Evolution is not an excuse

One of the more pervasive errors of thought among the AP/NPers that I see is the assumption that since humans evolved in a certain way, the solution produced by evolutionary forces therefore must be perfect in every humanly possible situation. “Babies have evolved to cosleep”, Tells us James Mckenna, the anthropologist whose studies on sleep physiology are used incorrectly as “proof” cosleeping prevents SIDS. “Human milk is perfect for babies, honed by thousands of years of evolution”, so say the lactofanatics.

While these statements are, in principle, correct, they are not the whole truth of the matter.

The evolutionary principle of natural selection dictates that the fittest phenotype of a given species of living being, i.e, that which provides the greatest survival advantage in the particular environment the species exists in will prevail, and its descendants will proliferate while other species diminish and may eventually become extinct. It does not, however, mean the fittest option will be Practically Perfect in Every Way, or even ideally suited to the environment – merely the best suited among all the other options and the one most conducive to the species’ survival and reproduction in that particular situation.

The classic example given is that of a population of moths, some black, some white. If the surrounding environment provides a better camouflage for the black moths, the white ones will be easier for predators to spot and their numbers will diminish, perhaps to extinction. It doesn’t matter if the white moths are healthier and stronger, or even if the black moths had a recessive genetic mutation which made 1/4 of them sterile – the black moths would still have the survival advantage in this situation. Evolution often involves payoffs. A commonly-used example of this phenomenon in humans of African descent being how people with sickle cell trait, who have a single copy of a certain gene for one protein in the hemoglobin molecule, have greater immunity against malaria than people without this trait; however, those unlucky enough to be born with two copies of this gene have sickle cell anemia and are destined to a shortened, painful life.

We must also remember that evolutionary advantage is environment-specific. Continuing with the moth example, if the moths’ environment were to suddenly change so that now the white moths were better camouflaged, the black moths would now be preferentially snapped up by predators and the white moths’ population would be considered the fittest. What was previously considered an advantage may now become a distinct disadvantage.

Let’s look at these evolutionary principles in the context of ‘natural’ practices such as cosleeping (in the sense of bedsharing) and breastfeeding.

For hundreds of thousands of years, Homo Sapiens lived as hunter-gatherers, originating in the warm regions of Africa. They slept out in the open, on the ground, with little covering their bodies, and their babies close by. While a very small percentage of babies may have died as a result of SIDS or suffocation, the danger of babies being carried off in the night by wild animals was several orders of magnitude greater. Hence, human society’s very survival depended upon keeping children physically close at all times, especially at night. The minimal payoff of having some babies die as a result of SIDS or overlaying was a paltry evolutionary price to pay. It may even be that Mckenna’s physiological findings – that cosleeping infants and mothers have synchronized arousals and breathing patterns – conferred greater survival among cosleeping babies than those who didn’t develop those characteristics (though I doubt having more episodes of central sleep apnea did much for our survival as a species).

However, our environment today is radically different: most of us live in well-protected houses, many live in climates colder than the African Savanna and use soft beds and heavy covers. The chance of a baby dying of SIDS/SUDI is now greater than being carried off by wolves. Furthermore, the evolution of human medicine and ethics means we no longer tolerate babies dying for preventable reasons. What once was the fittest solution may no longer be the case.

So to say that “babies evolved to cosleep” completely disregards that this evolution took place under very different conditions, and possibly allowing for less than 100% survival. Which, evolutionarily speaking, is OK – if one wishes to anthropomorphize evolution, one could say it isn’t looking out for the survival of any specific baby. That’s not good enough for modern medicine or most parents, though. Thus, while the claim that “human babies evolved to cosleep” is technically correct, it’s also irrelevant in today’s context.

How about breastfeeding? Well, it’s certainly highly-evolved to be the best nutrition for babies, and as of 2008, certainly, no formula can match it. But does that mean it’s perfect for babies – i.e, does it provide everything all babies born today need for optimum growth?

The answer is no. Breastmilk has not evolved to supply the needs of very premature babies, for example, as until no more than a couple of decades ago, these babies would not have survived long out of the womb. Compared to such babies’ increased nutritional needs, breastmilk is deficient in fat and certain vitamins and minerals. Don’t get me wrong – breastmilk still has a huge advantage in such babies over any formula, but human milk fortifier still needs to be added for optimal growth and development of these babies.

Breastmilk is not perfect for term babies, either: it is deficient in vitamins K and D and iron, which makes breastfed babies more vulnerable to deficiencies of these. While the overwhelming majority of breastfed babies do not develop dangerously low levels of vitamin K, some do; vitamin K administration at birth saves these babies from bleeding to death. Vitamin D supplementation is something that even I admittedly neglected somewhat as a mother*; however, a recent study from Boston demonstrated that regardless of pigmentation, almost 1 in 8 (!) babies and toddlers had vitamin D deficiency; of those, a significant minority had evidence of bone demineralization and even rickets. The main culprit? lack of external oral vitamin D supplementation – via drops in breastfeeding babies, or cow’s milk in toddlers.

But people who are caught up in the “breastmilk is the perfect nutrition” dogma are often too ideologically blinded to see these realities. Witness the reluctance in AP/NP circles to give vitamin K at birth, the mental gyrations lactofanatics go through to avoid giving vitamin D supplements…and if you want to know what some of them think about human milk fortifier for preemies, you need only to search for the term at mothering.com’s messageboards.

I’ll repeat what I’ve said before: Nature/evolution is a cruel goddess. She/it is NOT looking out for YOUR baby’s welfare. To invoke these elements as the final rationale for adopting or rejecting a particular practice will inevitably lead to a “natural” result: illness and death for some babies. And that is something most rational parents in the 21st century find intolerable.

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*Given that I live in a much warmer, sunnier part of the world than Boston, it may be that my not being completely on top of vitamin D administration was of lesser consequence than in the study described. It still – I admit – wasn’t an awfully smart thing to do, even though, to the best of my knowledge, my kids are fine.

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22 Responses

  1. Excellent post. I did the Vitamin K shot at birth (with much trepidation, as I was heavily infested in the ‘natural’ model at the time) but did not do the Vitamin D drops. My pedi was not too worried about the Vitamin D as we live in a sunny area in the south of the U.S., but I do not think the Boston study was available at that time; perhaps her recommendations are different now.

  2. This particular study is fresh off the press (June 2008), but if you look at its first paragraph, you’ll see there are reports of vitamin D deficiency and even clinical rickets from sunny areas of the US and the world in general. The recommendation to supplement with Vit D wasn’t made to enrich Big Pharma (there’s no patent on vitamin D, so it could hardly be a huge moneymaker, anyway) – it’s an honest-to-goodness attempt to prevent deficiencies.

  3. Hey, I have a question about supplements at birth that your excellent post reminded me of. Considering that the baby’s gut is sterile, wouldn’t the oral vitamin K, vitamin D supplements, etc cause more problems than good with mothers and infants who are advised to limit mixed feedings to prevent introduction of foreign substances? I’m talking about like mothers who can’t formula feed but have HIV, I’ve read studies saying mixed feedings increase transmission rates and was curious how that would weigh against the benefits of supplements or fortifiers.

    Also, the above drives me CRAZY. As a biologist with a specialty in ecology and evolution, I understand how it works– and that often evolution gives us stuff we don’t want or need just because it doesn’t affect our ability to breed.

  4. Well, an infant’s gut doesn’t stay sterile for very long, and we don’t start vitamin D supplements until babies are a month old here. I honestly don’t know if the 2 measly drops of oral vitamin D (you can preferably give vit K by injection like most mainstream people do) would have that serious an effect – most of the damage done to the gut by formula is mainly via the foreign milk proteins. This would also only be relevant if a child with an HIV-pos mother were breastfed to any degree, but in the western world, the recommendation is to fully FF from birth.

  5. Thanks. I was referring to women who cannot afford formula, bottles, or water purification and live in countries where there isn’t a system set up to help them pay for the expense.

  6. Breastmilk is deficient in Vitamin D because human infants will have minimal, safe exposure to natural sunlight unless illness or cultural imperatives keep them inside or constantly covered. Drops are an inferior substitute inviting dosage errors.

  7. Em: As we see in practice (see studies referenced), even in sunny countries, vitamin D deficiency is not unheard of, especially since exposure to sunlight has the same “risk of dosing errors” you state is relevant to vitamin D, causing sunburn and future risk of melanoma. And you have no basis to declare that vitamin D supplements are in any way inferior – they do the job, are biologically identical to the vitamin D synthesized by the infant’s body (or rather, the active form of Vitamin D is transformed in the body from the supplements given), and the amounts normally given are far,far below any amount that would cause toxicity – so there’s a huge margin for error here. A baby/toddler accidentally getting into the medicine closet and drinking the whole bottle notwithstanding – but that could happen with just about anything.

  8. Paragraph 9: The author neglects the fact, that human children are born very early (in terms of development) so that they can fit through the birth canal (giving up development time in womb to have a larger brain). There for, children need more direct contact (especially during the first 3 months of life) for them to properly develop (the contact and “cuddling” that they would have gotten in the womb).

    Paragraph 11: Actually, breast milk is specially designed (or is different) for each baby. That means if a child is born early mom’s milk will adapt to those specifications of the child. Also, breast milk is NOT deficient in Any vitamin or mineral. That is a common misconception. Yes, infant formula may contain more of a vitamin or mineral (all laboratory produced) but far less of it is used by the child when we compare the absorbshun of the same vitamins and minerals (naturally produced) in beast milk. Therefore, breast milk doesn’t need to have as much of something because almost 100% of it can be used by the body.

    Paragraph 12: The author says in a study, 1 in 8 babies and toddles have a vitamin D deficiency. May I point out that (US statistics) 70.9% (2003) of women “try” (that included even one “nursing session) to breast feed but by 6 months the rate is only 32.6% (and that includes babies that are receiving both BM and F along with BM exclusive babies). The breast feeding rate is even lower at 12 months, 17.2 (also including EBF and supplement babies). Note that the WHO recommendation is 2 years! There for, it can be easily said that a lack of vitamin D in breast milk is NOT the problem!

    I think that the author needs to do some more research before he/ she goes making statements like this!

  9. Thank you for the entertainment, Wendy. You’ve managed to cram lots of AP/NP myths and non sequiturs in there. Let’s address them one by one, shall we?

    Paragraph 9: The author neglects the fact, that human children are born very early (in terms of development) so that they can fit through the birth canal (giving up development time in womb to have a larger brain). There for, children need more direct contact (especially during the first 3 months of life) for them to properly develop (the contact and “cuddling” that they would have gotten in the womb).

    That’s fine, but not really germane to the paragraph. It doesn’t mean babies need to be attached to you 24/7, or that you must sleep with them in bed. Also, in practice, babies grow and develop very well in modern homes even when not latched on all night. (Kangaroo care for preemies is also not 24/7, and the benefits on growth and development in preterm babies have not yet, to the best of my knowledge, been shown in term infants. Even in kangaroo care you can put the baby in a bed/incubator for sleep when you sleep, though).

    Paragraph 11: Actually, breast milk is specially designed (or is different) for each baby. That means if a child is born early mom’s milk will adapt to those specifications of the child. Also, breast milk is NOT deficient in Any vitamin or mineral. That is a common misconception. Yes, infant formula may contain more of a vitamin or mineral (all laboratory produced) but far less of it is used by the child when we compare the absorbshun of the same vitamins and minerals (naturally produced) in beast milk. Therefore, breast milk doesn’t need to have as much of something because almost 100% of it can be used by the body.

    Ah, the cute lactofanatic myth: “breastmilk is tailor-made for each baby”. I hate to break it to you, but Mom’s body has no way of knowing what specific nutrients the baby needs at any given time. It’s quite true that breastmilk nutrient content is adapted to the baby’s age and changes over time, but that doesn’t mean mother’s milk can be produced to respond to your individual baby’s every need, nor that even term babies never need nutrients above and beyond what breastmilk can provide.

    Either way, as I pointed out in the post – a 28-weeker in nature would most probably be dead of respiratory failure until about 25 years ago; hence there was no evolutionary need to provide developmentally-specific nutrition for small preemies until then. Human milk with added fortifier – again, in practice – has distinct advantages over plain milk provided by mother: it clearly makes them grow better and be better nourished. See here and here.

    Another little myth that – your body has no idea whether the vitamins and minerals you receive were synthesized by your body or in a lab.

    Paragraph 12: The author says in a study, 1 in 8 babies and toddles have a vitamin D deficiency. May I point out that (US statistics) 70.9% (2003) of women “try” (that included even one “nursing session) to breast feed but by 6 months the rate is only 32.6% (and that includes babies that are receiving both BM and F along with BM exclusive babies). The breast feeding rate is even lower at 12 months, 17.2 (also including EBF and supplement babies). Note that the WHO recommendation is 2 years! There for, it can be easily said that a lack of vitamin D in breast milk is NOT the problem!

    Without getting into whether the WHO recommendation is as important to babies in the developed world (and if you think the WHO is equally brilliant when they advocate vaccines), the stats you provided about exclusive and non-exclusive breastfeeding have nothing to do with the fact that again, practically speaking, vitamin deficiency and even rickets were more prevalent when babies breastfed and didn’t receive vitamin D supplementation. As I pointed out in previous comments, this isn’t a new finding. What would be relevant is if you found me information showing that infants who are exclusively breastfeeding, or who breastfeed for extended periods, are somehow protected from vitamin D deficiency in way that mere mortals aren’t. But having looked at the studies, I can confidently state you won’t find any such evidence as it’s simply not true.

    I think that the author needs to do some more research before he/ she goes making statements like this!

    I think the author of the above comment needs to stop believing every piece of nonsense she reads on BF advocacy websites, learn how to read actual medical studies and get her own information…

  10. The author needs more credible evidence to back up her bullshit claims.

  11. estherar: in the western world, the recommendation is to fully FF from birth.

    You’re JOKING, right? The recommendation, WORLDWIDE is exclusive breastfeeding for at least 6 months, and then to continue breastfeeding until a minimum of 2 years, preferably allowing the child to self wean.

  12. Jodie – if you want to refute my claims and show how they’re bullshit, you’re welcome to try. I don’t think you’ll have much luck using reliable sources, however, since what I said is all true.

    Anonymous – the discussion above is regarding babies born to HIV(+) women. The recommendation to FF these babies from birth where formula and clean water are plentiful comes from the very same WHO you’re quoting:

    When replacement feeding is acceptable, feasible, affordable, sustainable and safe, avoidance of all breastfeeding by HIV-infected mothers is recommended.

    And tell me – do you also agree that the WHO, which made the recommendations to breastfeed exclusively for 6 months and in general for 2 years, is also correct when it advocates WORLDWIDE vaccination?

  13. Em, Studies have shown that it is impossible to manufacture sufficient Vitamin D from sunlight at high latitudes (45-50N and further north) for up to 6 months a year. One page I read–an LLL leaders handout no less!–said it was possible even at 40. Rickets is becoming a problem again in the UK and Canada (exacerbated in certain groups that expose very little skin).

    The Inuit do traditionally eat large quantities of oily fish, which is high in Vitamin D. (Before you ask how people lived at high latitudes prior to artificially synthesized Vitamin D.)

    Esther, it’s always amused me when the NFL types quote the WHO on breastfeeding, but they’re WRONG! WRONG! WRONG! about vaccination.

  14. LLL’s info is not usually a source I recommend – they’re too fanatical to give out accurate information on certain topics. Like the craven and confusing statement they put out in 2005 regarding HIV and breastfeeding. As if most women with access to LLL materials (especially online!) don’t also have ready supplies of clean water and formula!

  15. I’m not necessarily recommending LLL as an unbiased source; just that if even LLL is coming out and saying that sunlight isn’t enough, you might want to accept that it’s true. They did have citations, but I can’t find the page now.

  16. I see. I didn’t read your previous post correctly, sorry.

    Assuming the LLL is correct, keep in mind that NYC and Madrid are at 40 degrees of latitude, an a lot of people live north of those cities…

  17. The obesity epidemic is a good illustration of the fallacy of believing that traits that have adapted to be beneficial in one environment will automatically be beneficial in all environments.

    Back in the Stone Age, when food was scarce and we lived a very active lifestyle that required a lot of energy, we evolved to eat as much sugary and/or fatty foods as we could get our hands on. In that environment, it was a beneficial trait; it ensured that we didn’t let valuable calories pass us by, that we took every opportunity to get enough fuel to keep us going. Of course, these days we live in a different environment, where food of all kinds is plentiful and our lifestyles require far less energy. In this environment, our love for high-calorie foods is having terrible effects on the health of the population. A trait that was once vital to our survival has now become positively harmful, just because we’re now in a different environment.

  18. There is a nice study looking at supplementing mom’s vitamin D intake improving vitamin D stores in the breastfeeding infant. Certainly if the mom is deficient, her milk will be too (and so will the neonate’s liver stores).
    Whether you’re in a “sunny” clime or not, we spend so little time outdoors (more in our house, our car, our workplace) and what time we do spend we’ve been told that we have to slather up with sunscreen to prevent skin cancer– little wonder that we’re not making as much vitamin D as we should.
    I live at 40 degrees, and 10 minutes a day a few times a week is all I need… I’m not taking my newborn sunbathing but I wasn’t planning to put them in a foil pouch every time I go outside either.

  19. Very late to the conversation, but wanted to say this is one of the best explanations I’ve ever read of evolution as it impacts childbirth and childcare. Another point to make is that you can have competing evolutionary pressures–witness Vitamin D deficiency vs. melanoma. You are absolutely right when you say Mother Nature is a cruel mistress.

  20. “So to say that “babies evolved to cosleep” completely disregards that this evolution took place under very different conditions”

    You are assuming two things,
    1) enough time as passed to change a trait and
    2) it would be changed at all.

    Evolution is a slow proccess. It does not matter that the conditions are different today (in the western world that is) because not enough time as passed to change such a basic instinct if it was to be changed at all that is.

    It is not true that because an enviroment is different than what it was that a current unnecessary trait will be replaced.
    Animals retain many traits that are currently unneeded often because there is no cost advantage to altering them.

    Co-sleeping is not an expensive trait so is unlikely to alter any time soon (just like the trait of babies to try and grab with their feet, another meaningless but cost-free trait that we retain).

    • Co-sleeping is not an animal instinct nor an inalterable physical trait. It’s a behavior that humans can choose either to do or not to do. Whether there is an evolutionary advantage to a certain behavior depends upon human environment, which has changed dramatically in a short time.

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