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Monday, Feb. 19, 2001

NATURAL SELECTIONS

Genome decoded: evolution, religion and what it all means


The publication of the human genome sequence has been compared to the detonation of the first atomic bomb and the landing of the first human on the moon.

But unlike nuclear warheads and lunar landings, the human genome has a weak visual punch -- there are no images of mushroom clouds or astronauts here, only coils of DNA and pages and pages of deciphered code. Some people may be left wondering what the big deal is. Scientists tell us it will revolutionize medicine and unlock the secrets of our genetic heritage -- but what does it really mean? How does that change how we think about ourselves?

Perhaps we should ask religious leaders. After all, they spend their time thinking about what it means to be human: They might be able to articulate how this monumentous event will affect us.

Rabbi Elliot Dorff, professor of philosophy at the University of Judaism, Los Angeles, expressed his "wonder and awe" at the news. "This is clearly an event in which science and religion should be at one in rejoicing, for we know just how much wisdom God demonstrated in making us as we are."

But before we start the street party, let's look at what the genome sequence tells us about God's wisdom.

The most striking aspect of the sequence, published in landmark issues of Science and Nature last week, is that there are vast stretches of "desertlike regions" where there are no genes. Deserts account for a quarter of the genome. A third is comprised of highly repetitive sequences -- parasitic DNA that doesn't code for anything. What's it doing there?

Much has also been made of the finding that there are far fewer genes than expected, between 30,000-40,000. Fruit flies have 13,000 genes. You can almost hear the collective media puffing out its chest in indignation: Why so few genes for us complex humans?

Even weirder, we share 10 percent of our genes with fruit flies and nematode worms. And 223 genes in humans are more similar to bacteria than to anything in the yeast, worm, fly or plant genomes already sequenced. The bacterial genes are also found in other vertebrates, indicating that they were introduced early in vertebrate evolution. Why do we have bacterially inherited genes? Their presence tells us something about evolution by natural selection, but it doesn't say much for God's wisdom.

Ted Peters, professor of systematic theology at the Lutheran Theological Seminary, Berkeley, Calif., agrees with Rabbi Dorff, saying, "The uncovering of the genetic code is a revelation of one of the wondrous ways God has stitched together the fabric of creation." But why are there deserts and parasitic DNA in the fabric? It seems that God needs some needlecraft lessons.

Perhaps it's no wonder that religious leaders resort to vague metaphors when they talk about the genome sequence. It's "a jewel of nature," said Peters. It's a jewel all right, but a flawed one, revealing the marks of evolution. Religious leaders are reacting to the news that humans are not unique. What else can they do but hide behind metaphor?

Even more world-shaking will be the comparison between humans and chimpanzees. We already know they are our closest relatives, sharing about 99 percent of our genes. A chimpanzee genome sequence will now be easy to produce, using the human one as a guide, and it will show that chimp gene content and organization is "very similar, if not identical, to our own," said Svante Paabo of the Max Planck Institute of Evolutionary Anthropology, Leipzig, Germany. The small changes in DNA between our genomes account for the genetic basis of all the differences between us.

"The realization that one or a few genetic accidents made human history possible will provide us with a whole new set of philosophical challenges to think about," said Paabo. It is these philosophical challenges that religious leaders seem reluctant to address, understandably so, for if it shakes our world, imagine what it does to theirs.

Writing in Science, Paabo stresses that the genome is but "an internal scaffold" for our existence. The West, he says, owes such things as science, technology, architecture and democracy to ancient Greece, "yet at best a tiny fraction of the gene pool of the Western industrialized world came from the ancient Greeks." But that doesn't diminish the influence of ancient Greece on the West, and nor will the genome on its own tell us what it means to be human.

Paabo looks to what is now possible. The gene pool in Africa is more diverse than elsewhere, and the genetic variation found outside Africa is only a subset of that found in Africa. "From a genetic perspective, all humans are therefore Africans, either residing in Africa or in recent exile," he said.

Because of this, abuse of genome data for racist purposes should be difficult. "Race, although culturally important, reflects just a few continuous traits determined by a tiny fraction of our genes," said Paabo. And that tiny fraction has no relation to variation at other parts of the genome. "Consequently, stigmatizing any particular group of individuals on the basis of ethnicity or carrier status for certain alleles [genes] will reveal itself as absurd."

When that happens, it'll be time to start the street party.

Email Rowan Hooper at rowhoop@nies.go.jp


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