Why don’t cats have brown eyes? April 26, 2008Posted by ourfriendben in critters, pets, Uncategorized, wit and wisdom.
Tags: blue eyes, brown eyes, cat eyes, eye color, human eyes
Admiring the huge, adorable, clueless, seagreen eyes of our cat Linus the other day, it struck our friend Ben that, of all the cats I’ve ever known or seen (and trust me, I’ve been to my share of cat shows), I’ve never seen one with brown eyes. Orange, amber, yellow, every shade of green, blue, even violet (Liz Taylor, eat your heart out)—yes. But brown? Never.
As you all know from high-school biology, brown is the most common eye color. With very rare exceptions (usually among Huskies and Australian shepherds), dogs have brown eyes, though they range from near-black through chocolate to red-brown like our golden retriever Molly’s beautiful eyes. Cows? Brown. Horses? Brown. Guinea pigs? Brown. A quick chat with our friend Ben’s good friend Google puts the number of humans with brown eyes between 85 and 95%. So what’s the deal with cats?! If you know, please help our friend Ben out here.
Our friend Ben unearthed some fascinating data about human eye color while checking the stats for this. Our friend Ben’s eyes are blue, which as you’ll also recall from those high-school biology lessons is a recessive trait, so it can easily disappear if a more dominant color is present in either parent. But even so, our friend Ben didn’t realize that blue eyes are disappearing from the American scene until I read an article called “Don’t it make your blue eyes brown?” that originally appeared in the Boston Globe in October 2006. This article tracks the relatively abrupt and extremely steep decline in blue eye color in the U.S. over the past century, and gives some compelling reasons why it’s happening. The research was done by, of all things, an epidemiologist, which makes our friend Ben wonder whether I should now consider myself an endangered species or a highly contagious disease. Apparently, the highest percentage of blue eyes in the U.S. can now be found in nursing homes, and within another couple of generations, they may disappear from the scene entirely.
But this was only the beginning of the astonishing things our friend Ben turned up. Thanks to genetics, scientists have determined that all blue-eyed people are descended from a single ancestor who lived between 6,000 and 10,000 years ago. Before the genetic mutation that gave him blue eyes, apparently all human eyes were brown. If you have blue eyes today, you also have this genetic mutation. Wow. In the millions of years of human history, 6,000 years seems like an eyeblink (if you’ll pardon the expression in this context). The authors of the study pointed out that blue eyes are as (relatively) common as they are today because the mutation was apparently a hit. By mediaeval times, blue eyes were considered a sign of beauty and fertility, and blue-eyed women were the most sought-after. Blue eyes had become a reproductive advantage.
And that’s not all. Scientists have found that, even today, blue-eyed men prefer blue-eyed women over all others, finding them far more attractive. Studies have shown this to be true not only in the abstract, where the men were asked to select women they found most attractive from a range of faces, but also in real life, where blue-eyed men choose blue-eyed partners much more often than partners with other eye colors. Not only do men with other eye colors not factor eye color into their choices, but blue-eyed women are also colorblind when it comes to choosing partners based on eye color: It isn’t a factor.
Our friend Ben would have simply thought these findings were somewhat curious had I not read on. You see, it’s been our friend Ben’s observation that people in general do tend to find people who look most like them to be most attractive. (Whether this springs from cultural conditioning or simple narcissism, I couldn’t say.) But the authors of this study threw a pitcher of very cold water on our friend Ben’s theory. They concluded that blue-eyed men preferred blue-eyed women because then they could determine their children’s paternity. That is to say, if a child born to a blue-eyed couple did not have blue eyes, then the husband was not the child’s biological father. So marrying blue-eyed women would give blue-eyed men a reproductive advantage in the Darwinian sense. (Of course, the men wouldn’t consciously be aware that this genetic imperative was driving their choice of mates.)
This was all very interesting, but it wasn’t the end of our friend Ben’s discoveries. Yet another article posited that blue-eyed people were considered especially attractive because pale irises allowed others to easily see when one was experiencing pleasure or excitement (in both cases, the pupil dilates). Because these are considered attractive and desirable states (remember those unfortunate women in Regency England who put laudanum drops in their eyes to enlarge their pupils and make themselves more attractive?), being able to see them confers desirability on the person whose eyes are, literally, telling all.
Our friend Ben was reminded of a conversation with a friend in grad school who claimed that he could never tell what our friend Ben was thinking because of my blue eyes. But of course our friend Ben found it much easier to “read” blue and green eyes than the dark eyes of my friend, and a lively debate ensued. In light of all this, our friend Ben would like to dispense a bit of advice: If you have blue eyes, remember that you may be giving away more of your feelings than you think. And if you have dark eyes, you may need to be a bit more demonstrative to let people know how you’re feeling.
One last thing: Blue eyes are not the rarest color. Green eyes are! Only 1 to 3% of the world population has green eyes, and as you’d expect, most of them live in Ireland, where the percentage jumps to 20%. But our friend Ben would bet that in the cat world, green is the dominant hue. It certainly is around here!