The three high school friends stood together at a table, goggles protecting their eyes and putty knives in hand, as they delicately split a block of ancient earth in search of fish fossils that scientists said were 10 million years old.

Emily Howell, 17, a Gaithersburg High School senior, said she didn't believe the scientists because, to her, nothing on Earth is more than 6,000 years old, and Charles Darwin's theory that living things have evolved from a common ancestry over eons is a myth.

Her classmate, Emily Myron, also a 17-year-old senior, said she respects her friend but "believes in evolution wholeheartedly" because there is "far too much evidence" to deny it.

At her side was lifelong friend Katie Zdilla, 17, a Sherwood High School senior who said she wasn't sure of the age of the 21/2-inch stickleback fish fossil the girls found by separating layers of crumbly, dusty diatomaceous earth. She believes, she said, in some parts of evolution and not others but certainly that God was responsible for everything.

The students were attending a two-day conference on evolution at the Howard Hughes Medical Institute in Chevy Chase at a time when polls show that at least half of Americans doubt Darwin's theory of evolution. That has made the teaching of evolution one of the most contested issues facing educators.

The conference drew 175 high school students from public and private schools throughout the Washington area, all selected by their schools for their scientific achievement -- if not for their personal beliefs in evolution. It was the 13th in the institute's annual Holiday Lectures series on scientific topics for students and was simultaneously webcast to more than 300 sites, including schools, around the world. (The institute makes DVDs of the lectures and distributes them free to teachers.)

The vast majority of scientists say that evolution is a proven concept in biology and oppose evolution challenges -- including those led by advocates of "intelligent design," a hypothesis that some aspects of evolution were caused by an intelligent designer, not by random mutation and natural selection.

The debate "has been disconcerting to the scientific community," Sean B. Carroll, a Hughes institute investigator at the University of Wisconsin at Madison, told the participants. For one thing, he said, evolution's challengers cannot scientifically test their thinking. He also blamed media outlets for trying to give equal weight to concepts -- evolution and creationism -- that he said were not equal in evidence or construct, thus furthering confusion.

The institute is a nonprofit medical research organization that operates what it says is the largest privately funded science education initiative in the United States. Students at the conference heard four lectures about evolution from Carroll and Prof. David M. Kingsley of Stanford University's School of Medicine; looked for fossils; and participated in a 90-minute discussion on evolution and religion.

The Rev. James Wiseman, former abbot of St. Anselm's Monastery in Northeast Washington, told the students that Catholics believe there is no conflict between God's supremacy and Darwinian evolution.

Philosopher Michael Ruse of Florida State University, who declared himself an ardent Darwinist, elicited laughter from the crowd when a student asked whether creationism and evolution were different paths to the same truth. Said Ruse: "No. All ideas aren't equal. Some ideas are better than others." (He also said that if Darwin were alive, Carroll would be the person with whom he would choose to dine.)

Many of the conference participants said the material broadened what they had learned in biology classes about how nature selects members of a species with mutations best suited for a particular environment. They expressed delight at details of Darwin's life that they said humanized the stern, bearded face in textbooks.

"He played backgammon every night with his wife," said Rebecca Vogel, 16, a junior at Montgomery Blair High School in Silver Spring.

"He had a queasy stomach and dropped out of medical school," said her classmate Rose Feinberg, a 17-year-old senior.

Some, particularly public school students, said it was clear that the ongoing debate over evolution was having a direct impact on what and how they learn. They said some teachers seem fearful of stoking controversy. And Luke Chang, 15, a junior at Montgomery Blair, said he believes his teacher brings up the issue of intelligent design, even briefly, to be "politically correct."

Howell and Myron said they knew that their Advanced Placement biology teacher at Gaithersburg High, Kurt Richter, is a strong believer in evolution but that he would let them make up their minds.

Richter said that he makes a strong effort to present evidence and not opinions -- and that the approach works in educating students, more than half of whom enter his science classes disbelieving evolution. Most change their minds.

Not Howell, however, who said she took Advanced Placement Biology with Richter last year and kept telling him that she had a "different worldview" from her teacher, one based on a literal reading of the Bible. Nothing would shake it.

Richter said that she was an excellent student and deserved a chance to attend the evolution conference.

The highlight of the two days at the institute for many students was the hunt for fossils in a heated tent where about 1,500 pounds of earth from the Southwest sat in clumps on tables, waiting to be excavated. Prof. Michael A. Bell from the State University of New York at Stony Brook helped students decked out in protective gear find and identify fossils, although identification was not always easy.

Laetitia N'dri, a 16-year-old junior from Connelly School of the Holy Child in Potomac, found a discoloration on the white earth and asked hopefully what it was. Most likely fossil fish feces, Bell said.

At another table, Howell, Myron and Zdilla found a fossil that looked remarkably similar to the feces fossil, but Bell said it most likely was a 10-million-year-old fossil of fish regurgitation. It takes an expert to tell the difference.

In the end, many students said they left with new knowledge about evolution.

As for beliefs: Howell, Myron and Zdilla said nothing had changed.

Prof. Michael A. Bell from the State University of New York at Stony Brook tells students at a two-day conference on evolution how to find and identify fossils.High school seniors Nidhi Tewari, left, and Harleen Bath, along with Jina Yoo, a junior, try to separate layers of diatomaceous earth in search of fish fossils.