the diversity
in gender and sexuality

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is that it leads to challenges in what 
we teach in our ordinary curriculum.

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And, this is a very unpleasant
development,

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so the existence of gender 
and sexuality variation is problematic

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for biology and as you know,

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it's also problematic
in the political sector

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and the religious sector as well.

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Now, for biology specifically,

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the problem concerns 
an area of evolution

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called Darwin's Sexual Selection Theory.

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And I'll tell you what that's about

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and then show you 
that it's pretty obviously incorrect.

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The first proposition
that Darwin utters is that


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"Males of almost all animals
have stronger passions than females"

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so, we have the phrase 'passionate male' 
tracing back to Darwin.

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And, furthermore,
he says that the female,

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with the rarest of exceptions,

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is less eager than the male, 
she is coy.

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So we have the phrase 'coy female'.

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And, in today's jargon 'passionate male' 
is replaced with 'promiscuous male'

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and 'coy female' 
with 'constrained female'.

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And the third premise from Darwin 
is the most problematic.

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It pertains to characters 


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like the peacock's tail 
and the antler on a deer,

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and it is that females...

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And so Darwin was asking

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why does the peacock have the tail 
and does the deer have the antler?

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And his answer 
is that females choose mates

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who are more attractive, 
vigorous and well-armed,

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just as men can give beauty 
to his male [unclear].

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So, he's invisioning that females
are breeding males

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to have the traits that they have.

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Now, why, you might ask, 


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would females be chosing
males with ornaments?

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The idea is that the females 
have expensive eggs.

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And the males, on the other hand, 
have cheap sperm

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and so males are capable
in principle of ranging far and wide

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inseminating anything 
they come accross.

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And females are necessarily obligated

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to defend 
their expensive investment in eggs.

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Therefore, the female is forced 
to be coy and choosy,

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and the male 
passionate or promiscuous.

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And this is the party line

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that's currently taught 
in biology curricula worldwide.

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It's a nice story,
in a sense, at least it's a story.

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But the question is whether it's true.

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And let me show you some examples
of diversity in gender and sexuality

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that make these propositions 
almost useless.

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And one thing I need to emphasize
is that the two intial premises

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the passionate male 
and the coy female,

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are asserted as empirical generalizations.

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So, if you go outside and you pick up 
a random bird or a random butterfly,

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or any organism at random,

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the male is supposed to be passionate 
and the female coy,

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with very, very rare exceptions.

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And it will be obvious that the exceptions
are far from rare.

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The first issue is that the assignement

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into a sex, as male or female, 
is neither stable nor exclusive.

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If you go diving on a coral reef,

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about a third of the species 
that you see there

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consist of individuals
who are both sexes at the same time.

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Or at different times during their life.

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So, in the case of these species
right here,

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the individuals change from female
to male, that is a kind of wrasse.

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In the case of this species right here

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they change from a male to female.

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And as I say, 30% of the species,

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if you simply go snorkeling 
on a coral reef,

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you see this all around you.

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And it's just simply not true

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that the categories of males and females 
are stable or comprehensive.

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Now, another important issue is called 
'Sex-Role Reversal' by biologists.

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And this pertains to males 
who do all the parental care


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and females 
who have to hustle around

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and find a male 
who is interested in them.

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And the popular examples 
of this are the seahorses.

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Now, in fish, the parental care 
is usually provided by the male.

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And in birds, 
it's about 50/50 male and female

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and in mammals 
is usually initially by the female.

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But in fish, the style of parental care 
varies from species

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and in many cases the males 
will glue the eggs to their tummy.

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And that is true of... darn!

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That's true of this species
in the middle here which is a pipefish.

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Now, the seahorses 
are related to pipefish

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in that they have 
a big skin-flap on their tummy

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and the females deposit eggs 
into the males' tummy.

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So the males become, 
in a sense, pregnant.

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So, this is a male seahorse 
receiving eggs from that female.

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And what happens in this situation

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is that you can get more females 
hanging around

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looking for males to receive their eggs,

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and in that situation then 
the males are in the position to decide

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what female they want to allow 
to deposit eggs in their skin-flap.

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So this is the exactly the reverse 
of the Darwinian story

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that it's females
who are choosing males,

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here it's males
who are choosing females.

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Now, that shows that the size of the sperm
or the egg can't be important

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or definitive in determining 
the sex-role of the animal.

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Because male seahorses 
make tiny sperm

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but yet they are nonetheless the ones
who wind up doing all the parental care.

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In many species 
there are several genders of males.

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In this species called the ruff

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the one on the left 
is a male with a black collar around it

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the one at the top has a white collar,

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and the one on the far right
has no collar.

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Now, the black colored males,
at the time of mating,

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go into an area which is called a 'lek'

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which is basically 
a red light district of males.

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And, when the females 
are foraging by themselves

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and they want some sex,

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they just go and fly over to the lek

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where all the black colored males 
are hanging out

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and then the males try to attract them 
into mating with them.

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But the plot thickens,

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because this white colored male
at the top,

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hangs out with the females
for a little while and gets to know them,

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and then he leaves those females 
before they approach the lek

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and he goes to the lek
where the black colored males are,

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the black colored males court him
and ask him to join them.

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So, when the females arrive

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they find some territories
with two colors, two styles of males,

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and the females prefer to mate 
with the pair of males of the two colors

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rather than with the males 
with one color by itself.

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And, I conjecture that the reason
for that is that the white colored mates

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get to know the females

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and can serve, so to speak, 
as marriage brokers,

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when the females
fly into the black colored males

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they can make introductions 
and invite specific females to join them.

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In any case,

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the existence of multiple types of males 
also contradicts the Darwinian story

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in which all males are of one type 
and all females another.

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Then, we get to the question 
of homosexuality.

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There's a lot of mating that takes place
between animals of the same sex.

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And these are elephants right here.

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These are big horn sheep from Montana.

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And these are primates, 
our closest relatives.

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And there's well over 300 species
of vertebrates alone

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in which same sex sexuality 
has been observed in nature.

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So, this is quite common.

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And officially observed
and published in the primary literature.

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Now, these are gorillas on the left,
which is a male-male interaction

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and now in the center and right

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we have a female-female interaction 
between bonobos.

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And female bonobos, well,

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mate with one another several times 
during the day,

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as a form of networking.

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So, what's really going on here

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is that there's a lot of physical intimacy
between animals,

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not only same sex sexuality, 
but also multiple grooming,

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reciprocal grooming, 
reciprocal preening.

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And all of these forms of behavior 
are ways of exchanging physical pleasure

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with one another.

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And I've suggested that the reason

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this evolves is as a mechanism 
to produce bounding

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and collaboration between individuals.

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And when individuals
are physically intimate with one another

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they're able to coordinate
their activities

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and work toward a common goal

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because they experience mutual pleasure 
in achieving a common goal.

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So, it's actually the realization 
of the common goal

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that is pleasurable 
in these intimate interactions.

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Now, in light of all of this

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the whole idea of sexual selection 
looks almost absurd.

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It's incorrect, but it also is irrelevant,

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it doesn't even address the degree 
of diversity that occurs in nature.

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The issue of collaboration 
brings us to the next issue

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which is the one of family.

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And biologists, I believe, also 
have an incorrect account of family life.

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This is a quotation 
from Jeff Parker in the U.K.

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"The family is now perceived 
as a cauldron of conflict,

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with each of the players 
having different interests...

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sexual conflict, 
parent-offspring conflict,

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and sib-conflict simultaneously."

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And this too is taught 
in the biology curricula.

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And, if it were true, it paints 
a bleak picture of the aspirations

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that we all share here 
of building a better life

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and founded on collaboration, 
but it may not be true.

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The idea of biological family

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that I've been suggesting
in the last year,

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is summarized in this diagram,

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in which the parent-parent relatioship 
is essentially colaborative

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and the collaboration is realized 
through physical intimacy

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that produces cooperation 
that resolves genetic conflict.

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Because we can't avoid the fact

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that there is genetic conflict 
at the beginning.

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But it needs to get resolved.

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Now, with respect
to the parent-offspring relationship,

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my suggestion is that there is an effect 
in auction of resources to offspring

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that produce an incentive 
to resolve the genetic conflict.

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And what I'm doing here 
is drawing on the economic theory

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of the firm from economics.

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And viewing a family as it was a firm
or a company whose products is offsprings.

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And asking whether 
or not the organization,

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the economic organization of a firm,

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could serve as a guide 
to understanding animal family life.

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And the specifics are 
that in the parent-offspring firm,

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the parent is in the position 
to give food to the offspring,

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and what the parent does is indicates 
the price of the food to the offspring

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and the offspring pay for this
by the quantity

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of begging that they carry out.

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And the offspring are able to communicate 
their demand curve to the parent.

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And if the parent knows 
the demand curve

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it can set the price of food 
that it charges to the offspring,

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so that the offspring honestly communicate
their needs to the parent.

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And when that happens the family functions
as a very efficient unit

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for the production of offspring.

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And therefore we get the formation 
of collaboration in two ways.

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Either through collaboration, 
either through physically intimacy

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which produces a collaboration.

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Or through the setting of incentives, 
and the circumstances differ.

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So, I've been blessed in all my work 
by the help of these collaborators,

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Erol Akçay, who's from Turkey, 
and Priya Iyer, who's from India.

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So, thank you so much.

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(Applause)