Divvying Up Baby

I recently bought my baby new pajamas with a decal that says, “50% Dad + 50% Mom = 100% Me!” I couldn’t resist an outfit that doubles as both math and biology lessons. But on further reflection, I’ve realized that this simple formula is wrong in more ways than one.

To begin with, my baby doesn’t look like she’s 50% Mom. At best, she looks about 10% Mom. I’ve written before about how our daughter would be a mixture of traits from European and Indian peoples, reflecting her mom and dad’s respective heritages. Yet she arrived looking like a wholly Indian baby. This is fine, of course. I think she’s absolutely perfect with her caramel skin and jet black eyes and hair. But it’s hard to keep a straight face when friends politely ask us who we think she resembles. And when I’m out with her in public I’m aware that I look like her nanny, if not someone who’s stolen a baby. She truly doesn’t look like she’s mine.

How else is the formula wrong? Genetically. Sure, our daughter’s nuclear genes are comprised of DNA sequences from both my husband and me. But she has another sort of DNA in her body, one that literally outweighs the conventional type. This DNA lives in her mitochondria, the bacteria-like structures that populate our every cell. Mitochondria are like tiny internal combustion engines, generating all of our energy through respiration and releasing heat that makes us warm-blooded animals. Although mitochondria don’t have many actual genes, they each carry several copies of those genes. Multiply that by the 10 million billion or so mitochondria in our bodies and you’ll find that we each contain more DNA by weight for mitochondria than humans. And these mitochondrial genes are inherited entirely from the mother.

Mitochondrial genes can’t claim credit for your eye color, jaw shape, or intrinsic disposition. Their reach is mostly limited to details of your metabolism and your susceptibility to certain diseases. But mitochondrial DNA is significant for another reason: scientists use it to trace human lineages across the globe. After all, they don’t get reshuffled in each generation as our nuclear genes are. Mitochondrial inheritance can be traced back hundreds of thousands of years, following the maternal lineage at every generation. Unlike the historian’s genealogy, which often follows surnames passed down from fathers, the scientist’s genealogy is a tree built of mothers alone.

So it is through our mothers that our heritages can be traced into the distant past. In every one of her cells, my baby carries a map leading back through me and my mother and her mother and beyond . . . unbroken all the way back to our earliest origins as modern humans. And since my baby is a girl, she can continue that line. So long as she has a daughter and she has a daughter and so on, I will remain a part of that ongoing chain.

My condolences to all you men out there. Same to all you women who only had sons. You’ve passed on your nuclear genes and your child may be the spitting image of you, but your mitochondrial chain has been broken and you will be left out of the biologist’s tree. Although my daughter looks classically Indian, her mitochondrial DNA reveal only her European lineage. Despite the hair, eyes, and skin she inherited from her daddy, my baby’s mitochondria are mine all mine. She and I are links in a traceable chain of human life while my husband is nowhere to be found.

That’s something I can remember the next time I’m mistaken for the nanny.


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.

Six Loves Seven

Ever since I was a child, numbers have been boys or girls. I remember moments of boredom in second grade when I looked at the number line stretched out above the chalkboard and made up stories about the digits between 3 and 9. (For some reason, 1 and 2 were too small to interest me much.) The numbers 3, 5, 6, and 9 were male, while 4, 7, and 8 were female. Six was in love with 7 and sought love advice and pick up lines from the clever trickster 5, the Cyrano de Bergerac of numbers. Meanwhile, 8 was the silent, wise woman, advising her neighbor and protégée 7 toward caution. To this day, when I call to mind these digits, their personalities and genders are as tied up in their meaning as their numerical representation. Just as 7 will eternally be the sum of 3 and 4, in my eyes it will always and forever be a girl.

My foray into the love life of digits may or may not be typical, but we all personify the world around us. Children naturally personify their teddy bears or action figures. Adults often name and genderize their cars, musical instruments, or gadgets. Historically, boats are given genders, as are ‘mother countries.’ Consider the success of Tron, a movie based on personifying computer programs. Consider the fan clubs devoted to Roombas (small, automated vacuum cleaners), and the many people who call them ‘cute’ or think of them as pets. We have one of those handy little guys, and when he is roaming around the house, I can’t help but think of him as alive.

Certain types of objects or concepts evoke personification more than others. Things that move or interact with us. Things that are important to us or that we rely upon. And certainly, things whose workings we don’t understand or can’t control. When our computer or television isn’t working, don’t we yell at it and talk to it? Isn’t there some frustration that comes from the fact that it’s not cooperating, like a stubborn child? When a vending machine “steals” our money, do we strike it merely because we think it will magically release our bag of Fritos? Or isn’t part of the reason because we’re angry at its bad behavior? It has acted unfairly; it has taken our money and reneged on its end of the deal.

Before the modern era of scientific gadgetry and examination, the whims of weather, reproduction, disease, and death were mysterious and fickle. Imagine how terrifying life would have been in such an extreme and unpredictable world, when harvests could be ruined without reason and infants struck down with inexplicable pox. It was in our nature, as creative, thinking beings, to explain the unexplainable. To create a framework in which we could try to understand the world, and in doing so, control it.

Should it surprise us that, since ancient times, societies the world over have developed mythologies and religions with anthropomorphic gods? We are inherently social animals and it is in our nature to think in terms of conscious entities with thoughts and emotions like ours. We know how to behave with each other, and if the gods are like us, then we know how to behave with them. We can make offerings to them, please them, appease them. We can win their favor, and in doing so, win ourselves good fortune. By conceptualizing the world in terms we understand, we believe we gain some purchase on our fate.

Now when I see children talking to their stuffed animals, bandaging their wounds or serving them tea, I think that they are practicing. When I remember my younger self, enraptured by the love affair of numbers 6 and 7, I think that I was in training. Like other children, I was just beginning to try to make sense of this world.

Dumb Kids

I had an unpleasant experience in the car today. For the first time, I listened carefully to the lyrics of Van Morrison’s Brown Eyed Girl. You know, the one requested by brown eyed girls everywhere and played at dances as a romantic upbeat song. I could sing all of the lyrics, but had never really listened to what I was singing.

Here’s the last verse:

So hard to find my way,
Now that I’m all on my own.
I saw you just the other day,
My, how you have grown!
Cast my memory back there, Lord
Sometimes I’m overcome thinkin’ ‘bout
Makin’ love in the green grass
Behind the stadium
With you, my brown eyed girl
You my brown eyed girl.

It’s a break up song! Some of you may have known this, but my fiancé and I were shocked and saddened. He said I’d ruined the song for him. We moved it to a different, sadder playlist. How could we have sung lyrics we’d never even listened to?

I had a similar discovery about the 80’s song Second Chance by 38 Special. The clearly-enunciated bridge contains the following lyrics:

I never loved her
I never needed her
She was willing and that’s all there is to say.
Don’t forsake me;
Please don’t leave me now.

She was willing? The song went from nostalgic to disturbing. I still listen to it, but with much less glee.

It’s true of movies too. I knew all of the lines to The Breakfast Club growing up but didn’t realize until adulthood that it wasn’t cigarettes they were smoking and that they didn’t get silly just because they’d become friends. And I didn’t figure out that there was an abortion in Dirty Dancing until years afterward.

It got me to wondering: how could I have loved these movies and learned the lyrics to these songs without understanding what they were about? And not even understanding that I didn’t understand?

It occurs to me that kids can’t get too hung up on what they don’t understand. If they did, they wouldn’t be able to enjoy most of what they saw or heard. They make sense of what they can and move on, oblivious and happy. That’s why Disney can sneak adult humor into movies without children noticing. And that’s why it wasn’t until today, in the car, that I learned the truth about the brown eyed girl.

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