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.

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.

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.

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

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.

I neglected to include another bit of foolishness from that ridiculous Pivar paper. This is a perfect example of “looks like” biology, which is all the paper is: drawing correspondences by saying X looks like Y, based on superficial morphological similarities, and worse, then announcing that because X looks like Y, you have therefore explained both X and Y.

Behold, Figure 20!

Eyeballs and testicles, they’re both paired spheres dangling from stalks, am I right? Therefore, just pointing that rough similarity out simultaneously shows that they are produced by the same process, and explains how they developed and evolved. Done! Gimme my Nobel prize!

The crackpots are bustin’ out all over — not just in politics, but also in science. Remember Stuart Pivar? The septic tank tycoon who invented a whole new theory of evolution and development that he called Lifecode, built entirely around imaginary drawings of how embryos formed by folding and stretching themselves like balloon animals? It was total nonsense. There was no data. Much of his imagined topological transformations contradicted known embryological patterns, and he’d clearly never looked at real embryos. It was loosely based on structuralism, like the work of D’Arcy Thompson, which I consider useful and interesting, but it ignored all the work of the last century on induction and cell signaling and gene regulation. Trust me on this, no modern renovation of evo-devo will be able to just wave away gene and molecular interactions shaped by genetic variation as irrelevant, but that’s what Pivar has done.

I should also disclose that Pivar filed a lawsuit for $15 million against me in 2007, which he dropped as it threatened to become big news. Dang. What is it with people wanting millions of dollars from me?

Anyway, Pivar has a new publication! In the Elsevier journal Progress in Biophysics and Molecular Biology! With new coauthors!

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