Wednesday, May 13, 2015

Just-So Babies

If you've ever watched a baby eat solid foods, that's DuckFace.

If you've ever seen a shirtless baby, that's DadBod.

Why are we so into these things, whatever they are, right now?

Because whether we realize it or not, they're babylike, which means they're adorable. And all things #adorbs are so #totes #squee right now for the millions (billions?) of social media users in our species. And if they're babylike, they're especially adorable to women and women are more frequently duckfaces than men. And women are increasingly open to embracing, maritally, the non-chiseled men of the world...who knew?

Well, anyone and everyone who's spent a damn second raising a baby, that's who. Especially those with mom genes.

Understanding babies, how they develop, and our connections to them while they do so is key to explaining just about everything, and perhaps literally eh-vuh-ray-thing, about humanity. 
How can I be so sure? Well aren't you?

We all know that the most attractive women are the ones that look like babies. 

And to help Nature out, makeup, lasers, and plastic surgery neotenize us temporarily or permanently, making our skin smooth, our eyes big, our lips pouty, our cheeks pinchable and rosy, and our noses button-y.

That stuff about beauty is common knowledge isn't it? We do these things to ourselves because of our evolved preferences for babies. We find them to be so extremely cute that this adaptive bias for babies affects much of the rest of our lives. Beauty is just the tip of the iceberg because, like I said, babies explain everything: DuckFace, DadBod, ...

And, yes, I do have more examples up my sleeve.

All that weight we gain while pregnant? You think it's to stockpile fat for growing a superhuge, supercharged baby brain both before and then after it barely escapes our bipedal pelvis?

Me and Abe, with hardly an inkling that there's still a whopping five more weeks ahead of us... suckers.
Or maybe I gained 20 pounds above and beyond the actual weight of the pregnancy so that I could protect my baby from calorie lulls from disease or food shortage, especially when those things happened more frequently to my ancestors.

Nope. And nope.

Pregnant women gain all that weight so that its lightning fast loss while lactating leaves behind a nice saggy suit of skin for the baby to grab and hold onto--not just on our bellies, but our arms and legs too. Our ancestors were dependent on this adaptation for quite a while, but over time mothers and infants became less dependent on it when they started crafting and wearing slings. Slings reduced selection on a baby's ability to grasp, you know.

Before slings, selection would have been pretty intent on favoring baby-carrying traits in both mothers and babies. For example, t
he way that our shoulder joints are oriented laterally, to the side, is unlike all the apes' shoulders which are oriented more cranially, so they're always kind of shrugging. You think we have these nice broad shoulders for swinging alongside us while running, for seriously enhancing our throwing ability, and, of course, for making stone tools? 

No. No. No.

All that's great for later in our lives, but our lateral facing shoulder joints are for being picked up and carried around while we're helpless babies. Our sturdy armpits are necessary for our early survival. And, biomechanically, those shoulder joints are oriented in the optimal way for carrying babies too. It's a win win. Combine that with the shorter hominin forearm, oh, and that itty-bitty thing called hands-free locomotion and it's obvious that we're designed to carry our babies and also to be carried as babies.

Bums come into play here too.

You probably think your big bum's for bipedal endurance running don't you? Or you might assume it evolved to give a stone-tipped spear a lot of extra oomph while impaling a wooly rhino hide.

Wrong. And wrong again.

Our big bums develop early in life because, like armpits, they build grab'n'go babies as well as well-designed grown-up baby carriers.

Bums plop nicely on a forearm and most certainly give babies and moms an advantage at staying together. Bums on moms (if not completely liquefied and fed to baby) steady her while holding such a load and also provide something for a baby slung on her back to sit on. Once babies lost the ability to grasp onto moms, babies' bodies had to adapt to be portable objects and moms bodies had to adapt to never drop those portable objects (at least not too far). No doubt big bums, like sturdy armpits, evolved before slings and home bases were ubiquitous in our species. 

Here's another one: The pregnancy "mask."

All those pigmentation changes that we describe as a side effect of the hormones are much more than that. Those new brown and red blotches that grow on a mother's chest and face, those are functional. They're fascinators. A mother's body makes itself more interesting and loveable for the busy, brainy baby on its way. Once we started decorating our bodies with brown and red ochre and pierced shell, bones and teeth, selection on these biological traits was relaxed. But they still persist. Why not? A human baby can't be over-fascinated, can it?

Oh, and fire. That was the best thing that ever happened to babies which means it was the best thing that ever happened to everyone living with babies. Quiet, serene, fascination, those flames... which also happen to process food for toothless babies whose exhausted, stay-at-foraging parents, would much rather swallow the food they chew up for themselves.

The baby also grows fascinators of its own. The big long hallux. Yep. Our big toe is long compared to other apes'. This is where you say it's an adaptation for bipedalism but you'd be only half right.

© / Ingo Arndt / WWF
The length makes it easier to reach with our mouths, as babies. And we teethe on that big toe. Imagine a world with no Sophies! That's what our ancestors had to deal with. Toes as teething toys doesn't seem so ridiculous when you remember that our long thumbs evolved for sucking.

Anyway, this long hallux was a bit unwieldy so thanks to a lucky mutation we stuck it to the rest of the foot and this turned out to work rather well for bipedalism.

Now that it's been a few minutes into this post, you must be sitting there at your computer thinking about boobs.

Yep, babies explain those too! The aesthetic preference for large breasts, by both males and females, is just nostalgia and allometry. You know how when you go back to visit your old kindergarten it looks so tiny compared to your memory? While you're a small human, you spend quite a lot of time with breasts, focused intently on them. But grow your early impression of breasts up in proportion to your adult body's sense of the world and, well, that's quite a big silicon kindergarten!

Your desires, your preferences, your tastes, your anatomy now, your anatomy when you were a baby... everything is babies, babies, babies. Even bipedalism itself.

Gestating a large fetus would not be possible if we were not bipedal. Think about it. All apes are bipedal to a significant degree. What pressured us into being habitual bipeds? Growing big fat, big-brained babies, that's what. Can you imagine a chimpanzee growing a human-sized fetus inside it and still knuckle-walking? I doubt the body could handle that. The spine alone! If you walk upright and let your pelvis help to carry that big fetus, you're golden. Obviously it worked for us.

I could go on forever! But I'll just give you one more example today. It's one you didn't see coming.

Women live longer than men, on average, and a large portion of that higher male mortality rate (at older ages) is due to trouble with the circulatory system. Well, it's obvious why. I'm looking at my arms right now and, complementing these brown and red fascinators, another part of my new mom suit is this web of ropy blue veins. Is this because my baby's sucked up all my subcutaneous fat from under my saggy skin, or... Or! Is it because my plumbing's stretched after housing and pumping about 50% more blood than normal by the third trimester. If my pipes are now, indeed, relatively larger for my blood volume and my body size then, all things being equal, that should reduce my risk of clogging and other troubles. Most women experience a term pregnancy during their lives. I'm sure this explains most if not all of the differences in mortality between men and women.

Like I said, that's just the start. And although I haven't provided evidence for many of the things I wrote, that shouldn't matter. These are just-so stories and they're terribly fun to think about. They're nothing close to approximating anything as lovely as Kipling's but they're what we humans do. If you're not a fan of today's post, hey, it's not like it passed peer review!


Ken Weiss said...

A lush bit of entertainment from your pen, as usual! Of course, we'll want to know what Baby Abe thinks of all of this, when he's old enough to talk and not just duck-face. In any case, as our bodies fall apart in their various ineluctable ways, we can at least hope there are some good, solid reasons for it....such as those you suggest!

Holly Dunsworth said...

There are good reasons for every single thing about everything!
Can't wait to hear Abe's take.

Ken Weiss said...

Yes, good reasons for everything. Evolution's not a subject for babies, only for mature adults (desperate to find insightful-seeming explanations to publish?). Abe will straighten us all out, no doubt, if he's taught by his Mom.

Mango said...

Your son is adorable! Please forgive my ignorance, but I am curious, is there any research that supports any of the explanations you have provided for various traits possessed by babies and mothers? Or was your article meant only to entertain (which it did)? Thanks.

Holly Dunsworth said...

Mango, Thank you for saying so! And as far as I know, these are original stories. (I'm not claiming I'm the only or first to think them up.) My aim wasn't just to entertain myself and readers, but to, in between the lines, question whether some established evolutionary hypotheses are any better than these.