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OUR BABIES, OURSELVES PART 5: The Evolution of Breastfeeding

by Sarah on February 16th, 2011

I’ve decided to split the breastfeeding chapter into two parts because there’s so much valuable information in it. I was so interested to learn how breastfeeding came about, and I hope you find it interesting too!

About 65 million years ago (some time after dinosaurs went extinct) a group of small egg-laying animals began to flourish. These animals had a small warming patch on their chests which, when sitting on their eggs, gave off heat. The patches must have also had a gland which secreted a liquid, and it is presumed that the animals’ offspring at some point began to lick up some of the liquid to hydrate themselves.

The liquid turned out to be good for the babies’ immune systems because those who licked it grew bigger or faster, and were healthier. This “maternal ooze” eventually evolved into being even more nutritious so that it could keep the babies’ satisfied whilst their mom was out looking for food. And so lactation was born!

The gland would’ve started off being more of a sweat gland, but would’ve slowly become one which could “synthesize  proteins, carbohydrates and lipids rather than just excrete water” (p.181). Eventually, these little animals began giving birth to live young, but what made them most different from reptiles and birds was that they lactated to feed their young.

This idea of how breastfeeding came about is only a theory, but a very strong theory, based on fossil evidence. It’s supported by creatures living today, like the duck-billed platypus, which lays eggs but also lactates. Amazing!

It makes sense that lactation came about, because it made the lives of the mothers and their young so much easier. Moms could go looking for just one type of food for themselves (not an easier one to digest for their young as well) and then their bodies would convert this food into milk. When breastfeeding, infants could stay in the nest, being protected from predators. And of course, there is the bonding which comes during nursing. “…physicality initialises an attachment that can be beneficial for both in the long term in social species where interpersonal connections become so important to daily life”. (p.183)

Humans evolved into a separate species about 1.5 million years ago. At this point we were walking upright, and because we had no hair on our bodies for our infants to cling to, we held onto them to keep them safe. Presumably on our hips. This gave our babies easy access to our breasts, and so it was easy for a baby to feed continuously, latching whenever they chose. As I mentioned before, many cultures still follow this practice. For example, !Kung San infants feed every thirteen minutes on average.

It’s really difficult to tell how long infants breastfed for before they were weaned, but anthropologist, Katherine Dettwyler, has worked out an average based on a few different factors. She’s looked at how long different types of monkeys breastfeed for and then compared humans to that, based on their size and how long they are pregnant for. She’s also looked at when different types of primates begin to cut their teeth. Based on all this, she estimates that human infants are designed to be weaned somewhere between two and a half and seven years! Weirdly, this ties in exactly with today’s cross-cultural data. Only Westerners wean before the age of one. Through analysing bones from humans who lived just a few thousand years ago it can be seen that humans main source of food was breast milk up until the ages of two and three.

So, what evolution tells us is that throughout 99% of human history, babies drank breast milk as their main or sole food until at least two or so years, and were then slowly weaned over another few years.

I know that in our Western culture this is such a touchy subject, with toddlers who try to grab their mom’s breast being heavilyfrowned upon. I just recently found myself in the middle of a conversation where some seriously strong adjectives were thrown around when the mention of toddlers or older children being breastfed was mentioned. Isn’t it strange. Somehow, society has created its own new rules (based on who knows what!). The people who follow what our bodies have been designed for, and what we’ve been doing for millions and millions of years, are labelled as weird. Sometimes I can’t stop worrying that the world’s turned upside down!

(Image via 007 Breastfeeding)