All in the Family

Rough Draft
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By Joel Achenbach
Sunday, December 10, 2006

One day recently, my phone rang with a news tip from a trusted source at a science organization. "There's a paper coming out next week that you might find interesting," she said. I held my breath and thought of the obvious possibilities (Earth is hollow, dolphins chirp palindromically, astronomers discover fruitcake at center of galaxy), but my source hit me with something unexpected:

"They've sequenced the sea urchin genome."

Ah. Right. About damned time, too. I knew I would write about this, because you never want to pass up an opportunity to use the excellent word "urchin." A columnist has to use as many good words as possible, such as "ungulate," "scabrous," "thwap!" (sound effect), "gnomic," "mephitic," "prelapsarian," "antediluvian" (but not in the same sentence as "prelapsarian"), "skeezy" and (not for the amateur) "farraginous."

I called a couple of the scientists who did the sea urchin research, and learned, first and foremost, what a sea urchin is. It's one of those spiky things you see on coral reefs. With all due respect, it's a brainless, eyeless, plodding creature that moves about with the help of little "tube feet." But it's also a highly successful organism. A sea urchin can live to be 100 years old.

Laboratory scientists love sea urchins. They reproduce by squirting eggs and sperm into the water (the sea urchins, I'm talking about), and letting them find one another in the great singles bar of the shallow sea. No womb necessary. Scientists can therefore replicate the process in a petri dish, and sea urchin embryos have told us much about how a fertilized egg turns into a complex organism.

For a long time we've known that these creatures initially develop very much like human beings. We're more like sea urchins than we're like dragonflies or spiders.

"A human being is a chordate. The sea urchin is in the larger group called the echinoderms. The chordates and the echinoderms are what you call deuterostomes," explained Erica Sodergren, a molecular biologist at Baylor College of Medicine. "That just means when they are developing they get a mouth, and they get an anus, and their gut develops. Protostomes have a different way those holes develop."

There will not be a test. The point is that we have close cousins and distant cousins, and sea urchins are medium-distant cousins. What surprised scientists when they finished the sea urchin project is that we have so many genetic similarities.

"Many, many of the genes in sea urchins are the same as genes in humans," said George Weinstock, a biologist at Baylor, who, like Sodergren, is a lead author of the new paper in the journal Science.

For example, a protein critical to human sight (a gene is the genetic code for the making of a protein) can be found in the sea urchin's tube feet. Weinstock's sound bite: "Sea urchins see with their feet."

Another example: A protein involved in human hearing is found in sea urchin spines. Perhaps our ability to make sense of vibrations in the air -- to hear -- is related to the sea urchins' ability to detect ocean currents.

The point here isn't that humans are similar to sea urchins. We're radically different creatures. The big revelation is that evolution is highly conservative. When it makes something new, it employs the familiar stuff already lying around.

Consider that we parted ways -- the urchins and humans -- about 500 million years ago. We've headed down wildly divergent paths, one leading to the coral reef, the other to the office cubicle. But we're both built of pretty much the same off-the-shelf material -- just tweaked a bit.

Weinstock said, "After millions of years of evolution, the things we have are the things that have survived very extensive testing. These are the things that work very well. And you just tinker with that."

They won't say it, because it's grandiose, but these scientists have discovered one of the basic secrets of life. And let's extrapolate further: We often imagine that doing something new and extraordinary would require that we change radically in some way. We think we'd need a new job, new residence, new religion or, in my case, a brain transplant. But you can do almost anything with what you already have. Evolution shows the way.

This has inspired me so much that I vow here and now to be a better deuterostome.

Read Joel Achenbach weekdays at washingtonpost.com/achenblog.


© 2006 The Washington Post Company

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