C-sections haven’t been shown to change human evolution

Everyone and their mother is sending me this story today: C-sections May Be Changing the Course of Evolution.

Rates of caesarean section are increasing in countries like the U.S. and the U.K. and a new study suggests that more and more women need the surgery because of their narrow pelvis size — a trait that evolution would, in theory, have weeded out.

For the paper, published in the journal Proceedings of the National Academy of Sciences, researchers used data from the World Health Organization and other large birth studies and determined that cases where the baby is too big for the birth canal — a.k.a. obstructed birth — have increased from about 30 per 1,000 in the 1960 to 36 per 1,000 today.

I say the paper doesn’t show a causal relationship.

Has the rise in C-sections affected human evolution? This scientist predicts yes.

Human ingenuity increasingly allows us to fight back against “natural selection” and, in effect, influence the path of our own evolution.

Take Cesarean sections, the procedure in which babies are born via surgical incision rather than through the mother’s birth canal. Some form of the procedure has been around for hundreds of years, but only in the past few decades has it become commonplace.

In the US, C-sections now account for 30 percent of all births, according to the Centers for Disease Control and Prevention. But back in 1970, that figure was around 5 percent. So while C-sections have only been widely available to mothers for just a couple of generations, already scientists are speculating that the procedure is affecting human evolution.

This scientist says probably not.

The paper itself argues for obstetric selection in humans.

Compared with other primates, human childbirth is difficult because the fetus is large relative to the maternal pelvic canal. It is a long-standing evolutionary puzzle why the pelvis has not evolved to be wider, thus reducing the risk of obstructed labor. We present a mathematical model that explains the high rates of fetopelvic disproportion by the discrepancy between a wide symmetric phenotype distribution and an asymmetric, “cliff-edged” fitness function. Only weak selection for a large newborn, a narrow pelvis, or both is necessary to account for the high incidence of fetopelvic disproportion. Because the regular use of Caesarean sections has reduced maternal mortality, the model predicts an evolutionary response of fetal or maternal dimensions, increasing the rates of fetopelvic disproportion.

Nah, not buying it.

Actually, they do do what they say: they present a mathematical model of how a disparity between head size and pelvic canal size could hypothetically lead to a selection effect, given a particular frequency of disproportion. They don’t actually measure or observe anything, though. They pull together a number of factors, like the heritability of pelvic and head size, and estimates of the frequency of serious birthing difficulties, etc., all of which show a wide range of reported values, and then put together an abstract series of calculations to show that hey, this could potentially have an effect. That’s it. Don’t panic. We’re not looking at an imminent future of bulbous-headed babies and pencil-hipped women because we’ve removed an important constraint on selection.

Without criticizing their calculations, I have to point out that their assumptions (which to their credit they do note) are faulty. You can’t assume from the frequency of Caesarian sections that there is an equivalent frequency of pelvic diameter – fetal head size disparity. C-sections are an extremely indirect measure of that parameter, one that is prone to all kinds of irrelevant noise…I mean, cultural influences.

Here, for instance, is the frequency of c-sections by country.

csectionfreq

Do you think Turkey and Mexico have huge numbers of giant-skulled babies straining to burst out of their slender-boned mommas? Or that in Sweden and the Netherlands they have more pin-headed babies that slip lightly from their mothers’ gargantuan hips?

Or maybe, just maybe, some significant number of c-sections are unnecessary surgeries, and the differences represent nothing but different biases in medical practice? (However, if your doctor advises that you need one, don’t let this fact dissuade you. You might be one of the people who really, really needs a c-section.)

The World Health Organization has reported that in many countries, c-sections are done at an excessive rate, and that above a certain level, c-sections do not reduce negative effects.

Several studies have shown an inverse association between CS rates and maternal and infant mortality at population level in low income countries where large sectors of the population lack access to basic obstetric care. On the other hand, CS rates above a certain limit have not shown additional benefit for the mother or the baby, and some studies have even shown that high CS rates could be linked to negative consequences in maternal and child heath.

Bearing in mind that in 1985 the World Health Organization (WHO) stated: “There is no justification for any region to have CS rates higher than 10-15%”, we set out to update previous published estimates of CS rates worldwide, and calculate the additional number of CS that would be necessary in those countries with low national rates as well as the number of CS in excess in countries in which CS is overused.

This means that c-section frequency is a really bad proxy for a selection pressure. Note also that the United States’ c-section rate is well above the reasonable frequency. That 25% increase in the rate here probably does not represent any significant change in the degree of selection going on.

The math is nice, but it’s poorly rooted in any real biological phenomenon. Although it turns out that making predictions about evolving babies is a good way to get oodles of press.

Susan Mazur vs. Carl Zimmer? Really?

There was a Royal Society meeting that I mentioned rather disparagingly — it was on extending the neo-Darwinian evolutionary synthesis, as presented by people who didn’t understand the neo-Darwinian evolutionary synthesis. I wasn’t there, but Carl Zimmer was, and he gave a fair summary of the criticisms of the presentations. Zimmer has always been a first-rate science journalist, and I wish we had a few hundred clones of the guy.

Susan Mazur is someone I’ve described as a journalistic flibbertigibbet who never met a crackpot critic of evolution that she couldn’t fluff up with sensationalist hyperbole. She loved Stuart Pivar’s work. She hyped the Altenberg 16 meeting. She doesn’t seem to understand any biology at all, and is not interested in learning any — she seems more concerned with getting the approval of ‘controversial’ flakes, in the forlorn hope of being the first to report on radical breakthroughs.

Mazur also reported on the Royal Society meeting. Or at least, as Larry Moran explains, she reported extensively on the presence of Carl Zimmer at the meetings. You want to see white-hot professional jealousy screamingly displayed, go read her post. It’s embarrassing. Would you believe she wrote a whole book, Royal Society: The Public Evolution Summit, about the meeting before the meeting? Now she’s bitter that she can’t get her stories about the Paradigm Shift she predicted would take place published, and she’s particularly bitter that mainstream, consensus critics of her imaginary revolution presented at the meeting. How dare they ruin her innovative auto-da-fé?

Somewhat surprisingly, she’s particularly irate with all the Templeton-funded scientists who presented there.

Ten of the 26 presenters were part of the John Templeton Foundation-funded Extended Synthesis project. Templeton is known for its pairing of science and religion. And as the talks proceeded, it appeared to some in the room that the JTF-funded scientists had both compromised their work and retarded science by accepting the foundation’s easy money.

That sounds like something I’d say, except that her complaint is that those scientists, by accepting the mediocre science of modern evolutionary theory, were acting contrary to its [Templeton’s] “spiritual” mission.. I know, we’re in the bizarro world.

Mazur only found a few things she like about the meeting, and of course they were the weirdest, farthest-out proponents of the wrongest ideas: James Shapiro and Denis Noble.

James Shapiro, the other bright spot of the RS meeting, highlighted themes from his book, Evolution: A View from the 21st Century, regarding symbiosis and hybridization and waded into the water on viruses, talking about their role in formation of the eye and the placenta. I addressed a question to Jim Shapiro about stem-loop RNAs (viruses), which Shapiro said he was “challenged by.”

The other notable conference news was Denis Noble citing the embryo geometry paper of Stuart Pivar, who was seated in the room between wife Larimore and co-author David Edelman and elegantly dressed in a black velvet jacket for the occasion. Pivar has faced fierce criticism in the past regarding his evolutionary perspective, particularly from the PZ Myers pack, and so welcomed Denis Noble’s recent invitation to publish in Progress in Biophysics and Molecular Biology, one of the journals Noble co-edits. Noble is also listed on the “advisory panel” for Pivar’s new web page: urform.org.

With so much exciting evolutionary science now openly accessible online, it is disappointing and most peculiar, that this meeting about supposedly “new trends” squandered an important opportunity to deliver that to the public and instead served largely to reinforce standard thinking on evolution.

Well hello, pack! You got a shout-out!

You know, if Carl Zimmer were writing this kind of summary, he’d explain what stem-loop viruses are, maybe actually say what challenging question he asked, and he’d note something other than Pivar’s choice of a jacket. This is exactly why Mazur is such a horrible writer about biology.

But just for an example of really bad journalism, read Mazur’s 2000 word hate-rant against Carl Zimmer. Be like Carl. Don’t be like Susan.

Tardigrade sex

You may have suffered many restless nights wondering how tardigrades had sex. It’s one of those burning questions that I’m sure has left many of us curious and concerned. Wonder no more! We have tardigrade porn!

In case you’re confused, here’s the text description of what’s going on in that video.

When put together with gravid females, males seemed to be attracted, moving directly towards the female and joining her for mating. On rare occasions males were not attracted to females, and this presumably occurred when females had started to absorb eggs. For mating, the male curled around the anterior end of the female exuvia, bringing his cloaca close to the mouth opening in the exuvia (Fig. 2). During mating he held the female with his first pair of legs, and the female stimulated the male by moving her stylets and contracting the sucking pharynx. Mating took about 1 h, and semen was ejaculated several times (visible under the light microscope). Exactly the same mating behaviour was observed more than 30 times in more than 30 tardigrade couples, and mating was also documented on video.

Still confused? Perhaps it would help to know that they’re bisexual, and there aren’t any anatomical differences between the sperm-producing male and the egg-producing female. Here’s a close-up of their external reproductive organs.

Cloaca (indicated by arrow) of two individuals of Isohypsibius dastychi. The cuticle opens anteriorly. A, cuticle covering the cloaca is pushed towards posterior end of the animal. B, cuticle in the natural state. Scale bar = 10 μm.

Cloaca (indicated by arrow) of two individuals of Isohypsibius dastychi. The cuticle opens anteriorly. A, cuticle covering the cloaca is pushed towards posterior end of the animal. B, cuticle in the natural state. Scale bar = 10 μm.

Surely everything is clear now! Just in case, here’s a simplified diagram of the Standard Tardigrade Sexual Position.

Mating position of Isohypsibius dastychi. The male (left) held the female (right) in the moulting stage, with eggs (in this case three) clearly visible in her ovary.

Mating position of Isohypsibius dastychi. The male (left) held the female (right) in the moulting stage, with eggs (in this case three) clearly visible in her ovary.

Distressing thought: if you are a tardigrade, it looks like you can get pregnant from oral sex.


Bingemer J, Hohberg K, Schill RO (2016) First detailed observations on tardigrade mating behaviour and some aspects of the life history of Isohypsibius dastychi Pilato, Bertolani & Binda 1982 (Tardigrada, Isohypsibiidae). Zoological Journal of the Linnean Society 178(4):856-862.

You don’t get to revise evolutionary theory, until you understand evolutionary theory

There was a conference sponsored by the Royal Society last month, titled New trends in evolutionary biology: biological, philosophical and social science perspectives. There have been a number of news stories about this event, some good, some bad. Here’s one: can you tell what’s wrong with it?

For example, speaking at the Royal Society was Melinda Zeder, who talked about the way in which modern synthesis fails to provide a reason for mankind’s turning to agriculture 10,00 years ago and its ensuing evolutionary impact. Growing crops may have taken years, so there could not have been a short-term evolutionary benefit to it. As Zeder told Quanta, “You don’t get the immediate gratification of grabbing some food and putting it in your mouth.” It’s also been theorized that a climate shift caused agriculture to bloom, but there’s no evidence of such a shift.

[Read more…]

Try telling Ray Comfort that

He won’t get it, because like a heck of a lot of people, he doesn’t understand systematics at all. We will continue to try, though. Here’s a simple introduction to a basic concept in cladistic taxonomy:

One of the central tenets of modern taxonomy is that every group has to include, by definition, all of the groups that evolve from it. So rats did not stop being mammals when the rodent group branched off the evolutionary tree. Every branch on the tree of life is considered to be a member of all its parent branches.

This means, for example, there can be no definition of fish that does not include everything that evolved from fish. Following this logic you could argue that as amphibians evolved from fish, amphibians are fish. Mammals evolved from animals that evolved from amphibians, so mammals are fish. We are fish. While every biologist knows this conundrum, and that there is no biological definition for what most people consider “fish”, they decide not to worry about it because it’s helpful to think about living swimming “fish” as a group. Taxonomy is useful and makes a lot of sense, until it doesn’t.

There are other ways to classify organisms — we could do it by what color they are, or what they eat — but the one method that works coherently is to group them by line of descent.

The righties get their scientific misinformation from Breitbart, the Daily Mail, the Drudge Report, and James Delingpole

This is what we’ve come to already.

The house science committee, chaired by Republican Lamar Smith, is citing an article in Breitbart written by James Fucking Delingpole. It’s a story built on a collection of lies first published in The Daily Mail.

The Washington post calls it “dubious and deceptive”, and has published an article rejecting the claims, Earth’s temperature has not plunged at record clip and nationwide record cold not coming. The scientists I know are dumbfounded.

I actually read Delingpole’s article, and even though I’m not a climatologist, I could see how thickly the bullshit was being slathered. Here’s the kind of nonsense he’s slinging.

This is why there is such an ideological divide regarding climate change between those on the left and those on the right. The lefties get their climate information from unreliable fake news sites like Buzzfeed.

Wrong. This lefty gets his climate information from published, peer-reviewed science.

I get email…from Stuart Pivar!

He rankles easily, and my criticisms of his imaginary gastrulation paper demanded a reply…so Pivar rather haughtily wrote to me and is putting together an addendum to his paper. I pointed out that none of his fancy drawings corresponded at all to any gastrulating embryo, and that there is an utter lack of evidence for any of his hypothetical stages.

His answer? He meant to do that.

You see, he’s illustrating lost stages of embryonic development, stages that were modified by evolutionary changes like condensation (the compression of developmental events), and so modern animals don’t look like that.

We well know the difference between observed embryology and the proposed ancestral model now absent due to the phenomenon of condensation (see Gould, Ontogeny and Phylogeny, 1977)) . The attached paper accounts for the difference.

To publish illustrations without text is like watching the opera with no sound.

Well, sure, but when the opera music is screeching cacophony, and the libretto is a word salad, but the scenery and costumes are spectacularly silly and flamboyant, you’re doing the show a favor by turning off the loudspeakers.

OK, but I’ll just show you some of the words from his submitted addendum — I don’t need to show you the pictures, since they’re just the same imaginative squiggles we saw in the first. He still doesn’t answer what should be the central question of any science paper: how do you know your explanation is valid? Where is the evidence, the data, behind your results? It’s fine to say you’re describing stages or organisms lost to evolutionary history, but then you have to explain how you figured out the missing pieces of the puzzle. He doesn’t.

Actually, all his addendum does is reveal some weird preconceptions that Pivar has, like this:

A previously published paper (Pivar, et al., 2016) attributes the origin of vertebrate form to a hypothetical, lost initial stage of development consisting of the geometrically regular arrays of cells in the blastula resulting from the binary subdivision of the egg through the three axes of space in a coherent sequence of mechanically caused configurations. The sequence is interrupted by the bursting of the hypertense blastula along its ventral midline, followed by the elastic recoil of the surface toward the dorsal midline. This paper examines this event, demonstrating that the embryo is a resulting temporary form, consisting of the compressed form of the blastula—the limbs, ribs, and spine compressed into small bales, the limb buds and somites. Fetal development consists of the gradual resumption of the forms prior to recoil-compression.

Think about that. He’s trying to describe a universal property of vertebrate embryos, which means he has to be discussing a Pre-Cambrian state. But he’s listing derived characters — limbs, ribs, spine — that would not have been present in that “lost” ancestor, and he’s claiming that those characters were actually there, in a compressed form, ready to burst out in developing forms.

We have a word for this. He’s describing preformation. It’s not valid. That’s not how development or evolution work.

He’s also describing forces — “hypertense”, “elastic recoil”, “recoil-compression” — that he does not measure in any way but simply assumes are present. Again, how do you know that? He doesn’t say.

The concordance of this proposed hypothetical blueprint for the development of the vertebrate body with observed embryology is based on the principle of condensation, where over eons of evolutionary time terminal stages are added to embryology while initial stages condense and eventually disappear. Here the sequences, called embryogenesis, are observed embryology, while morphogenesis constitutes a hypothetical reconstruction of initial stages lost to evolutionary condensation.

The stages disappeared! So how do you know what they were? “Hypothetical reconstruction” is not sufficient explanation, especially when those reconstructions lack any “concordance” with the embryology of modern forms. You don’t simply get to do it because you think it looks right.

For example, I never met my paternal grandfather. I never even saw any photos of him — he died when my father was a little boy. I have seen photos and other records of more distant relatives, thanks to genealogy-obsessed aunts. So my grandfather is a “lost” ancestor.

family

By Pivar-logic, though, I get to ignore all known states and ‘hypothetically’ reconstruct Grandpa in whatever way looks good to me.

hypfamily

I suspect this is probably incorrect, especially since I can’t justify it with evidence in any way.

Oh, except if you use “inductive-deductive reasoning” to claim that it is plausible!

The presentation of the theory engages the Cartesian method of inductive-deductive reasoning to discover a mechanically plausible hypothetical path of cell division that accurately predicts the forms of the organism. The result is a coherent roadmap that directs evolution and guides the generation of the complex body from a single cell.

No, it is not coherent, nor does it accurately predict anything! Show your work, Pivar. It is not enough to say that you can distort your colored blobs into new shapes; you have to show how you know they did that, and relate them to modern forms…which you can’t do, because you lack any understanding of modern developmental biology.

Note how he closes the paper.

This presentation is in the form of a non-rigorous schematic, mechanically, geometrically-based sketch. The authors invite the multitudes of parties interested in the subject to participate in the corroboration (or refutation) of the premise by further investigation by theoretical, computational, and laboratory research.

Remarkable. His work is not rigorous, is based on playing geometry games with sketches, and he admits it. And then he asks other people to justify his premises for him with real research, which he hasn’t done.

I’ll pass.

I do notice, though, that he forgot “silence critics with lawsuits” as one of his strategies for testing his premises.