Veggie Family Secret: Tomatoes are Double First Cousins

Do you know what a penny looks like?

Yeah, I thought I did too. I mean, who doesn’t? The penny is the most common coin in circulation. The U.S. Mint stamps out over 20 million a day. Collectively, we own trillions. I have a fistful of them right now, rattling around at the bottom of my backpack. Penny. Duh.

But don’t jump on this one too fast. A classic experiment of 1979 showed that we’re all perfect morons when it comes to pennies.

The experimental subjects—twenty about-to-be humiliated American adults—were asked to sketch a penny, front and back, and then were scored for their inclusion (or not) of eight crucial penny features. Among these were Head (whose?) and Tail (what?), and the correct locations of such government-sanctioned penny verbiage as IN GOD WE TRUST, E PLURIBUS UNUM, UNITED STATES OF AMERICA, and ONE CENT.

Of the eight, most people got no more than three right. The only thing the majority agreed upon was the Head—Abraham Lincoln—but even so, half of them drew him facing in the wrong direction. In an even more crushing follow-up, when shown pictures of pennies (one genuine, fourteen fake), less than half of the test subjects were able to pick the real penny out of the counterfeit crowd. It’s clear that when it comes to pennies, we shouldn’t be making any foolish bets in bars.

The one exception to the rule—the sole person who got absolutely everything about the penny right, from the knot on Lincoln’s cravat to the elusive position of the word LIBERTY—was a penny collector.

Our Super-Efficient Brains

The researchers behind the experiment were studying a memory phenomenon called perceptual filtering, which is the reason that we can recognize something perfectly well without remembering any picky details. Brains don’t waste energy on non-essentials: for the most part we remember just enough—yup, looks like a penny—to comfortably get by. We filter out the rest, which means that we don’t pay any attention to it. In other words, nobody really knows what a penny looks like.

Unless, as in the case of the penny collector, pennies happen to be our life’s obsession. So the natural question is: since penny anatomy so obviously makes no never mind to most of us, who cares?

It’s a good point. But those pennies made me think about Charles Rick and tomatoes.

What Does a Tomato Really Look Like?

Charles—Charley—Rick was born in 1915 in Reading, Pennsylvania, where he grew up camping with the Boy Scouts and working in the family peach orchard. He got a Ph.D. in plant genetics from Harvard in 1940 and then moved to California, where he had a brief scientific flirtation with spiderwort plants and asparagus. Then he fell in love with tomatoes.

By the time he died in 2002 at the age of 87, he was a legendary tomato collector and the world’s foremost authority on tomato genetics and evolution. Today the C.M. Rick Tomato Genetics Resource Center at UC Davis—a vast gene bank of tomato varieties—is named after him.

So…what does a tomato look like?

Most of us can pick a tomato out of the crowd. No matter what their size, color, or shape—cherry, plum, paste, pear, or beefsteak; tiny or humongous; lobed or round; red, orange, yellow, green, pink, or purple—we can generally identify a tomato. As it turns out, however, there’s more to a tomato than its creative cover. To really know what a tomato looks like, you’ve got to take a closer look.

Down at the level of DNA, where it counts, tomatoes aren’t as varied as they seem. If not exactly identical twins, they’re all at least double first cousins. Researchers guess that cultivated tomatoes collectively contain less than 5 percent of the DNA that’s available in the greater tomato gene pool. From a genetic perspective, what cultivated tomatoes look like is pretty much all the same.

Lack of Genetic Diversity Could Spell Disaster for Tomato

Countless chilling examples—the 19th—century Irish potato famine, for example—have shown us how dangerous it is to put all our horticultural eggs in one genetic basket. Uniform crops topple like dominoes when the right blight comes along. There’s a good reason that nature likes biodiversity.

Charley Rick spent much of his long career traveling through Central and South America—stomping ground of the ancestral tomato—collecting wild tomato species. From these previously ignored wild plants—weedy unpleasant-looking specimens that most of us would never have recognized as a tomato—Rick and colleagues isolated dozens of new and valuable genes capable of beefing up the feeble tame-tomato bloodline.

Rick’s feisty feral tomatoes have given homegrown varieties resistance to a raft of menacing pathogens—nasty stuff like stem canker, fusarium wilt, nematodes, and tobacco (also tomato) mosaic virus. They’ve provided cultivated tomatoes with extra doses of such nutritional tomato bennies as lycopene, beta-carotene, and vitamin C. And wild tomatoes have genes that allow tomatoes to survive where no cultivated tomato has gone before: in cold, hot, dry, dripping, and salty conditions, all of which may be our future lot, given the state of the planetary climate.

Charley Rick, Savior of Spaghetti Sauce

Charley Rick spent 62 years studying tomatoes and to a lot of people that sounds pretty lame. But because of Charley Rick’s tomato collection, I feel a whole lot better about the tomato’s chances for the future. I’d sure hate to lose tomatoes. Tomatoes are America’s favorite garden vegetable. One of the few things I can cook is spaghetti sauce.

It’s popular these days to make fun of scientists. You have only to look at them. They’re weird little people who wear thick glasses. You know—like Beaker, the strange squeaky Muppet. And their behavior, of course, doesn’t help. Look at the way they potter around studying silly-sounding stuff like bread mold and sea slugs and fruit flies.

At least it sounds silly until it suddenly cures diseases, cracks the genetic code, or gets us to the moon. The thing is that great gains often come from what look like small obsessions.

Like knowing what a tomato really looks like.

A version of this essay appeared in the Spring 2012 issue of GreenPrints magazine.

Do you know what a penny looks like? Check out the Penny Memory Test.

This story is part of National Geographic’s special eight-month Future of Food series.