VATICAN CITY Pope Benedict said on Thursday that embryonic stem cell research, artificial insemination and the prospect of human cloning had "shattered" human dignity.
In an address to members of the Vatican department on doctrinal matters, Benedict said the Church had a duty to defend the "great values at stake" in the field of bioethics.
The speech was the latest in a series in which the conservative Pope has told his listeners that scientific progress should not be accepted uncritically.
Benedict, who headed the same department for years before his election in 2005, said the Church was not against scientific progress but wanted it based on "ethical-moral principles".
He said this included total respect for the human being as a person "from conception until natural death," and respect for the natural transmission of life through sexual intercourse.
Practices like freezing embryos, suppression of embryos in multiple pregnancies, embryonic stem cell research, the prospect of human cloning and artificial insemination outside the body had "shattered the barriers meant to protect human dignity", he said.
"When human beings in the weakest and most defenseless state of their existence are selected, abandoned, killed or used as pure 'biological material,' how can one deny that they are being treated not as 'someone' but as 'something,'" he said.
Such practices "questioned the very concept of the dignity of man," he said in the speech to the department known as the Congregation for the Doctrine of the Faith.
Widespread interest in medicine by the general public, who get most of their information from the media, had made it even more imperative for the Church to take a stand, he said.
Embryonic stem cell research involves the destruction of embryos. Scientists hope to use stem cells to transform medicine, providing regenerative treatments for injuries and seeking new insights into diseases like cancer and AIDS.
Last year scientists reported they had tricked ordinary skin cells into behaving like embryonic stem cells.
The Pope said the Church "appreciates and encourages" research on stem cells that come from other parts of the body and do not involve embryos or their destruction.
He rejected accusations from critics who say the Church is an obstacle to science and human progress, saying growing concern about cloning and other practices showed it was right to raise the alarm.
It was the Pope's latest foray into scientific issues. On Monday he warned against the "seductive" powers of science, saying it was important that science did not become the sole criteria for goodness.
U.S. Cardinal William Levada, Benedict's successor as head of the doctrinal department, said it was mulling the possibility of preparing a new Vatican document on bioethical issues.
(Editing by Michael Winfrey)