Meaning of life is thorny question

Later this century, the definition of life will be at the heart of a political and societal debate as heated and divisive as abortion and embryonic stem cell research, Caplan predicts.

Look for changes in religion too.

"As knowledge has [been] added, religions have adapted," Venter said. "I don't see why this is any different. We're pushing the frontiers of knowledge, understanding life on this planet."

Venter dismisses suggestions that scientists are playing God as media sensationalism. And Collins, a scientist who talks at length about his faith, said he found it interesting that the people who most often use the phrase "playing God" usually didn't believe in God.

"Playing God" is a secular, not religious, term, said Ted Peters, a professor at the Graduate Theological Union in Berkeley, Calif., and author of the book "Playing God." He said people who worried about that were really talking about tinkering with nature.

"What Craig Venter is doing is an extremely complicated form of animal breeding," Peters said. "We're going to be changing the face of the planet no matter what. The question is, do we want to do it responsibly or not?"

C. Ben Mitchell, a bioethicist connected with Trinity University, an evangelical Christian college in Illinois, worries about entrusting such monumental developments with scientists.

"Human history is enough; it is sufficient to remind us of the problem of hubris," Mitchell said. "It is at least a cautionary note, to caution us to be aware of unintended consequences."

One of the men trying to make life from scratch, Mark Bedau, understands the worries. A philosophy professor from Reed College in Oregon, Bedau is also the chief operating officer of the synthetic biology firm ProtoLife in Venice, Italy.

His team and others are trying to make single-cell organisms from chemical components, creating a genetic system that multiplies and a metabolism that takes in energy from the environment. Scientists say they are close to completing a key first step, creation of a vesicle, or container, for the cell.

"We are doing things which were thought to be the province, in some quarters, of God -- like making new forms of life," Bedau said in a phone interview from Venice. "Life is very powerful, and if we can get it to do what we want . . . there are all kinds of good things that can be done.

"Playing God is a good thing to do as long as you're doing it responsibly," he said.