Why is stem cell research controversial?
The short answer is that embryonic stem cell research relies on cloning and/or killing embryonic human beings.
But it is very important to know that not all stem cell research is controversial. In fact, most stem cell research is not. Over the last few years scientists have used what are known as "adult stem cells" to treat or cure 65 different illnesses in human patients. This adult stem cell research typically uses a patient's own stem cells for treatment. (http://www.stemcellresearch.org/facts/treatments.htm)
However, embryonic stem cell research requires the destruction of embryonic human life - that is living, human embryos. To obtain embryonic stem cells a human embryo is encouraged to grow for 5-7 days until the embryo develops stem cells. The stem cells are then extracted from the embryo and the embryo is killed. Each human being begins his or her life as a human embryo. To say "embryo" is not unlike saying fetus, infant, toddler, child, adolescent, and adult. It is an important stage of human development, the beginning stage of development of each human being.
Langman’s Medical Embryology textbook used at many Universities, including the University of Kentucky defines the beginning of human life thus:
"The development of a human begins with fertilization, a process by which the spermatozoon from the male and the oocyte from the female unite to give rise to a new organism, the zygote."
Sadler, T.W. Langman's Medical Embryology. 7th edition. Baltimore: Williams & Wilkins 1995, p. 3] Another popular embryology textbook, The Developing Human, used by the University of Louisville School of Medicine concurs:
“Zygote. This cell results from the union of an oocyte and a sperm during fertilization. A zygote is the beginning of a new human being (i.e., an embryo).”
[Moore, Keith L. and Persaud, T.V.N. The Developing Human: Clinically Oriented Embryology. 7th edition. Philadelphia: Saunders 2003, p. 2.]
For an expansive list of textbook definitions of when human life begins, click here (http://www.usccb.org/prolife/issues/bioethic/fact298.htm)
