Imagine the surprise among Greeks in about 400 B.C., when Hippocrates began to teach that diseases are natural, not supernatural; or in 1543, when Andreas Vesalius published a book on human anatomy based on what he had observed.

William Harvey shook the world with his ideas about the circulation of blood in 1628. And about 1796, Edward Jenner discovered a way to vaccinate people against the deadly scourge smallpox.

Louis Pasteur did his remarkable work on bacteria in the 1870s. And only 50 or so years later, Alexander Fleming discovered penicillin. The world marveled at medical research again in 1955, when Jonas Salk’s vaccine against polio was released to the world.

For centuries, people have faced the march of scientific research and have asked the obvious question. Where does man draw the line? Organ transplants, artificial hearts, re-attached limbs – and now, cloning of human embryos. As possible benefits of the technology boggle the mind, the questions will tweak our souls.

Scientists with Advanced Cell Technology announced earlier this week that they had successfully cloned human embryos. They hastened to say the company’s purpose is to produce genetically matched replacement cells for patients with a wide range of diseases and disabilities – not to reproduce people.

Reactions to the news were easy to predict. Daisy the sheep, the first cloned mammal, gave us pause, maybe even the creeps. Still, once the science became real and not science fiction, we knew what would follow. And it has.

The division between opponents and proponents of cloning human embryos is not a clear one. The science is exciting, doctors say. The promise is magnificent, say those whose lives are skewed, out of whack because of injuries or disease.

It is easy to imagine the joy and anticipation felt by someone such as Christopher Reeve, victim of one of the most highly profiled spinal injuries in our lifetimes. Using his celebrity, he has been a wheelchair-bound advocate for stem cell research that might one day lead to cures for the lame.

Cures – let’s say it, miracles – of enormous proportion lie in the tiny blobs that researchers say will fit on the head of a pin. From the success with these small pools of cells may come organ transplants that a body won’t reject; regrowth of bodily tissue, maybe even entire organs or limbs someday, and cures for diseases such as diabetes.

All of science in its colorful and storied history has run headlong into religious, moral and ethical resistance. Theories about the origins of the universe, the creation of man and the possibility of life in other parts of the universe long have prompted debate.

One advantage of this generation may be an ability to put a light touch on even the most serious of issues. The Rev. Dale Little of the Adams Baptist Union Association tells this story:

God and a lab scientist were talking. They decided each would make a man. The scientist said he would go first, and he reached for a handful of dirt. God said, “No, no! Get your own dirt.”

No inquisition is planned as a result of the embryo cloning, no stoning in the town square, no witch hunt. Still, the debate will be passionate, always the case when ground-breaking science takes our breath away – or gives it back.

Joan Gandy is special projects director of The Democrat. She can be reached at (601) 445-3549 or by e-mail to joan.gandy@natchezdemocrat.com.