By Jessica Hamzelou.
The bottlenose dolphin is asexual.
Alamy Stock Photo has an imageBROKER.
The evolution of animal genitalia has been studied by a controversial woman. She believes that bottlenose dolphins have clitorises that have evolved for pleasure because of the amount of sex the animals have. Brennan tells New Scientist why it is important to study female genitalia.
Why study dolphin clitorises?
A researcher was studying vaginas in dolphins. Dolphins have vaginas that are very complex. The hypothesis was that the folds were there to exclude salt water from copulation. Nobody had ever tried to test the idea of these folds.
We don't know why they are that way. I would look at the clitorises when we did the vaginas. I was like, "Oh my gosh, these are big, well-developed clitorises." I thought it might be interesting to look at.
Female dolphins have weaponised their vaginas.
We know that dolphins have sex. They have sex for social reasons. It makes sense that the clitoris would function.
Is dolphins having sex all the time? Is they more sexually active than other animals?
We don't know if they have more sex than other mammals. It is difficult to study sexual behavior in cetaceans because they are out there. Scientists can go out on their boats and study bottlenose dolphins, which live close to the shore. They see them having sex year-round, even when the females are not receptive, so not ready to get pregnant and have babies.
They have a lot of homosexual sex as well. The females will rub each other's clitorises with their snouts and flippers. It is not uncommon to see females stimulating each other in a blue moon. Females masturbate.
It is likely that they are out there looking for all these sexual experiences.
Do you see the same things in males?
The males have a lot of homosexual sex. The males will have sex with each other. Hypersexual dolphins are bottlenose dolphins.
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How did you study dolphin clitorises?
They came from dolphins that have died from natural causes. It has taken years to get a sample size that is good enough for a study because it is rare that an animal becomes stranded and that a scientist finds it before it has decayed too much.
We get a package that was sent overnight. They come from all over the US. When they arrive in our lab, we begin to thaw the tissues and perform the dissections.
We cut around the clitoris structure as much as we can, and then do a couple of different things. We stain the tissue so that we can see the soft tissue in a microCT scanner. Some samples are analysed under a microscope.
What are you looking for?
We were interested in looking at the tissue of the penis. Is there any places within it that could hold blood? Does it have a blood supply that shows blood rushing into these spaces? This is what happens to people.
The tunica albuginea is a thick band of elastin and collagen that surrounds the penile tissue. The presence of this tissue suggests that it prevents the tissue from bulging out.
The nerves are looked at as well. They have large nerves. Some of the nerves are up to half a millimetre in diameter. We were shocked by how big they were, there weren't many measurements that we could compare them to.
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We were able to see the free nerve endings underneath the skin. These increase sensitivity. We have these in abundance in our hands and in the clitoris and glans penis.
The skin in the clitoris is about three-quarters of the thickness of the skin in the genitals. We were pretty sure that this is functioning in pleasure, just like in humans, once we put all of those things together.
Does this tell us anything new about dolphins?
No. It makes perfect sense to me. Dolphins and females have a lot of sex. The clitoris of theirs is very well developed and it looks like it provides pleasure. It makes sense. It shows the evidence we need to close the case and say, yes, this is what a clitoris looks like.
Is this controversial?
The clitorises are just a mini penis because they share the same developmental pathway. It doesn't have a function and isn't designed for anything. Males have a penis.
There is a debate about whether orgasms are functional. It is one of those things that will not die.
The sexism in sex medicine is revealed in female orgasm debates.
As a female scientist who studies sex and sexual reproduction, I have a problem with the idea that there would be no function for a structure if it was not related to the penis.
This is a fully functional organ that is serving some kind of purpose, and we can show that this is more than a mini penis. It makes you want to have sex more often.
Where is the research going?
We can start looking at other species that you wouldn't keep in a lab and ask the same questions now that we have this set of criteria. bonobos have sex all the time, and their clitoris looks like a human one. It is easier for people to imagine that a bonobo is having sex and making a loud noise, like we do.
Dolphins are very different from other animals. We are starting to look at the same types of features in the alpaca clitoris. We have a lot of animals. In my lab, we work with a variety of animals. We always find something interesting.
What about male genitalia?
We collected a lot of penises and are interested in how they function.
I study genital coevolution. I want to look at how males and females co-evolved. When it comes to genitalia, you have to look at both sides of the equation to figure out how they work.
The job of genitalia is to facilitate male and female gametes getting together, and you could have a tube going into a cylinder that would achieve that basic goal. But genitalia are not like that. They have a lot of weird features. They have pockets and spirals. We are trying to understand the evolutionary processes that affect their function.
The battle of the sexes is fought in the genitals of ducks.
We study both of them, but we don't know a lot about the female because people tend to study the male more than the female. We are catching up with the female stuff.
Critics questioned the importance of your research in the past. What do you think about people who say this kind of work isn't relevant?
It's basic science. It isn't designed to solve a problem. When people ask why we study it, they want to know if it will make money or cure a disease. Maybe, we don't know. We are trying to understand how natural phenomena work.
Your question is about something else. Some people are not comfortable with studies of sexual behavior in humans or animals. Sex isn't unimportant or that we shouldn't be studying it.
I could be looking at the stomach, and that wouldn't bother people. Sex and sexual reproduction is one of the reasons people are bothered. That is understandable, but I am a scientist. I ask questions where I think there are interesting questions to be asked.
The interview has been edited to make it clearer.
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evolution
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