Monday, March 22, 2010

Blue-Eyed Parents ≠ Brown-Eyed Kids and Other Lies They Taught Me….

Way back when I was in 3rd grade or so, I got really interested in genetics. I’m not quite sure how it happened, but I remember taking out several books over the summer to find out how heredity worked. I ended up contemplating (seriously) whether both my grandmothers had been unfaithful to their husbands. Eventually, I came to the conclusion that I didn’t think so—not so much because I couldn’t possibly believe it of them (which embarrasses me somewhat now, since they were good women)—but because the timing seemed all off. Why did I come to this conclusion? Well, you see, all my grandparents had blue eyes. But both my mother and one of my father’s brothers had eyes that were decidedly brown. Blue eyes were recessive; brown eyes dominant. So blue eyed-parents weren’t supposed to have brown-eyed kids. But both the brown-eyed children were middle children. And I thought (rightly or wrongly) that any marital infidelity would have been more likely later on in the marriage. I wondered about the whole recessive-dominant thing since then.

Modern science over the past few years has supported my appraisal of my grandmothers' virtue. See, for example:

While these studies are not brand new, they're still news for most people. Essentially, eye color is a good bit more complicated than we used to think. While dominant and recessive genes come into play, there is more than one gene involved, and scientists are still uncovering how they work.

Fast forward to today. I have an infant son. And, since Caucasian babies are born with blue eyes, it’s hard to know what he’ll end up with. Looking into the matter has reminded me of how amazingly misunderstood the issue of eye color is. Dr. Sears, a man with many years of baby observing (whatever you think of his approach), says the following in The Baby Book: “When in doubt, I look at the parents. If both parents have brown eyes, guess brown (75 percent chance of being right); if one has brown eyes, still guess brown (fifty percent right); if both blue, guess blue (but baby may still turn out brown-eyed).” Sounds deceptively simple…’til you get to that last sentence.

Recently, I was speaking to a friend who is finishing up medical school with a specialty in pediatric genetic diseases. I told her I’d be really interested in a book on genetics for the layperson. So much has happened in the field in the past decades that I would love something to give me the big picture without the misinformation I got back in 3rd grade. When I explained the origin of my interest and the eye color problem, she looked genuinely surprised to hear that I saw the recessive-dominant model for eye color as wrong. When you think about it, it shouldn’t really be all that surprising, since the standard model doesn’t even take other colors (hazel, green, etc.) into consideration.

I knew those scientists would come around sooner or later...

Oh, and it looks like my baby will have his daddy's baby blues...


  1. DR. RC,

    Interesting, but does it really matter?


  2. Good question--why should anyone care? I'll tell you why I think the issue matters (rather than eye color...). It's because it's an area where Science (or our reduced, myopic understanding of science) Tells Us things that a) are not true and b) we could probably realize aren't true from paying attention to our own experience. The eye color thing is a relatively harmless category, yet it had me wondering if my grandmothers had been unfaithful--with no other evidence than that of my parents' eyes! And even though this simplistic understanding of eye color is clearly wrong, it marches on in textbooks and the like. Which really makes me wonder about "scientific" categories that are more ideologically loaded.