Halfsies!

My husband spotted another one yesterday. A half-Indian, half-Caucasian blend. The woman had an Indian first and last name, but her features were more typical of a Persian ethnicity than either Indian or white. My husband overheard her describing her heritage and smiled. These days, with a half-Indian, half-white baby on the way, we’re hungry for examples of what our baby might look like. We’ve found a few examples among our acquaintances and some of my husband’s adorable nieces and nephews, not to mention the occasional Indian-Caucasian celebrity like Norah Jones. We think our baby will be beautiful and perfect, of course, although we’re doubtful that she’ll look very much like either one of us.

Many couples and parents-to-be are in the same position we are. In the United States, at least 1 in 7 marriages takes place between people of different races or ethnicities, and that proportion only seems to be increasing. It’s a remarkable statistic, particularly when you consider that interracial marriage was illegal in several states less than 50 years ago. (See the story of Loving Day for details on how these laws were finally overturned.) In keeping with the marriage rates, the number of American mixed race children is skyrocketing as well. It’s common to be, as a friend puts it, a “halfsie.” At least in urban areas like Los Angeles, being mixed race has lost the negative stigma it had decades ago and many young people celebrate their mixed heritages. Their unique combinations of facial and physical features can be worn with pride. But the mixture goes deeper than just the skin and eyes and hair.

At the level of DNA, all modern humans are shockingly similar to one another (and for that matter, to chimpanzees). However, over the hundreds of thousands of years of migrations to different climates and environments, we’ve accumulated a decent number of variant genes. Some of these differences emerged and hung around for no obvious reason, but others stuck because they were adaptive for the new climates and circumstances that different peoples found themselves in. Genes that regulate melanin production and determine skin color are a great example of this; peoples who stayed in Africa or settled in other locations closer to the Equator needed more protection from the sun while those who settled in sites closer to the poles may have benefited from lighter skin to absorb more of the sun’s scarce winter rays and stave off vitamin D deficiency.

In a very real way, the genetic variations endemic to different ethnic groups carry the history of their people and the environments and struggles that they faced. For instance, my husband’s Indian heritage puts him at risk for carrying a gene mutation that causes alpha thalassemia. If a person inherits two copies of this mutation (one from each parent), he or she will either die soon after birth or develop anemia. But inheriting one copy of the gene variant confers a handy benefit – it makes the individual less likely to catch malaria. (The same principle applies for beta thalassemia and sickle cell anemia found in other ethnic populations.) Meanwhile, my European heritage puts me at risk for carrying a genetic mutation linked to cystic fibrosis. Someone who inherits two copies of this gene will develop the debilitating respiratory symptoms of cystic fibrosis, but thanks to a handy molecular trick, those with only one copy may be less susceptible to dying from cholera or typhoid fever. As the theory goes, these potentially lethal mutations persist in their respective populations because they confer a targeted survival advantage.

Compared to babies born to two Indian or two Caucasian parents, our baby has a much lower risk of inheriting alpha thalassemia or cystic fibrosis, respectively, since these diseases require two copies of the mutation. But our child could potentially inherit one copy of each of these mutations, endowing her with some Suberbaby immunity benefits but also putting her children at risk for either disease (depending on the ethnicity of her spouse).

The rise in mixed race children will require changes down the road for genetic screening protocols. It will also challenge preconceived notions about appearance, ethnicity, and disease. But beyond these practical issues, there is something wonderful about this mixing of genetic variants and the many thousands of years of divergent world histories they represent. With the growth in air travel, communication, and the Internet, it’s become a common saying that the world is getting smaller. But Facebook and YouTube are only the beginning. Thanks to interracial marriage, we’ve shrunk the world to the size of a family. And now, in the form of our children’s DNA, it has been squeezed inside the nucleus of the tiny human cell.

Locked Away

The results are in. The ultrasound was conclusive. And despite my previously described hunch that our growing baby is a boy, she turned out to be a girl. We are, of course, ecstatic. A healthy baby and a girl to boot! As everyone tells us, girls are simply more fun.

As I was reading in my pregnancy book the other day, I came across an interesting bit of trivia about baby girls. At this point in my pregnancy (nearly 6 months in), our baby’s ovaries contain all the eggs she’ll have for her entire life. As I mentioned in a prior post, the fact that a female fetus develops her lifetime supply of eggs in utero represents a remarkable transgenerational link. In essence, half of the genetic material that makes up my growing baby already existed inside my mother when she was pregnant. And now, inside me, exists half of the genetic material that will become all of the grandchildren I will ever have. This is the kind of link that seems to mix science and spirituality, that reminds us that, though we are a mere cluster of cells, there’s a poetry to the language of biology and Life.

But after stumbling upon this factoid about our baby’s eggs, I was also struck by a sense that somewhere someone seemed to have his or her priorities mixed up. If our baby were born today, she would have a slim chance of surviving. Her intestines, cerebral blood vessels, and retinas are immature and not ready for life outside the womb. Worse still, the only shot her lungs would have at functioning is with the aid of extreme medical intervention. The order of it all seems crazy. My baby is equipped with everything she’ll need to reproduce decades in the future, yet she lacks the lung development to make it five minutes in the outside world. What was biology thinking?

Then I remembered two delightful popular science books I’d read recently, The Red Queen by Matt Ridley and Life Ascending by Nick Lane. Both described the Red Queen Hypothesis of the evolution of sex, which states that the reason so much of the animal kingdom reproduces sexually (rather than just making clones of itself) is to ‘outwit’ parasites. In short, if each generation of humans were the same as the next, parasites large and microbial could evolve to overtake us. By mixing up our genetic makeup through sexual reproduction, we make it harder for illnesses to wipe us out. Like the Red Queen from Lewis Carroll’s classic, we keep running in order to stay in the same place (which is one step ahead of parasites and disease).

Just as there are parasitic organisms and bacteria, one might say that there are parasitic genes. For example, mutations in the DNA of our own replicating cells can cause cancer, which is essentially a self-made, genetic parasite. Moreover, retroviruses like HIV are essentially bits of genetic material that invade our bodies and can insert themselves into the DNA of our cells. And the ultimate road to immortality for a parasitic gene would be to hitch a ride on the back of reproduction. Imagine what an easy life that would be! If a retrovirus could invade the eggs in the ovaries, it would be passed on from one generation to the next without doing one iota of work. It’s the holy grail of parasitic invasion – get thee to the ovaries! According to Matt Ridley in another of his books, The Origins of Virtue, the human germ line is segregated from the rest of the growing embryo by 56 days after fertilization. Within two months of conception, the cells that will give rise to all of the embryo’s eggs (or sperm, in males) are already cordoned off. They are kept safe until they are needed many years in the future.

So perhaps my little baby’s development isn’t as backwards as it seemed at first. Yes, lungs are important. But when you’ve got something of value to others, it makes practical sense to hurry up and lock it away.

The Trouble with (and without) Fish

Once upon a time in a vast ocean, life evolved. And then, over many millions of years, neurons and spinal cords and eyes developed, nourished all the while in a gentle bath of nutrients and algae.

Our brains and eyes are distant descendants of those early nervous systems formed in the sea. And even though our ancestors eventually sprouted legs and waddled out of the ocean, the neural circuitry of modern humans is still dependent on certain nutrients that their water-logged predecessors had in abundance.

This obscure fact about a distant evolution has recently turned into a major annoyance for me now that I’m pregnant. In fact, whether they know it or not, all pregnant women are trapped in a no-win dilemma over what they put into their stomachs. Take, for instance, a popular guidebook for pregnant women. On one page, it advocates eating lots of seafood while pregnant, explaining that fish contain key nutrients that the developing eyes and brains of the fetus will need. A few pages later, however, the author warns that seafood contains methylmercury, a neurotoxic pollutant, and that fish intake should be strictly curtailed. What is a well-meaning pregnant lady to do?

On a visceral level, nothing sounds worse than poisoning your child with mercury, and so many women reduce their seafood intake while pregnant. I have spoken with women who cut all seafood out of their diet while pregnant, for fear that a little exposure could prove to be too much. They had good reason to be worried. Extreme methylmercury poisoning episodes in Japan and Iraq in past decades have shown that excessive methylmercury intake during pregnancy can cause developmental delays, deafness, blindness, and seizures in the babies exposed.

But what happens if pregnant women eliminate seafood from their diet altogether? Without careful supplementation of vital nutrients found in marine ecosystems, children face neural setbacks or developmental delays on a massive scale. Consider deficiencies in iodine, a key nutrient readily found in seafood. Its scarcity in the modern land-based diet was causing mental retardation in children – and sparked the creation of iodized salt (salt supplemented with iodine) to ensure that the nutritional need was met.

Perhaps the hardest nutrient to get without seafood is an omega-3 fatty acid known as DHA. In recent years, scientists have learned that this particular fatty acid is essential for proper brain development and functioning, yet it is almost impossible to get from non-aquatic dietary sources. At the grocery store, you’ll find vegetarian products that claim to fill those needs by supplying the biochemical precursor to DHA (found in flaxseed, walnuts, and soybean oils), but we now know that the precursor simply won’t cut it. Our bodies are remarkably slow at synthesizing DHA from its precursor. In fact, we burn the vast majority of the precursor for energy before we have the chance to convert it to DHA.

So pregnant women must eat food from marine sources if they are to meet all the needs of their growing babies. Yet thanks to global practices of burning coal and disposing of industrial and medical waste, any seafood women eat will expose their offspring to some amount of methylmercury. There’s no simple solution to this problem, although recent studies suggest that child outcomes are best when women consume ample seafood while avoiding species with higher levels of methylmercury (such as shark, tilefish, walleye, pike, and some types of tuna). Of course much is still unknown. Exactly how much DHA intake is enough? And since mercury levels vary based on where the fish was caught and what waste was released nearby, you can never be sure it’s safe to eat.

Unless we start cleaning up our oceans, pregnant women will continue to face this awful decision each time they sit down at the dinner table. Far worse, we may face future generations with lower IQs and developmental delays regardless of which choice their mothers make. Thanks to shoddy environmental oversight, we may be saddling our children with brains that don’t work as well as our own. And that is something I truly can’t swallow.

Guessing at Sex

Something’s happened. Something both miraculous and mundane. Over the past few months I’ve been transformed from a woman into an incubator. A walking, talking (and often eating and napping) incubator programmed to provide the perfect environment for a growing baby . . . something. We’ll find out the gender in a couple weeks. Still, it’s always the first question people ask when they hear that I’m pregnant: “Is it a boy or a girl?” And since we haven’t had an answer for them, my husband and I have been showered with an astonishing number of guesses. It seems that everyone we’ve ever met is secretly a gender-divining expert.

They all have their methods. One woman had me turn around so she could size up my back fat. “If you gain weight in the back, it means you’re having a boy,” she explained. Another examined my face as she explained her theory that women who carry a girl look more beautiful (thanks to the added female hormones) while those carrying a boy start looking more, well, dude-like. Others have sworn by the shape of the belly – if the stomach looks pointed versus broad. One acquaintance asked for the baby’s fetal heart rate, saying that babies with faster heart rates always turn out to be girls. Another friend described her theory that the mother’s personality predicts the baby’s sex; apparently, soft-spoken mothers tend to have boys.

I like when people guess the gender. It’s interesting to hear their varied theories and sweet to think that they’re excited enough about our pregnancy to venture a guess. It makes a personal, biological experience more communal. But I can’t say much for their accuracy. So far, the guesses have been evenly split between boy and girl.

That’s the thing about guessing gender; with a 50-50 chance of either outcome, it’s unimpressive if you’re right and even more unimpressive if you’re wrong. And yet with such odds, it’s only natural that people start thinking they’ve hit on a good heuristic. No matter how wrong your method, you will, on average, be right 50% of the time. That already subjectively feels like a lot of rightness. If you try your method out on a small number of people to start, you could wind up with a lower success rate (by chance) and perhaps abandon your technique, but you might luck out and guess right 75% of the time or higher, at least for a little while. Someone who starts out on a lucky streak may well become a diehard believer who swears by his method, even after his batting average declines.

There’s simply no way that so many people can be so sure of their gender-guessing strategies unless they pick and choose their outcomes. Or unless, as I suspect, their memories do it for them. Consider the conundrum of the grocery store line. Many of us believe we are cursed (or mysteriously inept) at choosing a checkout lane at the grocery store. No matter which line we wind up in, it turns out to be the slowest. If we switch to another, that one mysteriously slows down. You rarely hear about the reverse – people who claim to have a special gift for picking the fastest lane. How can the majority of people be below average at the same task? If their memories are skewing the results. We never notice and remember the times we breeze right through checkout or overtake our neighbors in the next line over. The salient events – and the ones we’ll remember – are the times we’ve been stuck behind someone arguing prices or heaping coupons on the counter. Times when six people go by in the next line over while your food wilts and thaws on the conveyor belt.

It must be the same with guessing gender. When people are right, they are ecstatic and vindicated. When they are wrong, they notice and remember it less. And those that do notice their error may wonder if they misjudged the belly shape or back fat. The problem wasn’t necessarily with the heuristic, but rather with its execution. If only the pregnant lady’s dress had been tighter or if the guesser hadn’t been distracted by hors d’oeuvres, the method would certainly have worked!

I am by no means immune to these twisted ways of thinking. I can’t help but believe that I’m cursed at picking grocery lines. And I also seem to have a guess about this baby’s gender. For no apparent reason, I have it in my head that the baby is a boy. No heuristic here, just a feeling I can’t seem to shake. It’s not that I’d prefer a boy – I’d be equally delighted to have a girl. And I know that there’s no scientific merit to the inkling. Even if a woman could tune into some subtle something in her body and know, she’d need prior experience to compare it to. This being my first pregnancy, I have no idea what it might feel like to carry a boy versus a girl, if such a thing were even possible. So I should put no stock in such a feeling.

And yet when the ultrasound rolls around, I know I’ll be surprised if we learn that the baby’s a girl. Equally happy and excited, to be sure. But most definitely (and illogically) surprised.

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