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.
*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.