For decades, belief in evolution has skewed along faith lines, with evangelical Christians as doubters on one side and agnostics and atheists as believers on the other. Now, according to a poll released by the Pew Research Center, the divide is skewed by politics as well. Republicans have become significantly less likely than Democrats to believe in evolution (43 percent vs. 67 percent). Just what we need: the thoughtfulness and delicacy of polarized politics added to the rancor already present.

I've been talking to people on both sides while publicizing a book, The Adam Quest: Eleven Scientists Who Held on to a Strong Faith While Wrestling With the Mystery of Human Origins. I'm struck, in these conversations, that neither side can believe that any thinking person could possibly believe what the other claims to believe. For them, their opponents' ideas for or against evolution must be a product of some form of hysteria or myopia or some conspiracy to either maintain a medieval worldview or destroy religion.

I don't mean to make light of the convictions on either side. Both sets of people are passionately dedicated to the truth, one through the truthfulness of the sacred Scriptures of Judaism and Christianity, the other through the truthfulness of the dedicated, ethical process we call science. The problem is that we've reached a point of no communication, just bomb throwing across the barricade. It's bad, and it's getting worse.

It's bad for science, because it undermines science education (and career choices) for a significant proportion of our young people. It's bad because scientific funding and support get caught up in political quarrels that have absolutely nothing to do with science. Perhaps most significantly, it's bad because it reinforces temptations scientists have always felt to believe that they already know everything important, that non-scientists have nothing to add to the world's fund of wisdom. Science can be arrogant -- dangerously so -- nd polarization encourages it.

It's bad for faith, too, which regularly goes off the rails when it thinks that it has all the answers and that those who see the world differently are infidels and fools. It's bad because it drives away young people. (Evangelical pollster David Kinnaman found that the church's anti-science reputation is a major reason that young people reject church.) It's bad because it puts people of faith in the unhealthy position of relying on science every day (using cellphones, for example) while simultaneously regarding science with grave suspicion.

It's bad for Republicans, who find their "brand" linked to an image of medieval obscurantism. Americans have been, since 1776, a thoroughly modern people determined to live in the future. You don't want to build a party on a slogan of "back to the past."

It's bad for Democrats, who find their "brand" linked to an image of faithless materialism. Americans have been, for just as long, a religious people deeply suspicious of faith's cultured despisers. You don't want to build a party on the philosophy of Voltaire. In France, maybe, but not in America.

Most of all, it's bad for our children. Right now, a young person tuning in to these battles over evolution is bound to conclude that he or she has to choose. Either you follow science or you follow faith. You can't do both.

One of the scientists I profile in my book, the well-known paleontologist Mary Schweitzer, teaches at North Carolina State University. She says that many of the undergraduates who take her course, "Dinosaur World," come from conservative churches. "They see the data for evolution, and they are placed in an uncomfortable position, splitting their heads and their hearts. They usually choose to walk away from their faith.

"The best gift I can give my students," she goes on, "is to ask the right questions. I tell them that science is not the only answer. Science can't prove the existence of God or that you love your children. There's so much that we can't touch with science, because science is meant to be measured. You can't measure God."

What do we want for our children? What do people on both sides want for their children? Most people would say that they want their children to be scientifically literate, and to have a chance at a career using science. Most people would say they want to raise children with the best attributes of faith, believing in something more than a purely material existence. Most people want their children to learn respect for other people, even those who are very different from them.

It's possible to have all three. But right now, the way we're carrying on battles over evolution, many of our children will manage only one of these three. They will shy away from science because it demands that they abandon faith. They will avoid faith because it requires forsaking science. And they will have no idea -- in this realm, at least -- that it is possible to disagree with someone on the deepest level and yet treat them with respect.