I envy the scientists of the nineteenth century. Regions remained unexplored, basic principles remained undiscovered. Science was a two-fisted, swashbuckling enterprise where the white heat of discovery was vital and immediate. Hundreds packed in to see Huxley and Wilberforce debate evolution, millions more read about it. The fate of humanity’s view of itself was held in the balance by such discoveries.

All of that is, sadly, a thing of the past. No more dazzling discoveries to unseat humanity’s arrogance. No more fabulous un-coverings of missing links, or equally fabulous frauds. No more fundamental principles to uncover, building blocks of life to unravel, or atoms to split. Some spectators on the side-lines have claimed that science is at an end—we already know everything that matters. Just some details to fill in. (1)

Just boring old science shuffling along in its carpet slippers, dull as stamp-collecting, cataloguing and documenting. Dusty and boring. The preserve of nerds and geeks. Sigh.

We poor scientists weep for there are no more worlds to conquer.

And then something like this happens!

Headline news
Actually, not the first

Evolutionary biology is really not for sissies (2). One minute you are patiently examining a new species of insect intromissal organ under a microscope, vaguely wondering where your next grant cheque is coming from. (3)  The next moment your discovery is so momentous that “scientists are stumped”, “evolutionists are baffled”, “creationism has been vindicated” and the whole endeavour of trying to understand humanity at all has had to be discarded. “Take that evolution” cry the creationists. “So much for evolutionary psychology”, crow the social constructionists.

Worse is threatened—your discovery is so unsettling that, according to one over-excited commentator it might “undermine the power science has to unveil real truths about the universe”. (4)


A penis by any other name would swell a gamete

Neotralga sex
Neotralga mating

What is this momentous discovery?

Ready for it?

Here it is…

Females can have penises.

Specifically it’s the finding that the females of four species of Neotralga possess penises to transfer gametes from the males has made some commentators all of a Twitter ™.

Time for a reality check. Some folk, full of righteous anger over societies’ often pernicious sex roles, think that the best way to combat these is to deny that there is any reality to sex differences. Let’s be clear: If there weren’t sex differences then females would not create males. They could just clone themselves, as bdelloid rotifers still do, 85 million years after abandoning sexual reproduction. (5)

Man and woman made he them?

Zac Weiner breaks it down for us
The Human Behavior & Evolution Conference is the best

So it’s worth taking a few minutes to consider what male and female actually are. In genetic terms male and female are strategic options built around gametes—sex cells. A billion years ago when sex was invented two pieces of protoplasmic replicating material (who loved each other very much) decided to join up. They had a special cuddle and discovered that they could fuse their material together—for mutual benefit. Love was born.

Now, it came to pass that once you get into the fusing business there are two paths you can go down. You can favour staying put and storing energy or you can favour moving about and looking for a cell to fuse with. Even tiny differences start to get multiplied over the years. Once you go down the small-and-fast route you have to continue—otherwise you will be out-competed by those who are even smaller and faster. Once you go down the staying put and storing energy route—you have to continue. Otherwise you will be out-competed by those who store better. (6)

Maleness is a sexual strategy built around having small fast-moving gametes. Femaleness is a sexual strategy built around having large energy rich gametes.

And that’s all that they are biologically.

For a variety of social and political reasons, bound up with moralistic and naturalistic fallacies, some people want maleness and femaleness to be either more than that, or less than that. Well, they have to look elsewhere than biology for support for their politics, fine and noble as they doubtless are. Nature doesn’t give two gametes for human narrow-mindedness.

God was a civil engineer. That’s the only explanation for building a toxic waste pipe through a recreation area.

Penises, for example, are mechanisms for transferring gametes. The number of organs that have been co-opted to perform this task across the animal kingdom is truly vast. (7) Spiders use their front limbs (pedipalps), sea slugs have penises in their mouths (8). The paper nautilus fires his penis into the female, leading early biologists to think that the females were infested with a parasitic worm (9). Some snails penis fence to decide who gets to inseminate whom. (10) In a bunch of species, the female transfers genetic material to or from the male—and to do this she often uses a penis. Call it something else if you like but that’s its job. To pretend otherwise is to fall for the most clichéd anthropocentrism.

The following picture shows the major classes by relative size corresponding to number of species in that class. Each animal is a class representative. The very large beetle represents the insects—and Haldane’s quip that god must be “inordinately fond of beetles”. All the mammals—and I assume any of my readers are a sub-class of these-- are represented by the tiny elephant in the foreground.

Still feeling like its all here for our benefit?

Just as it’s hard to study astronomy and conclude that universe is here for our benefit, it’s hard to study biology and think that we are either the reason for life or its only pattern.

Throughout nature you will find organisms that change sex when it suits them (11), species with five hundred different sexes (12), females with penises and phalluses (13), males who get pregnant, species where males dominate a hierarchy, ones where females do, or ones where it seems roughly even-stevens.  How to make sense of all this variety? Here is one, very important way.

When a mummy and a daddy, who love each other very much...

Throughout nature--in two-sex species-- the sex whose minimum potential investment in offspring is the highest is going to be strongly selected to be the pickiest about who it shares its gametes with. In turn, the sex with the lowest minimum potential investment can sometimes afford to be less choosy. Furthermore—this sex will tend to compete for the other sex. (14)  

The logic of this is laid out in Bob Trivers’ seminal (don’t bother, all the jokes have been done) 1972 paper. In it he predicts that species yet undiscovered will fit this pattern and history has proved him right again and again. In many species the minimum potential investor is the male. And, it makes sense that the strategy built around small fast-moving gametes might often be the one that can, on occasion, leave the other sex literally holding the baby.

However, as the great sexologist Milton Diamond loves to point out, “nature loves variety, unfortunately, society hates it”. (15) There are plenty of species where the male’s minimum potential investment is higher than the female’s and in each and every single one of these species Trivers’ prediction has been borne out. In emperor penguins, Mormon crickets, emus, sea-horses, and now this cave insect, the male brings so much extra to the party that the females are pushy and compete for him.

Neotralga mating cut through
The female spines grip so hard that the male was pulled in half when they tried to separate them

Actually, in the case of our cave louse “compete for the males” is an understatement. Her huge spiny penis holds the struggling male in place and extracts his nourishing spermatophore along with his sperm in copulations lasting days. Ouch.

How I met your mother

Humans are a mutually sexually-selecting species. Minimum female investment is high. Pregnancy is long and costly, and used to be very dangerous. Feeding babies with bottles is a recent invention too. However, human males also bring things to the baby shower leading to all sorts of interesting competition between and within the sexes and giving scientists plenty of work to do for years to come.

But--one thing that we keep finding is that, while human males are just as picky as females about long term partners, they can be pretty unguarded about short-term ones.


In a beautifully simple study Clark and Hatfield (16) had attractive students go up to members of the opposite sex on campus. “Hi, I have seen you around campus and I find you very attractive”, they said. “Would you consider…” and then there were one of three offers. [Alternate vid link]

1)      Going on a date with me?

2)      Going for coffee with me?

3)      Going to bed with me?

The numbers who would agree to go on dates or for coffee was roughly even between the sexes. However, the responses to question three were sharply divided along sex lines. 75% of the men said yes, none of the women did. Not one. Nada. Nil. Zero. Less than one. Only someone in the grip of an ideology would be surprised at this. Lots of people—presumably in the grip of some ideology—tried to prevent this finding being published. (17) But, truth will out. This is not to say that human females will not have casual sex. (18) However, they are far from casual about who they will have it with.  

Someone in the grip of an ideology

Im not listening
I refute it thus

Some social psychologists have recently attempted to refute this finding by asking a class of female students whether they would have sex with Johnny Depp if he came up to them and offered. (19) Lots of the students said that they would. This is obviously some new sense of the word “refute” that the rest of us were previously unfamiliar with. Would females consider going to bed with a handsome, rich, and famous man of proven reputation? What is this? A single-question IQ test?

The important question is—do human females, designed over millions of years around a strategy where the minimum cost of a sexual mistake was high, have an inbuilt protection against making the kind of bad decisions that males are perfectly happy to make?

But, since we are doing thought experiments--try the following one on yourself. Man or woman: Imagine that you live in a world without consequences. No reputations to lose, feelings to hurt, diseases to catch, or babies to generate. Got a nice picture?

world without consequences
If you were the last man on earth--you'd still come second

Now. Establish in your head the sex of those you like to have sex with. If you like both sexes—then lucky you—this exercise is going to be even simpler. Line up all your friends of that sex in your mind’s eye. Now, run through in your mind all those friends of that preferred sex and mentally tick off whether you would or wouldn’t have sex with them. Remember--this is in an imaginary world without consequences. Also—it makes absolutely no difference if you are gay, straight or bi. Mentally put those you would have sex with to one side and the rest on the other side. OK? Got a nice clear picture? Give a little wink to the lucky ones. I hope they all wink back. It’s a fantasy, after all. No-one can see you.

18000 ejaculations per second vrs 4.4 births. You do the math.

I can confidently make the following prediction. If you are a boy there are many many more yeses than nos. If you are a girl, there are many more nos than yeses. If you are a straight boy--you just imagined a big crowd of girls winking at you. If you are a straight girl--then there was an equally large crowd of boys looking somewhat crestfallen. Try moving them around. If you are a girl then trying to move a guy from the “no” stack to the “yes” probably resulted in feelings of disgust.

I’ll stick my neck out further. Get an honest friend of the opposite sex to do the same thought experiment so you can compare. I will lay odds that the number of women the man would not have sex with is a smaller number than the number of men the woman would have sex with. A typical straight man’s lists of “woulds” is the same size as a typical woman’s list of “are you feckin kidding mes?”

This doesn’t make men into sexual incontinents who cannot help themselves. However, it does illustrate that women, but not men, have an inbuilt protection against potentially bad sexual decisions. Guys have to use reason and experience. What could possibly go wrong…?

we blame society but we are society
Socially constructed? Out of what?

Brain-washing? A light rinse will do the job.

It’s tempting for a certain kind of person to now go, “That’s as maybe. But sex differences are (merely, it’s always merely) socially constructed”. Ok—let’s accept this as true for the sake of argument. What are these merely social differences constructed out of? At a bare minimum they must be constructed out of thoughts. And any new roles would also have to be constructed out of thoughts. And you—just now—could not even think yourself out of the so-called role you have been assigned. Remember--this was an exercise in pure thought. No-one to peek into your head. No-one to name or shame you. No-one to impress. And if you can’t even think yourself out of being male or female then what on earth would you try to construct an alternative set of socially-constructed sex differences out of?

A recent attempt by someone actually trying to come to grips with how thin the concept of “sex roles” really is, is the journalist Norah Vincent. (20) As detailed in her excellent “Self Made Man” she lived as a member of the opposite sex for over a year, joining sports clubs, going on dates, and getting under the skin of men. I don’t want to give too much away but suffice to say that she went in to the exercise as something of a social constructionist. She emerged as someone who realised that, while sex roles may have a strong element of fashion about them, sex differences are deep-down real. You know what she said? “Women will never get how men think about sex”.

Dresses vs shorts, long or short hair, pink or blue. These are fashions. Differential parental investment, however, goes right down to the chromosomes. (21)

Slugs and snails and puppy-dogs tails

Picky, picky, picky

So what do cave-louse female penises mean for sex roles in humans? Not a lot. If people want to play at cave-louse sex with strap-ons in the comfort of their own bedrooms then it’s no-one’s business but their own.  We are nothing if not a playful species. However, if folk want to see this exciting discovery as anything other than a triumphant vindication of the one of the core principles of evolutionary biology—differential parental investment theory-- then they are woefully mistaken.


1)      http://www.amazon.com/The-End-Science-Knowledge-Scientific/dp/0553061747

2)      http://whyevolutionistrue.wordpress.com/2014/04/19/researchers-report-female-cave-insect-with-grasping-penis-leads-to-accusations-of-sexist-science/

3)      Yoshizawa, K., R. L. Ferreira, Y. Kamimura, and C. Lienhard. 2014. Female penis, male vagina, and their correlated evolution in a cave insect. Current Biology http://dx.doi.org/10.1016/j.cub.2014.03.022

4)      http://io9.com/your-penis-is-getting-in-the-way-of-my-science-1564473352

5)      Donner, J. (1966). Rotifers. Frederick Warne & Company.

6)      For the various ways that this might have come about check out (cannibalism) Sagan, D., & Margulis, L. (1986). Origins of sex: three billion years of genetic recombination; (Infection) Hickey, D. A., & Rose, M. R. (1988). The role of gene transfer in the evolution of eukaryotic sex. The evolution of sex, 161-175; and (genetic repair) Bernstein, H., Hopf, F. A., & Michod, R. E. (1988). Is meiotic recombination an adaptation for repairing DNA, producing genetic variation, or both. The evolution of sex, 139-160.

7)      Eberhard, W. G. (1985). Sexual selection and animal genitalia.

8)      Sapha amicorum genitalia Marcus 1959 Marcus, E. R. N. S. T. (1959). Eine neue Gattung der Philinoglossacea. Kieler Meeresforschung, 15, 117-119. Penis in mouth of sea slug

9)      Müller, H. (1853). Ueber das Männchen von Argonauta argo und die Hectocotylen. Zeitschirift für Wissenschaftliche Zoologie, 4, 1-35.

10)  Koene, J. M. (2006). Tales of two snails: sexual selection and sexual conflict in Lymnaea stagnalis and Helix aspersa. Integrative and comparative biology, 46(4), 419-429

11)  Judson, O. (2002). Dr. Tatiana's Sex Advice to All Creation: The Definitive Guide to the Evolutionary Biology of Sex. Macmillan. This excellent work should be a primer on any sexuality course. I use it as one in mine.

12)  Bailey, J. (1997). Building a plasmodium: development in the acellular slime mould Physarum polycephalum. BioEssays, 19(11), 985-992.

13)  Kruuk, H., & Kruuk, H. (1972). The spotted hyena: a study of predation and social behavior (p. 335). Chicago: University of Chicago Press.

14)  Trivers, R. (1972). Parental investment and sexual selection.

15)  http://www.hawaii.edu/PCSS/

16)  Clark, R. D., & Hatfield, E. (1989). Gender differences in receptivity to sexual offers. Journal of Psychology & Human Sexuality, 2(1), 39-55.


17)  http://www.realclearscience.com/blog/2014/04/would_you_have_sex_with_an_attractive_stranger_.html

18)  Vrangalova, Z. (2014). Does Casual Sex Harm College Students’ Well-Being? A Longitudinal Investigation of the Role of Motivation. Archives of sexual behavior, 1-15.

19)  Eagly, A. H., & Wood, W. (2013). The Nature–Nurture Debates 25 Years of Challenges in Understanding the Psychology of Gender. Perspectives on Psychological Science, 8(3), 340-357. They cite Conley, T. D. (2011). Perceived proposer personality characteristics and gender differences in acceptance of casual sex offers. Journal of Personality and Social Psychology, 100, 309–329. This position was first exposed as absurd by Aaron Sell http://www.psychologytoday.com/blog/evolutionary-entertainment/201308/is-why-conservatives-don-t-believe-in-global-warming

20)  Vincent, N. (2006). Self-Made Man: One Woman’s Journey into Manhood and Back. New York: Penguin. She is interviewed here

21)   Cronin, H. (1993). The ant and the peacock: Altruism and sexual selection from Darwin to today. Cambridge University Press.

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