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?
Apes, including humans, are physiologically riders, meaning that they carry their babies with them as opposed to leaving them in nests or dens because their breast milk composition is not suited to leaving their infants alone for long periods of time (Ross, 2001). But unlike humans, apes don’t need a tool to carry their infants in part because they have body hair for their infants to cling to but it’s more complicated than simply having body hair and a baby that can grasp it. Hair strength, density, infant weight, carrying position, adult posture, and even humidity play a part in successful infant carrying without tool use. Continue reading
The phrase “childbearing hips”, besides being extremely cringey in any context, is a misnomer. It’s a byproduct of the kind of thinking that went into the Obstetrical Dilemma: in order to give birth women traded in bipedal efficiency for wider hips. It’s a hypothesis that was and is widely assumed to be true. But you know what they say about making assumptions? … As it turns out, pelvic width has nothing to do with bipedal efficiency, nor is it a constraint for fetal head growth or childbirth. Continue reading
Are you curious about how life evolved on planet Earth? Well, grab a snack and a beverage and settle in for a few billion years. Here in part one, I am going to cover earth’s history from the start of life to the evolution of our hominin ancestors, from 4.6 billion years ago to around six million years ago. For some, this will be all new information and for others a bit of a refresher; for everyone, if you have questions, please don’t hesitate to ask. 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