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Are Caesarian Sections Affecting Human Evolution?

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JP Rushton

Richard Lynn

L:inda Gottfredson

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1100 words

Our brains are the most metabolically demanding organ we have, sapping 5-600 kcal per day (25 percent of our daily energy needs). Due to how cost-efficient the brain is, it only would have evolved if it gave us a bigger fitness advantage (which it obviously did). In the news a couple of days ago, it broke that C-sections may be affecting our evolution. But in all of the articles I read about it I didn’t see any one of them talking about how C-sections may affect human evolution in America between race. Clearly, if  C-sections are having this effect on the country as a whole, there must be racial differences as well. Could this have an effect on brain size between race in America?

C-sections have increased in frequency since 1996. Clearly, if there is any selection it’s for more narrow-hipped women and bigger-brained babies. The regular use of C-sections has led to an evolutionary increase of fetopelvic disproportion rates by 10 to 20%. (Mitteroecker et al, 2016) Fetopelvic disproportion is the inability of a babe’s head to pass through the mother’s birth canal. This is because the head—and along with it the brain—is too big, leading to emergency C-sections. Mitteroecker et al (2016) also say (which slightly amused me):

Mitteroecker et al (2016) also say (which slightly amused me):

Neonatal size and maternal pelvic dimensions influence fitness (i.e., reproductive success) of the newborn and the mother in multiple ways. Undoubtedly, relative brain size had increased during human evolution in response to directional selection. Recently, it has also been suggested that the large human brain may be the result of runaway selection for the childcare of infants that are born prematurely because of their large brain (12). It is unclear whether any of this selection still persists after the slight decrease of brain size in the late Pleistocene. However, birth weight, which correlates with brain size at birth, is strongly positively associated with infant survival rate (13) and has also been reported to correlate negatively with the risk of multiple diseases (14). Reducing neonatal brain size by shortening gestation length seems to be equally disadvantageous: Delivery before term clearly increases the likelihood of impaired cognitive function in later life (15, 16).

Brain size is decreasing. Associate professor of anthropology at the University of Wisconsin John Hawks also states in his blog post, Selection for smaller brains in Holocene human evolution, where he says (contrary to Pumpkin Person’s assertion) that human brain size has gotten smaller in the past 10,000 years:

The available skeletal samples show a reduction in endocranial volume or vault dimensions in Europe, southern Africa, China, and Australia during the Holocene. This reduction cannot be explained as an allometric consequence of reductions of body mass or stature in these populations. The large population numbers in these Holocene populations, particularly in post-agricultural Europe and China, rule out genetic drift as an explanation for smaller endocranial volume. This is likely to be true of African and Australian populations also, although the demographic information is less secure. Therefore, smaller endocranial volume was correlated with higher fitness during the recent evolution of these populations. Several hypotheses may explain the reduction of brain size in Holocene populations, and further work will be necessary to uncover the developmental and functional consequences of smaller brains.

The reduction in brain size began around 28 kya and accelerated around 10 kya after the dawn of agriculture. The planet getting warmer also played a part in the decrease in brain size, which also allowed for the beginning of agriculture. Anyway, I’m sidetracking, I will return to this point in the future.

Large brains were also selected for since we needed to care for helpless babies. Natural selection for large brains led to more premature births which itself selected for even larger brains.

One-hundred years ago, a narrow-hipped mother who was pregnant with a big-headed baby would have died. Narrow-hipped women with big-headed babies can now survive, transmitting genes for both big brains and narrower pelvises. This is natural selection currently at work as we speak.

One thing that I obviously didn’t see in any article I’ve read on this matter is how will this affect racial differences in brain size? Which race has the most C-sections and will that select for bigger heads and smaller pelvises in that population?

Black women are substantially more likely to deliver by C-section than are white women (pg. 4). Though, one reason that C-sections occur is due to obesity. Black women are the most likely to be obese, which is part of the reason why they have more C-sections. If this trend continues, I could see a slight uptick in black brain size, as even smaller hips get selected for in black women, along with an increase in brain size. That’s one reason why Africans have smaller heads and brains than East Asians and Europeans: they have narrower hips which allows for better athleticism. Conversely, Europeans and East Asians have wider hips which allows for bigger-brained children but hampers athletic ability.

While on the topic of race and C-sections, Asian female-European Male couples have higher rates of C-sections. The obvious explanation is that the Asian woman’s pelvis is too narrow to birth bigger babies. In the study, Asian female-white male couples had babies that had a median weight of 8 pounds, while Asian-Asian couples had babies that had a median weight of 7.1 pounds and finally Asian male-white female couples’ babies had a median weight of 7.3 pounds. However, Asian female-white male couples had an increased rate of C-section deliveries, proving that a significant differences exist between sex of the parent (whether the father or mother is Asian or white influences birth weight) which leads to increased C-section rates due to the white father passing clearly influencing the birth weight more, thusly making it difficult for his Asian partner to birth the baby. There are 100 deaths per 100,000 live births per year in the U.S., a rate of .1 percent. Clearly, though the death rate is low, C-sections lead to maternal mortality and since Asian females are more likely to have a C-section when the father is white due to the baby being bigger, the mortality rate is slightly increased when this interracial pairing occurs.

C-sections are causing natural selection, favoring for bigger heads and narrower hips. This helped us, evolutionarily speaking, as human bipedalism is promoted by a narrow pelvis. C-sections could possibly select for bigger-brained African Americans. Though brain size has decreased in the past 10,000 years, our brain size will slightly increase over time due to this selection pressure. Asian women and white male couples have C-sections more often. Pretty good case against race-mixing, if I don’t say so myself.

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16 Comments

  1. I dunno, I wouldn’t put a lot of trust in the Wong et al., finding: the effect is significant but the confidence intervals for the odds ratios are so wide they vary from an OR of 1.3 in some cases (which is a pretty small effect and arguably uninteresting) to 2.6 (which Is very interesting IMO). While they controlled for the probable confounds like maternal age and insurance, it’s also correlational at the end of the day. I know you’d never be able to look at this experimentally, but I defo think a bit more work is needed on this, particularly as you’ve argued the implications could be really quite interesting

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    • RaceRealist says:

      While they controlled for the probable confounds like maternal age and insurance, it’s also correlational at the end of the day.

      Controlling for age takes away any chance that C-sections occured due to age while controlling for insurance makes sure that they all have pretty much the same health-care. It is correlational, but it’s an interesting finding. It does make evolutionary sense. 100 years ago these people would have most likely died. What the researcher said—that C-sections are selecting for narrow-hipped mothers and big-headed babies makes sense from an evolutionary standpoint.

      I defo think a bit more work is needed on this, particularly as you’ve argued the implications could be really quite interesting

      Most definitely. I’d like to see a study done on C-sections and race. I’d love to see if there was a racial breakdown in this study but it was probably 99 percent white women. I believe there will be selection for bigger crania in African Americans due to this. Though black women are the most likely women to be obese and that is a cause for C-sections as well.

      Black women have narrower hips than Asian and white women. This is one reason why blacks have smaller heads. So I believe there will be selection for slightly smaller heads, and along with it brains, in African Americans in the bear future. I doubt the effect size would be great enough to see any dent in IQ tests, however.

      Mitteroecker et al. (2016) also say:

      Based on this model, we predict that the regular use of Caesarean sections throughout the last decades has led to an evolutionary increase of fetopelvic disproportion rates by 10 to 20 %.

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  2. Afrosapiens says:

    What you say about pelvic size is not true, Asian women have smaller pelvises than whites too.

    https://anthropology.net/2008/10/06/higher-rates-of-c-section-deliveries-for-asian-mothers-white-fathers/

    http://med.stanford.edu/news/all-news/2008/10/asian-white-couples-face-distinct-pregnancy-risks-stanfordpackard-study-finds.html

    Or on another topic:

    http://rstb.royalsocietypublishing.org/content/370/1663/20140063

    But I didn’t come for this. In case someone wondered where I’ve been, Pumpkin Person is now blocking my comments. So I don’t know if it’s male or female but one thing I know for sure is PP has no dick in its pants.

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    • RaceRealist says:

      Looking at only hip size, blacks are more narrow than Whites who are more entries than Asians. Pelvic size is a different story however. And as you can see, the birth rate is directly influenced by the race of the father, which I found very interesting.

      But I didn’t come for this. In case someone wondered where I’ve been, Pumpkin Person is now blocking my comments. So I don’t know if it’s male or female but one thing I know for sure is PP has no dick in its pants.

      He does that to me a lot when I keep bringing something up. Like when I would continuously bring up evolutionary progress he’d throw me in the dungeon for a bit and not moderate my comment out of the graveyard. I assume he does that when his feelings get hurt. I saw how you got his jinmies in a twist. Funny stuff. He’s pretty emotional.

      And do you believe what he said about the people from that show shooting him an email? It seems to me like PP tells high tales and embellishes the truth a lot. He is always calling himself a “celebrity”.

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    • Afrosapiens says:

      “Pelvic size is a different story however. And as you can see, the birth rate is directly influenced by the race of the father, which I found very interesting.”

      I believe one of the link says Asian-Asian couples are at higher risk than white male – Asian woman. Hips width is not what matters, what matters is the size of the birth canal.

      “And do you believe what he said about the people from that show shooting him an email? It seems to me like PP tells high tales and embellishes the truth a lot. He is always calling himself a “celebrity”.”

      No I don’t believe a bit of his stories. If Hollywood really sat at his feet, he wouldn’t get mad at an anonymous French lawyer. I think I’ve said some painful truths about him but he definitely overreacted.

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    • RaceRealist says:

      I believe one of the link says Asian-Asian couples are at higher risk than white male – Asian woman. Hips width is not what matters, what matters is the size of the birth canal.

      And as you can see from the birth weights of the different babies, the race of the father influenced the birth weight. That’s interesting. They cannot birth bigger babies, and as seen, white males who have babies with Asian females have babies that weigh almost 1 more pound on average than Asian-Asian couples.

      No I don’t believe a bit of his stories. If Hollywood really sat at his feet, he wouldn’t get mad at an anonymous French lawyer. I think I’ve said some painful truths about him but he definitely overreacted.

      I find that he embellishes the truth a lot. I roll my eyes at some of the things he writes because I know they’re either highly inflated or never happened and just fluff. He definitely did overreact. I’m thinking he’s a woman due to how emotional he gets at times, but it could be due to having low testosterone and high estrogen. You can tell you triggered him when your comments sit in moderation.

      You’ve definitely touched a nerve. Lol.

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    • Afrosapiens says:

      “They cannot birth bigger babies,”

      It’s a little extreme to say they can’t, they have more difficulty. Rushton claimed Asians evolved to deliver heavier, bigger brained babies.

      “I find that he embellishes the truth a lot.”

      And he doesn’t seem to understand the limit to which his readers can be gullible. This guy has issues, he didn’t notice that there were a few normal persons among his mostly deranged audience.

      “You’ve definitely touched a nerve. Lol. ”

      Yes and he must feel so glorious with moronic marsha counting points and me not being able to answer. His reaction, though hysterical, is not feminine because women love endless arguments whereas me prefer to end disputes quickly and brutally. But real men like to do things less cowardly.

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    • RaceRealist says:

      It’s a little extreme to say they can’t, they have more difficulty. Rushton claimed Asians evolved to deliver heavier, bigger brained babies.

      On average, of course. As you can see from the cited study, the race of the father affects the weight of the baby when it’s born. Asian-Asian couples’ babies weigh on average 7.1 pounds compared to the Asian-white couples 8 pounds. That’s a big difference, which shows also shows that the weight of the babe is influenced by the father in the context of this study.

      And he doesn’t seem to understand the limit to which his readers can be gullible. This guy has issues, he didn’t notice that there were a few normal persons among his mostly deranged audience.

      You can tell by the way they’re written. Anything is possible though, but I highly doubt it happened.

      Yes and he must feel so glorious with moronic marsha counting points and me not being able to answer. His reaction, though hysterical, is not feminine because women love endless arguments whereas me prefer to end disputes quickly and brutally. But real men like to do things less cowardly.

      I enjoy ongoing arguments. I always learn a lot. He does enjoy arguing a lot.

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    • Afrosapiens says:

      “which shows also shows that the weight of the babe is influenced by the father in the context of this study.”

      Probably, but it contradicts Rushton’s law that would have Asian women having less difficulty delivering half white babies who are supposed to be r selected small and tiny brained children. Anyway, I’ve always known Rushton’s theories and HBD are garbage either based on inaccurate or misinterpreted data. So it makes little difference to me.

      “You can tell by the way they’re written.”

      Yes there are some guys with compulsive, obsessions (Zion, Anglo proles, Magic Negroes…) Others that are just dumb/insane. It’s always reflected in their writing style.

      “Anything is possible though, but I highly doubt it happened.”

      Believing to be a celebrity is high level lunacy, even real celebs get uncomfortable with the hype they get and try to keep in touch with reality.

      “I enjoy ongoing arguments. I always learn a lot. He does enjoy arguing a lot.”

      Me too, but only when it’s about confronting knowledge and ideas. The conversation that drove him crazy dealt more with personal attacks that I started, things like that never last long between two men, the most threatening one quickly owns the most moderate. Women can throw ad hominem attacks at each other for hours without any sign of fatigue. That’s why PP’s reaction makes me think he’s a man who got pissed off and brutally used his power to ban me.

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  3. Afrosapiens says:

    I checked the youtube channel of his facts of life videos an none appears to be an official account. So either PP is making up stuff or there is someone making fun of him behind one of those accounts.

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    • RaceRealist says:

      I doubt that actually happened. He seems to be very narcissistic in the way he writes about himself. Of course if he provides prove I’ll retract my statement but I doubt it.

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    • Afrosapiens says:

      Well, he said he’s gonna receive some gifts so he could post some selfies with them. Thus he will reveal his identity (Which is a good start for a celebrity, lol) and prove he was telling the truth. But I doubt this will happen. And it’s rather strange for someone who claims to be part of the upper class to be in adoration with TV and horror movies, that’s not the upper class in which I live.

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  4. Afrosapiens says:

    Hi, what do you think about that ?

    “Many traits in many species have evolved through sexual selection specifically to function as ‘fitness indicators’ that reveal good genes and good health. Sexually selected fitness indicators typically show (1) higher coefficients of phenotypic and genetic variation than survival traits, (2) at least moderate genetic heritabilities and (3) positive correlations with many aspects of an animal’s general condition, including body size, body symmetry, parasite resistance, longevity and freedom from deleterious mutations.
    These diagnostic criteria also appear to describe human intelligence (the game factor). This paper argues that during human evolution, mate choice by both sexes focused increasingly on intelligence as a major heritable component of biological fitness. Many human-specific behaviours (such as conversation, music production, artistic ability and humour) may have evolved principally to advertise intelligence eduring courtship. Though these mental adaptations may be modular at the level of psychological functioning, their efficiencies may be tightly intercorrelated because they still tap into common genetic and neurophysiological variables associated with fitness itself. Although the g factor (like the superordinate factor of fittness itself) probably exists in all animal species, humans evolved an unusually high degree of interest in assessing each other’s intelligence during courtship and other social interactions and, consequently, a unique suite of highly g-loaded mental adaptations for advertising their intelligence to one another through linguistic and cultural interaction. This paper includes nine novel, testable predictions about human intelligence derived from sexual selection theory.”

    http://download.bioon.com.cn/view/upload/201307/31134632_2716.pdf#page=269

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    • RaceRealist says:

      This paper argues that during human evolution, mate choice by both sexes focused increasingly on intelligence as a major heritable component of biological fitness.

      I completely agree. Peter Frost has a lot of work on sexual selection. He says the same things. Richard Fuerle, author of Erectus Walks Amongst Us says that Eurasian men were selected for intelligence while women were selected for beauty. He says on Africa it was the reverse, with women farming and gathering while African men were selected for physical attractiveness.

      I’ll read this paper tonight and get back to you, very interesting, confirming what I’ve thought about sexual selection and intelligence as well. Sexual selection is a form of natural selection.

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    • Afrosapiens says:

      Yes, read it, you’ll find out more interesting information than your pseudoscientific references.

      According to this theory, what PP calls schizophrenic traits (coolness) or Rushton r selected traits are manifestations of sexually sexually selected intelligence and fitness.

      According to this paper, sexual dimorphism can’t emerge because parents pass on their genes to boys and girls in the exact same manner (not mentioning the Y chromosome that has very few genes).

      Moreover, what you say about Africans is wrong, African men work a lot, in more cognitively demanding activities such as hunting, home building, crafts, large scale trade or strength demanding farming activities. It is true that women do most of the simple farming tasks but that also holds in Eurasian traditional farming societies. And African men can’t be selected for attractiveness because African societies are patriarchal, men chose women and not the other way around.

      Anyway, read the paper, it’s interesting. And I’ll be interested by how you’ll interpret it. I doubt it describes sexual selection for intelligence in the way you agree with it.

      “Sexual selection is a form of natural selection.”

      It is a force of evolution that is distinct from natural selection. This paper argues that human intelligence is too evolutionary costly and futile to be the product of natural selection. If it were only about survival, the intelligence of chimps or Japanese macaques would have been just enough and at a lower cost. Human beings became intelligent by mating with entertaining and talented humans.

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    • Afrosapiens says:

      On sex differences in human mate preferences:

      http://philipperushton.net/wp-content/uploads/2015/02/iq-race-sex-gender-survey-mate-buss-nyborg-rushton-buss-behavioral-brain-sciences-19891.pdf

      As a whole, Africans are more likely to give importance to mate financial prospects, ambition and industriousness than Europeans, East Asians resemble Africans more. That might be related to the fact that they have more traditional cultures. In each group, females select more on financial prospects, ambition and industriousness than males.

      African men prefer significantly younger women than East Asians and Europeans, and African women prefer slightly older men than Eurasians. That’s easily explained by polygyny in which male-female age differences are always significant. This differential might be interpreted by a selection for fertility in females and social status in women.

      Africans are more attracted to good looks than East Asians and Europeans, Males in each group are more attracted than women. Might be seen as a sign of selection for health, fertility and global fitness. Women are more sensitive to social status, which probably reduces their interest for good looks.

      East Asians value chastity the most, Europeans the least, Africans are in between but somewhat closer to Europeans. Men value chastity more than women who, relative to other traits, literally don’t give a fuck (except for the Chinese). I think men’s valuation of chastity has to do with ascertaining paternity, whereas Female low valuation only reflects expectations of paternal investment in offspring that can be substituted by other forms of social support.

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