Clitoral kludges

My favorite argument against Intelligent Design is the fact that the clitoris is located nowhere near the cervix — for women, reproduction and recreation are fairly effectively uncoupled. But that doesn’t stop some people from imagining the existence of a vaginal source of sexual pleasure, the G-spot. I don’t believe it exists; I do believe that individuals can be sexually stimulated by contact in all kinds of places, from vagina to toes to neck to belly-button, that it varies from person to person, and that you don’t need to find an excuse in sloppy anatomy to justify what makes you feel good.

But I also think it’s an interesting example of chance and contingency in evolution. It would optimize the likelihood of reproduction if women could only find sexual gratification by stimulation deep in the vaginal canal — they’d be more likely to encourage sexual penetration. But the homologous tissue to the penis in women is the clitoris, which is in a fine position for creative external stimulation, but less than optimal for stimulation during intercourse. It’s location is clearly the result not of selection for the function of encouraging female orgasm during reproduction, but as a byproduct of selection for males’ interest in penetration during sex (females have sensitive clitorises because males have sensitive penises), which does enhance reproduction.

So it’s a good article highlighting a weird masculine desire for the vaginal orgasm, but it also illustrates that a fortuitous feature of female anatomy isn’t there for baby-making: it’s there for fun. O happy kludge, I’m so glad you’re there.

Are some of you haunting the Blaze polls?

I ask because they have an indignant article up about how the air force is no longer requesting that any lodging they use have bibles in the room — and the associated poll is already going the godless way! That’s just not like the Blaze.

Is the Air Force right to remove the Bible requirement?

Yes. 70.3%

Nope. 28.82%

I’m in the middle on this one. 0.87%

I’m feeling redundant. In a good way.

Adding space dinosaurs can draw attention to your sins

That ridiculous paper that postulated alien dinosaurs has another flaw, to the detriment of an otherwise well regarded researcher: Ronald Breslow has been accused of self-plagiarism. It seems to be true, too; examples show that he has been recycling substantial chunks of text in multiple papers.

I guess that’s how the big names can generate those impressive publication lists: they just recycle each paper a few dozen times.

Christian love

A Christian prayer group really doesn’t like the Military Religious Freedom Foundation.

Now for our prayer, we pray that the women who work in your MFRR and the women in your family will befall fast moving breast cancer which can not everbe cured. We pray this for Leah Bruton, and Becki Miller, Patricia Corigan, Chris Rodda, Edie Disler, Vicky Garrison, Kristin Leslie, Melinda Moeton and Joan Slish. And you evil clan too, we pray this for Bonnie Wiensten and Amanda and Amber Wienstein and the woman lawyers Cariline Mitchel and Katherin Ritchy and all women of all who work at with for Military Freedom Against Religon Foundation.

The women targeted have nothing to worry about — you can’t get much more ineffective than sitting around wishing a nonexistent ghost would afflict your enemies — but the sad thing is that the women in this prayer group really believe in the efficacy of their magic incantation, and honestly want other women to suffer horribly from a painful, disfiguring, and life-threatening disease.

You shall know them by their love. Their blind, hateful, petty love.

Modular gene networks as agents of evolutionary novelty

A while back, I told you all about this small piece of the biochemistry of the fly eye — the pathways that make the brown and red pigments that color the eye.

I left it with a question: if even my abbreviated summary revealed considerable complexity, how could this pathway evolve? Changing anything produces a failure or change in the result. Before I answer, let’s make the problem even harder, because I love a challenge (although actually, I’m cheating — it’s going to turn out that complexity is not a barrier, but an opportunity).

The pigment pathways above are far downstream: they operate in the differentiated compound eye of the fly. Long before that, there are a set of genes that have to be activated first to trigger formation of the head and eye in the larva. And this is that pathway:


Regulatory scheme on the top of the eye developmental pathway. Twin of eyeless (toy), eyeless (ey), and possibly eyegone (eyg), three Pax genes, are master control genes on the top of the hierarchy. Sine oculis (so), eyes absent (eya), dachshund (dac), and optix are second-order transcription factors regulated by the master control genes. Note that the pathway is not linear, but rather a network interconnected by feedback loops.

At the top of the hierarchy are two genes in Drosophila, eyeless (ey) and twin of eyeless (toy). Remember, genes are named for their mutant effect, so the normal function of eyeless is to initiate eye development. These genes switch on sine oculis and eyes absent (notice the effort to find synonyms to describe genes that cause missing eyes when broken) that activate each other and feed back on eyeless to generate a robust response. Another gene, dachshund (this one named for another part of its phenotype: it makes flies with very short legs) also feeds back on eyeless.

This circuit has multiple outputs: so, dac, optix and eyg. All of these have effects further downstream, in that catch-all category labeled “eye development” here. In that broad label lie multiple processes: the pigment pathways above, but also all kinds of elaborate interactions that recruit cells to specific photoreceptor functions, that organize supporting cells, like hair cells and lenses, and that induce the neural tissue of the retina and deeper parts of the nervous system. The genes ey and toy initiate a whole deep, branching network of genes that cascade together to build the many bits and pieces of the eye.

These two master control genes, eyeless and twin of eyeless, also have a synonym. To everyone’s surprise, versions of this circuit are found in all animals with eyes, and the common name for this universal regulator of eye formation is Pax6, and that’s what I’ll call it in the rest of this article.

And look at this! Isn’t it cool? All these eyes use this same Pax6 gene regulatory network to initiate development.


General scheme of eye evolution. The first step in eye evolution is the evolution of a light receptor molecule which in all metazoans is rhodopsin. In the most ancestral metazoa, the sponges, a single Pax gene, but no opsin gene has been found. In the cubozoan jellyfish Tripedalia, a unicellular photoreceptor has been described in the larva. The adult jellyfish has complex lens eyes that form under the control of PaxB, whereas the eyes of a hydrozoan jellyfish (Cladonema) are controlled by PaxA. We propose that from the unicellular photoreceptor cell, the prototypic eye postulated by Darwin originated by a first step of cellular differentiation into a photoreceptor cell and a pigment cell, controlled by Pax6 and MITF, respectively. From this prototype, all the more complex eye types arose monophyletically. As a mechanism, we propose intercalary evolution of progressively more genes such as lens genes into the eye developmental pathway (after Gehring and Seimiya 2010). Starting from the common prototype, the various eye types evolved by divergent, parallel, and convergent evolution, generating a magnificent biodiversity.

That’s the power of a gene regulatory network. Switch on just one of the key genes, and it recruits all the downstream genes and triggers a whole series of actions to assemble a complex structure. That strange grey object to the right is a developing Drosophila wing — the dark fringe is the line of bristles that surround the leading and trailing edges of the fully-formed wing — which has had the Pax6 gene inappropriately expressed in a few cells at the base. Just switching on that one gene has led to the construction of an eye with its red pigment right there, where flies should not have eyes.

The ability to build elaborate organs with a simple switch is a reflection of the modular nature of developmental programs. It also simplifies evolution; small, simple changes can lead to dramatic novelties. Zap, one mutation can lead to an abrupt saltational change.

Now wait a moment, you will say. Suddenly plopping an eye onto a wing sounds disastrous: it really is a kind of hopeful monster, emphasis on “monster”, and is almost always going to be grossly deleterious. This can’t be a viable pathway for evolutionary change, can it? And you’d be right. But what about portions of a pathway? Look back up at the eye development pathway, the second figure in this article. What if you just switched on optix, one of the second-order transcription factors? Then you’d just activate some of the tools of eye construction.

It’s been done. The hideous blob to the left is the nascent antenna of a fruit fly, and optix has been inappropriately switched on…and what do you get? It activates the pigment pathway (that biochemical sequence illustrated in the first image at the top of this page), and it creates a bright red spot on the antenna. This is non-trivial; it means the precursors and transporters are all at work, and all the enzymes in the xanthomattin and drosopterin pathways are doing their job. One switch, and you get a whole hierarchy of genes producing a complex output. This could be one way new traits appear, by redeploying genes from established pathways.

Saying they could isn’t the same as saying they did, of course. But here are a few examples that suggest that eye network genes have been redeployed to create morphological novelties. In Heliconius butterflies, for instance, the red spots on their wings can be traced back to embryonic patterns of expression of optix in the developing wings.


Heliconius butterflies express optix in wing epidermal cells that will produce red ommochrome pigments. A: Heliconius erato. B: Forewing and hindwing patterns from different races of H. erato (top: H. e. petiverana; bottom: H. e. erato). C: Pupal wings expressing optix mRNA in a pattern corresponding to the areas of red pigment in wings depicted in (B).

Even more dramatically, here’s an extinct biting midge preserved in amber, and look at that wing: what was I saying about switching on eye genes inappropriately in the wing would be deleterious? I was wrong. This is an insect with a compound eye growing in its wing.


A. The extinct biting midge, Eohelea petrunkevitchi, with a unique wing organ that resembles the surface of its compound eye. B: The dorsal surface of the wing organ. C: The midge’s compound eye. D: The ventral surface of the wing organ.

It’s extremely unlikely that that alar eye functioned as a visual organ: any photoreceptor signals coming from a platform flapping several times a second would be hopelessly confusing. Most likely what it was was a species-specific sexual signal, like the spots on many fly wings — this one is just more elaborately structured and expensive than most. Alternatively, one hypothesis for the formation of spots on insect wings is that they are intended to resemble eyes — large eyes, far apart, making the animal look much larger to predators — so Eohelea may have just been carrying the eyespot mimicry to an extreme. Either way, building these eyes is developmentally trivial.

It may also represent a transitional state: first the initiator of a genetic cascade is co-opted and expressed at a novel time or place, and then selection can hone it down over time, adding new control points that, for instance, suppress irrelevant ommatidium formation in the alar eye while allowing the functional pigment expression to continue.

One last example: this is the Cambrian worm, Microdictyon. Notice anything unusual?


Microdictyon sinicum, a Cambrian Lobopodian fossil from Chengjiang (China) with compound eye on every annulus (segment) above every leg. (A) Reconsruction (after Bergström and Hou). (B) Lateral view.

There’s a pair of eyes in the head, where you’d expect them…but all those other eyes along the sides are morphologically indistinguishable from the anteriormost pair. There is some argument about whether these structures actually are eyes, but they are definitely hexagonal arrays that closely resemble the hexagonally structured ommatidia of the compound eyes of insects. If they weren’t functional eyes, it seems likely that they are at least produced by the redeployment of the structural genes of the compound eye.

And if they were functional eyes, well, that is just freakin’ cool.

The bottom line, though, is that because complex developmental networks are functionally constrained — think of them as software modules that respond to molecular inputs and produce morphological outputs — their complexity is not a barrier to evolution at all, but instead provide opportunities for generating interesting evolutionary novelties.


Gehring WJ (2012) The animal body plan, the prototypic body segment, and eye evolution. Evolution & Development 14(1):34-36.

Monteiro A (2012) Gene regulatory networks reused to build novel traits. Bioessays 34:181-186.

(Also on Sb)

Why I am an atheist – Wayne Schroeder

I was raised as a Christian, but gained my free thought in my teenage years, in the late 1960s. My father was a minister in a moderate protestant church, the Evangelical United Brethren (which merged with the Methodist church in 1968), and I was a believer in my early life, like the rest of my family, friends, and all of society it seemed. But as I learned about evolution I began to question the need for God to explain much of the world. I was taught that evolution was the how but God was the why, but that didn’t seem very plausible. Over the course of a few years, a world without god started to seem more likely. My breakthrough though was finally discovering that there are people in the world who do not believe in any god, that it is possible to be an atheist, and realizing that, it fell into place that that was my world view too. John Lennon’s “Imagine” and the rock opera “Jesus Christ Superstar” are wonderful.

I’m an atheist because there is overwhelming evidence that there are no gods. There are many lines of evidence but an important one for me is that when you rationally and dispassionately consider religious development, it is clear that people create gods, not vice versa. The more distant the cultures, the more different the religions but if people were actually perceiving reality, they would not. Religions battle each other and evolve, each striving to gain and retain believers. Dispassionate reasoning, not religious/emotionally thinking, is a better way separate truth from fiction.

The scientific method is clearly humanity’s most effective way to discover actual truth. To see how well it works, you only have to consider the the wonders of our technological society and compare life in it now to times and places where religion rules. Scientific understanding has been displacing religious beliefs over the last few centuries. It was once believed that a god or gods caused disease, rain, drought, the apparent movement of the sun, even life, death, a lots more. We certainly don’t know everything, but we know and understand a great deal more than the ancients did.

There is some comfort in religion, as most all of us would like to live beyond death, but believing something doesn’t make it so. Truth is more important than comforting falsehoods, and is better for us as individuals and for society as a whole. People have many ways of deluding themselves into believing what they want, so we need to avoid those tendencies, via skepticism and critical thinking.

At the same time, there is great beauty, wonder, and mystery in the real world; the fact that we, and all life, evolved here on Earth over billions of years, that there are billions of galaxies with billions of stars in each, that the atoms of our bodies were formed in stars (which flow through us like water in a stream), etc, etc, etc. It’s really sad that some people avoid seeing reality, in this one life we know we have, for a hope in a life after this.

Wayne Schroeder
United States

I propose that states seize all the Catholic schools

I will never understand Catholicism. On the one hand, they claim to be all about the babies: procreate wildly, let nothing interfere with the spawning. On the other hand, though, they promote deep ignorance and confusion about sex and reproduction, as if they’re afraid of it.

So here’s this lovely case of a teacher at a Catholic school in Indiana who was evaluated as excellent in her work, but who, in her lawfully married and entirely conventional life with her husband at home, wanted to have children — something that ought to be fully copacetic with Catholicism. Except…she had a medical condition that made her infertile, so she and her husband were going through in-vitro fertilization.

Which meant, of course, that the priest at the local Catholic church had the right to meddle.

“On May 24, 2011, Herx, her husband, and her father met with Msgr. Kuzmich and [St. Vincent Principal Sandra] Guffey,” the complaint states. “Msgr. Kuzmich repeatedly told Herx that she was a ‘grave, immoral sinner‘ and that it would cause a ‘scandal’ if anyone was to find out that St. Vincent de Paul had a teacher who received fertility treatment. Msgr. Kuzmich told Herx that this situation would not have occurred had no one found out about the treatments, and that some things were ‘better left between the individual and God.’”

The end result: despite the priest saying that “her performance had nothing to do with the decision to terminate her employment”, she was fired for “improprieties related to Church teachings or Law.” An appeal farther up the hierarchy failed as well, because she’s just plain evil.

“Bishop Rhoades refused to renew Herx’s contract, stating that ‘The process of in vitro fertilization very frequently involves the deliberate destruction or freezing of human embryos,’ and ‘In vitro fertilization … is an intrinsic evil, which means that no circumstances can justify it.’ Herx’s appeal to the Bishop was the final step in the administrative appeals process within the Diocese.”

There’s a bit of lashing out going on now, too.

Herx says she was fired even though the defendants still employ teachers who do not regularly attend Catholic mass; who are divorced (including Guffey); who have had hysterectomies, vasectomies and other procedures that have altered their reproductive organs; and who use contraceptives.

Nobody should be fired for those things, either.

It seems to me that the problem is that the church is playing the role of a secular employer in what ought to be a secular profession, the education of children, while trying to impose arbitrary and obsolete medieval religious rules on its employees. I propose a simple change: seize the Catholic schools, remove the priests from control, and manage them as assets of the community’s public school system.

Do this everywhere for all religious schools, not just the Catholic ones. The strengths of those schools have always been in the teachers, not the dogmatic nitwits in the religious hierarchy who mismanage them. It also ought to be considered a violation of basic civil rights when an employer decides that they have the power to regulate the private, personal behavior of all employees at all times, even when they are not on the employer’s time and property — they have no right to interfere to such an egregiously excessive extent.

The Texas State Board of Education stars in a movie

If you’re wondering why Don McLeroy was on Colbert, here’s your answer: he’s one of the subjects of a new documentary, The Revisionaries. Note that the documentary isn’t his, he’s the king clown exposed in it…and somehow he thought that being targeted this way was a good thing, and that it was a smart move to appear on Colbert for it.

Hey, do you think that if McLeroy showed up at a theater showing the movie, he’d get expelled?