On a recent episode of the Dear Hank and John podcast (in which two brothers give “dubious advice”, I recommend it!) a listener sent in a question about why human infants were so useless. And even though both of them have children of their own, they didn’t really know what the answer was so they gave it their best shot: (paraphrasing here) because of bipedalism, women’s hips are too narrow and the baby needs to come out prematurely otherwise they won’t fit.
If you’ve read the earlier parts in this series debunking the Obstetrical Dilemma, you can imagine my epic head shaking and eye-rolling. I had already had this post waiting in the wings but I decided to rework the intro and title when I realized that lay people who have never heard the phrase “obstetrical dilemma” will forward it without even being aware of it. So, why are newborn humans useless?
Anyone who has cared for a newborn as been there. That moment when you feel like you have tried everything to soothe your crying baby and you just want to sit down and cry yourself. But what if there was some magic trick that would calm your baby and brighten your own mood? According to science there just might be some magic in taking a walk with your baby– but you’ll need to carry them for the full benefit. Continue reading
Humans, like the other Great Apes, are physiologically riders; breast milk composition is not suited to parking infants for long periods between feeding (Ross). For this reason among many others, our species has had to carry our babies with us wherever we go. Unfortunately, humans find carrying infants more difficult than our evolutionary cousins for three reasons: lack non-grasping feet and body hair, physically helpless infants and, most importantly for this post, the relative size of our infants.
Non-human apes in the taxonomic family Hominidae (literally means “Great Ape” and makes me think of Charlotte’s Web’s “Some Pig” but I digress) have smaller, more precocious babies than humans. Adult gorillas, for example, are significantly larger than adult humans, yet their newborns are about half the size of human newborns. Chimpanzees, which are our closest extant evolutionary relative and have a similar adult body weight to us, give birth to newborns that are around 3% of their adult size, while humans have newborns that are around 6% of adult size (DeSilva). At what point since our common ancestor with chimpanzees, did hominins start having bigger babies? Continue reading
Many moons ago at a family gathering, a relative was complaining about her baby’s fussing, “He won’t let me put him down and he’s so @#%!ing heavy!” I offered to get one of my baby carriers out of my car and she refused, claiming that he was too heavy to be carried all the time. I tried to say that “the weight seems to disappear in a carrier because of the distribution…” but she wasn’t listening. Fully glazed expression as she was strapping him into a 20 lbs car seat, in order to swing it from arm to arm, for the. next. four. hours.
But back to that bit about infant carriers making baby’s weight seem to disappear. Those of us babywearing nerds can give a good schpeel about how (ergonomic) infant carriers distribute the weight through the pelvis instead of pulling on the shoulders. But is there a way to scientifically quantify how an infant carrier reduces the energetic drain of carrying? Why yes, yes there is– by measuring the differences in calorie expenditure between different ways of carrying.
Have you ever wondered why some animals create a nest or den for their offspring, while others carry their babies everywhere they go? These represent two reproductive strategies, or ways of producing and caring for offspring that survive to sexual maturity, called parking and riding respectively. Continue reading