Pregnancy and Evolution

This one is for the ladies, because the men probably won’t be able to sympathize. At least not as much as we should.

Ever wonder why pregnant women don’t just topple over and break their noses? Especially the ones that look like they mated with a bull elephant, and are carrying twins? How do they possibly carry all the extra weight around in that one, basketball shaped pouch between their breasts and their knees, without falling over? I know that I couldn’t do it. It’s hard enough carrying what I have.

Turns out I can’t. I don’t have the backbone for the job, but women do, because of evolution.

Our ancestors, way back when, tended to walk with the assistance of all four limbs, much like monkeys do now, so the females could support the extra weight with their hands. When we began to walk upright, however, the normal effects of gravity on the mass of the fetus approximately mid torso would have been enough to drive her forward, or, when compensating for it by leaning backward, exert unrelenting stress on the back muscles.

So evolution steps in and changes things. Women developed a change to the shape and function of the lower vertebrae that allowed the stress placed on the back by shifting her revised center of mass backward, so as to be more efficiently handled by the lower spine.

By comparing skeletal samples of men and women between the ages of 20 and 40, the researchers pinpointed the differences that allowed women to perform this balancing act. Women had three wedged vertebrae whereas men had only two, allowing the women to create a more extreme curve. In addition, the women’s facet joints, which connect the vertebrae and prevent twisting of the spine, were larger relative to their body size and positioned differently to redirect the weight and enhance resistance.

Men don’t have this adaptation, most likely because when we were lean, mean hunter-gatherers, before the invention of beer, and beer bellies, we didn’t need it.

(Click on graphic)

So, my male brethren, the next time you see a woman doing the pregnancy waddle, with that stance peculiar only to the soon-to-give-birth, (you know, belly out, hand on the small of back, shallow breathing) try to appreciate the fact that god evolution has made her better than you.

20 thoughts on “Pregnancy and Evolution

  1. So just how many more generations have to pass and how much more beer do us men types have to get through before we evolve?

  2. SI, I don’t think you understand. GOD made women exactly like they are for a reason. GOD is a really smart dude. He knew the problems his “walking women” were going to have in pregnancy. Why do you think he took Adam’s RIB to design the new creature – woman? Hell, Adam was already having lower back pain and he hadn’t even developed a beer belly (GOD invented beer much later). Anyway, that’s why he didn’t make Eve out of vertebral material.

  3. Just because we’ve got an extra lumbar section doesn’t make it any more comfortable however!

  4. Okay, we’ve evolved to the point that a certain amount of the discomfort of carrying babies is alleviated. And not a moment too soon. So, when will the adaptation that alleviates the intense, indescribable, teeth-grinding pain of the actual birth process evolve? It’s way overdue.

  5. chappy:

    So, when will the adaptation that alleviates the intense, indescribable, teeth-grinding pain of the actual birth process evolve?

    As soon as we men get spine equality, we’ll see if we can put in a word with the Big Guy. Why’d you gals have to go eat from that Tree of Pregnancy, anyway?

  6. Exterminator:
    Why’d you gals have to go eat from that Tree of Pregnancy, anyway?

    Is that how it happened? Guess I should’ve had a banana instead.

  7. My dad always says (right before mom creams him with a pillow) that the dad has the hardest job — waiting. Unfortunately, us big time spear carrying hunter types aren’t well equipped for waiting. Patience is not a male thing (at least not for me, or just about any other male I know (though my wife did get real impatient about month 8 for both kids)). But now we know that, while men are not equipped to wait, women are evolved to carry the kid. So what was she complaining about?

    My wife has often remarked on the amazing survival rate of women through the entire mating process.

    Good post. Shows evolution in action. Cool.

  8. Reminds me of that chair lifting experiment. IIRC, something about bending down at a certain angle and lifting a chair. Only women can do it because their center of gravity is different.

  9. I don’t know about anyone else here, but I think that men have evolved to be able to do a VERY tough job: living with a pregnant woman. I’m so glad I’ll never have to go through that again!

    But then, one hears things…like the wife of a colleague who reminds him every day about her travail. and they are in their seventies. He’s told me that in the long run, he recommended celebacy. Short term frustration, long term rewards. In his case it may be true.

  10. I notice that most of your commentators are fellow God-debunkers who agree with you and say, “Hooray for our side!” Well, sorry to be a party-pooper.
    I suppose you have access to all the intermediate forms that demonstrate this evolutionary process? Are you saying with your cute little cross outs that because you believe it was an evolutionary process that God had nothing to do with it? Well, you are certainly entitled to your opinion but, for the record, I believe God had everything to do with it…evolutionary process or not.

  11. Every party has a pooper…

    Flip it around, Dwight. How exactly did god do it? He just snapped his fingers and changed the bones in a woman, and they’ve been that way ever since? Sorry, that’s no explanation. That’s wishful thinking, with nothing to base it on.

    That’s faith….

  12. Dwight Whitless says: I believe God had everything to do with it.

    And on what evidence do you base that belief?

    Or do you expect that we’ll listen to your foundation-less assertion and suddenly smack ourselves in the head. “Hey, of course. Whitless is right. Why didn’t the scientists think of that?”

  13. Dwight Witstett said: “I suppose you have access to all the intermediate forms that demonstrate this evolutionary process? “

    Dwight, one of the canards which the intelligent design group, as well as the creationist groups, have been using again and again and again ad nauseum is the one about intermediate fossils. Every time paleaontoligists and evolutionary biologists find one of these so-called missing links, the intermediate forms, the ID/creationism community immediately starts yelling, well where are the intermediate forms between the new fossil and the ones preceding and following. Every intermediate form found creates two new gaps. To a rational thinker, this means, ah, we must continue to look (or the change (due to evironmental pressures) happened very quickly, in which case the intermediate intermediate forms may not be found) for more clues. To a theist, every gap in knowledge is filled with the same three words: “god did it.”

    I remember in high school (here I go again) listening to a creationist acquaintance talk about how there were no intermediate forms for whales. Then, in the 1990s, a series of fossils were found in Pakistan (including (if memory serves) pakiocetus (sp?)) which showed step by step how whales went from marsh-dwelling bear/wolf like creatures to sea-living creatures (including a step which, in terms of eco-niche, looked a lot like a polar bear (which is a good example of an intermediate form between land-dwelling and sea-dwelling (and if we don’t fry their environment, in a couple two three million years may well look more like seals or sea lions))). The cretinist (sorry, creationist (must be polite, must be polite, must be polite)) groups immediately abandoned the screams about intermediate forms in whales and went on to knew and better things.

    As far as the fossil evidence for the shifting of the center of gravity in bipedal hominids (and keep in mind, this is a new finding, so hominid anthropologists have not been looking for this change yet), I suspect that it will show up in the australopithecoid fossil record. Keep in mind, we have a reasonably complete skeleton of a female australopithecus in Lucy. Maybe the evidence is there. Maybe not. Maybe Lucy spent a lot of time falling on her face (which her long-term descendents seem to do whenever they bring up this “god did it” canard to preserve their precious world-view (must be polite, must be polite, must be polite)).

  14. Dwight

    I agree with Billy, (and I commend his civility, forced as it may be 😉 ) Extrapolation and burden of proof are the concepts of the day.

    First, there is so much evidence that evolution occurred, with fossils that fill in the gaps being found virtually every day. The nature of fossilization most likely prevents us from ever finding all fossils of all species, but that’s where extrapolation comes in. We can extrapolate the intermediate fossils, and predict what characteristics they will have and where they will be found, if they are found. And you know what? Every time we do find one, it’s exactly where we predicted it would be.

    An example is the whale that Billy refers to. Do you think we just stumbled over some fossil in Pakistan? No, we can extrapolate what time frame the intermediate fossil would be, by figuring out the time frame the fossils on both sides are in. We know where there are good rock formations from that time period. We go to those rock formations and predict that if evolution is correct we will find an intermediate fossil between land animals and whales in those rocks. And that’s what happened, that’s where they were found.

    With regard to the God Hypothesis, the one you espouse, we cannot predict how and where god will strike next, to change a species. We have no evidence, not one shred, that indicates exactly how god does it. We have no place to look, as a result. These IDiots who call themselves Intelligent Design Creationists start from the proposition that God created everything, then work their way backwards in the hope of finding the evidence to support their conclusion. What science do you know of, Dwight, that presumes the conclusion before it even begins to look for evidence?

    Now, when you assert that you believe god did it, then it is up to you to provide the proof to support it. We believe that it’s evolution through natural selection that explains speciation, and there are tons of evidence to support it, and none to refute it. What evidence can you supply for your proposition?


    Which is why it’s best to simply say that science is correct, but you don’t believe it because you have faith in your god. The implication is that evidence doesn’t matter in matters of faith. Evidence is thrown out the window, when you say, as you did, “I believe God had everything to do with it…evolutionary process or not.”

  15. Regarding our recent conversations about whales and missing links:

    Yet another missing link has been found! This new find links whales to quadrupedal land mammals.

    The Wissen et al. report in Nature new fossil material from the Middle Eocene of Kashmir, India. This species is represented by a remarkable set of remains, including cranial and post cranial material. Previous studies using DNA had linked whales to the artiodactyls (even-toed ungulates such as deer, antelope, and bison). However, there is a great deal of uncertainty, and some contradictory evidence, as to where exactly in this group the whales arose.

    The full report can be found by going to (sorry, I forgot how to embed a link).

  16. GOD said “BANG” and it happened. All this evidence as you call it can’t be proven. It changes to often and is all estimates or guesses. I’ll give you that as far as evolution that there are some factors that may be close but the world is to perfect to happen by chance. Faith is a big thing. To believe by FAITH is to truely believe. I can create all kinds of evidence but it doesn’t mean any of it is fact. Prove that man came from monkeys. Don’t show me your theories, show me a half man half monkey. Show me this monkey man. You say you have evidence and christianity doesn’t but the truth is there is no true proof of anything. All you have is what you think happened. Proof is actually having true evidence (half man half ape) not your theory of what your Faith says. You have Faith in humans. But to be human is to error.

  17. You want to see a half man, half monkey? Look in the mirror!

    Thinking again, I guess even a half man would tell the difference between “to” and “too”. Hummmm….

    Would you be satisfied with a 3/4 monkey, 1/4 man?

    (sorry guys, I’m not even a regular poster, but I just couldn’t help my self.. 😉

  18. That’s OK, Brazilian. I wasn’t even going to respond to IbitBB. Anyone that thinks “man came from monkeys” has absolutely no idea what he’s taking about, is so invested in his religious beliefs that he will never change them, and is not interested in any real debate, or of even the possibility of learning something he never knew.

    At least, that’s my experience.

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