2006, and graduate students from the University of Hawaii, I compiled nearly four hundred groups of siblings, over a thousand faces, cutting and pasting their senior photos (to control for age), organizing them in family groups—some large, some small. To be included in the study, families needed to have at least two siblings born within two years of each other. Just as with the celebrity siblings, among those pictured in the yearbooks, family beauty generally faded according to the same pattern. From oldest to youngest, the jaw grew narrower and receded, the cheekbones flattened out, and the eyes were less deeply set. The closer in age the siblings, the more striking the changes. Unfortunately, birth spacing alone does not prevent this effect. With anything short of an optimal dietary context, if mom’s body is asked to produce large numbers of children, then each subsequent baby uses up more of her reserves so that, even with three to four years between births, her body continues to lose nutritional ground. This can magnify the effects of developmental inequalities down the line.
What all these subtle—and sometimes not-so-subtle—rearrangements of the facial features amount to is a loss of dynamic symmetry which, for reasons that have as much to do with health and function as they do with looks, is unlikely to be associated with improvement in quality of life. This may make it seem as though first-born babies have all the advantages. But when we’re talking about a baby growing inside mom on a less-than-ideal diet, going first to get a better shot at being more dynamically symmetrical can actually come at a price.
hormonal receptivity.
The first-born might have one eye bigger than the other, or a slightly rotated jaw that ever so subtly torques their smile. One half of the face might be slightly larger than the other. After this discovery I started checking my patients with Temporomandibular Joint Pain (TMJ, or jaw joint pain) for this asymmetry and found it, most often in those with the most long-standing symptoms. At least in my small sample size of several dozen, these patients were usually the first-born children.
As it turns out, the medical literature is peppered with reports of biradial asymmetries occurring more often in first-born children: leg length discrepancy,140 congenital hip dysplasia,141 scoliosis,142 plagiocephaly (flattening on one side of the skull),143 facial asymmetry including flattening of one cheek with prominence of the other,144 and left-right asymmetries of the jaw.145, 146 The authors of such articles generally suggest a link between these disruptions in biradial symmetry and “uterine crowding”—a simple lack of adequate space.147
As I see it, we are witnessing two distinct patterns of symmetry disruption, one occurring in first-born children attributable to insufficient uterine expansion, and the other occurring in subsequent children attributable to inadequate nutrition. The problem of inadequate space correlates with a loss of biradial (left-right) symmetry, while the problem of inadequate nutrition correlates with a loss of dynamic symmetry (parts losing their ideal relative proportion).
We’ve already discussed a potential explanation for relative nutritional deficits in later-born children being simple resource depletion and an inadequate period of time to allow the replenishing of mom’s nutritional reservoir. What could be the cause of inadequate uterine growth? This, I believe, has to do with hormones.
The more extreme version of a lack of uterine space is called intra-uterine growth retardation, and refers to a fetus that has failed to achieve its genetically determined growth potential. It affects between 5 and 10 percent of pregnancies, most commonly in smokers.148 Affected newborns suffer lung problems, potentially serious bleeding, and a host of other life-threatening issues. Long-term consequences include cerebral
palsy, developmental delay, and behavioral dysfunction.149 Researchers are recognizing the role of chemical interference from oxidation in disrupting the normal responsiveness of the uterus to hormones like estrogen, progesterone, and more.150, 151 As we’ll see in later chapters, two foods that most powerfully promote oxidative stress are vegetable oils and sugar. In other words, too much vegetable oil and sugar in mom’s diet create chemical interference, delaying signal transmission between mom’s body and her own uterus. This type of symmetry shift is most pronounced in the first pregnancy due to the fact that, by the second pregnancy, the uterus has been prepped by the first, which is why the second delivery typically goes faster.
It’s important to keep in mind that very few of us are perfectly biradially symmetrical, and that minor differences in leg length, for example, should not be considered a matter of great concern. It is only when the asymmetry is pronounced that it is likely to lead to significant musculoskeletal issues down the road.
There is however one situation in which the human body is pushed to such extremes, and the loads that are communicated through the kinetic chain generate such powerful forces that, over time, even relatively nominal asymmetries can potentially pose a problem. Here, I’m talking about serious athletes, both professional and amateur. Because these subtle asymmetries can leave an athlete susceptible to repetitive motion injuries or changes in gait and movement, athletic trainer Timothy DiFrancesco of the L.A. Lakers includes symmetry analysis when sizing up a potential recruit: “Performance specialists in the NBA and elsewhere are always looking for the most valid and reliable ways to assess musculoskeletal asymmetry levels. This helps give critical insight into injury susceptibility and an athlete’s ability to withstand the rigors of the sport.”
BIRADIAL SYMMETRY CAN BE A PAIN IN THE NECK
Asymmetry leads to compensation throughout the skeleton.
When the skeleton is just standing there, you can imagine the forces of gravity causing pain. Now imagine the skeleton doing something really athletic. You don’t have to a be a world-class trainer to imagine this degree of symmetry could cause a person pain. The kinds of discrepancies people like Tim DiFrancesco are looking for are of course far more subtle—partly because if they weren’t, the athlete would not likely have made it to elite sports.
I’d like to introduce one additional twist on the Sibling Symmetry Shift. I discovered that some second-born females have fuller lips and more sexually appropriate chins and eyebrows than their older siblings—
a woman’s chin being a little more pointed and less squared than a man’s, and a woman’s eyebrows being more arched while a man’s are lower and straighter. The pointier female chin and gracefully curved eyebrows are examples of sexual dimorphism, the differential development between males and females (introduced in Chapter 4).
Human males, in addition to strong, squared chins, tend to have broad shoulders, while women, along with more petite and rounded chins, have slender shoulders, narrow rib cages, wider hips, and fatty breast tissue. So what would explain these second-born girls with the more attractive, sex-specific features?
A woman’s body undergoes a miraculous change soon after conception. Under the influence of a new physiologic directive, the functioning of every organ is altered by waves of hormones, all generated by the tiny collection of rapidly dividing cells. Many of these changes are permanent. Of course, no organ is affected more obviously than the uterus. But a modern diet interferes with hormonal signaling, as we’ll see later, so the uterus, in particular, can’t perform quite so well, at least not at first. Blunted uterine (and placental) estrogen signals could explain why estrogen’s effects on a first baby girl often appear diminished. A subdued response to estrogen can lead to relatively masculine features: slightly too prominent brow and chin, aggressive-looking eyebrows, and lips not quite filled out. She may be handsome, but she won’t turn heads. With mom’s uterine infrastructure already built out by the second pregnancy, the same level of estrogen produces a more potent response. Incidentally, if the second sibling were a boy, the burst of estrogen receptivity might still create a feminizing effect, sharpening the center of the chin, arching the eyebrows, rounding the forehead, and plumping the lips.
So what does this mean? For one thing, although the development of a beautiful, healthy baby is—as we are so fond of saying—miraculous, it is not a mystery. This spectacular orchestration of events is as dependent upon a strict total adherence to a program of good nutrition as it is vulnerable to its breach. Studying siblings enables us to see why we aren’t all perfect, and allows us to witness how nutrient deficits change a child’s growth in ways that are both predictable and easy to measure.
I call it the Sibling Symmetry Shift because the subtle effects of maternal malnutrition on a child’s growth are most readily discernable in the faces of children born in a short time period after an older sibling who, presumably, shares similar genes and thus serves as a kind of
control. But as I just described, no child, not even an only child, is immune from symmetry shifts because the underlying problem is not birth order; it’s malnutrition. While a first baby grows in mother’s womb, static interference from dietary sugar and vegetable oils too often disrupts hormonal communication between placenta, uterus, and ovaries, delaying uterine development and reducing physical space for the baby while tending to blunt the child’s potential for sexual dimorphism. In a woman’s subsequent children, the cellular circuits necessary to coordinate the various baby-making stations (uterus, placenta, etc.) have already been optimized, enabling faster uterine responses (such as quicker growth and speedier deliveries), which permits greater biradial symmetry, and primes the baby’s potential for sexual differentiation. But in the context of a modern diet, the cost of going second (particularly with close birth intervals) is often relative maternal nutrient deficiencies that result in relatively less material to build bone, nerve, and so on, thinning and flattening facial features to create a worn-down look.
In Chapter 3, we saw that the vast majority of Americans—and I mean just about everyone—aren’t merely malnourished, but severely malnourished. Which should make you wonder: Doesn’t that mean we’re all suffering from some degree of symmetry shifts? Most of us are, which is why there seems to be so few genetic lottery winners walking around.
And what explains them? How did they, raised by parents who, presumably, followed the same advice my parents did, and ate the same steady diet of frozen, canned, and vitamin-poor fruits and vegetables, mystery meat from poisoned animals, grains grown on mineral-depleted soils, margarine, and everything else that makes our modern diet unhealthy, curry Mother Nature’s favor? They didn’t. Their great-great-grandparents did, by eating such nutrient-rich diets that they imparted the family epigenome with genetic momentum, the ability of genes to perform well with suboptimal nutrient inputs for a finite amount of time.
And their placentas did, by sending an especially urgent message to mother’s bones, brain, skin, muscles, glands, and organs, to release every available raw material for the benefit of the baby. In these one-in-a-million cases, the fetal genome operating in mom’s belly can do what it’s
been doing for a hundred thousand years: create the miracle of a perfectly symmetrical Homo sapien baby.
I should be clear that my investigation into the relationships between symmetry shifts and birth order and timing barely scratches the surface.
I certainly don’t mean to suggest, by introducing my observations, that we can find this pattern in every family without exception. Rather, I’m describing a tendency that I think bears consideration. Nor do I mean to suggest that parents are to blame when congenital malformations affect their children. My hope is that this kind of information will help us do away with the idea that baby-making is simply too formidable or mysterious a task to try to optimize and that we might as well just throw our hands in the air and attribute life-changing symmetry shifts to factors entirely beyond our control.
I believe that we can offer moms solid information to more effectively incentivize their adherence to a healthy diet. What moms need, what they want, is a strategy. A strategy that can help ensure that when their bodies are called upon to engage in the serious project of creating a healthy baby they are nutritionally prepared to allow all those interacting growth-directing systems to join in a coordinated effort. And the proliferation of mommy chat rooms and advice-sharing platforms proves that millions of mothers-to-be are already well aware of the profound impact of nutrition and hungry for the best advice. Given the increase in birth defects, autism, child asthma, child depression, child cancer, and so on that I’ve observed in the decades since my graduation, years ago I began to suspect that the current strategy—the one recommended by the experts moms most often listen to—has proven to be an epic failure. Nevertheless, I’d sorely underestimated the barriers to disseminating better, more effective child-health–fortifying information by way of the medical establishment.