Stem cells are seen by many researchers as having virtually unlimited
application in the treatment and cure of many human diseases and disorders
including Alzheimer's, diabetes, cancer, strokes, etc. Stem cells come in two general
types:
Embryonic stem cells are a primitive type of cell that can be coaxed into developing
into all of the 220 types of cells found in the human body (e.g. blood cells,
heart cells, brain cells, nerve cells, etc). They are derived from human embryos
in a process that causes the death of the embryos.
Adult stem cells bear some similarities to embryonic stem cells.
Research using adult cells has a two decade head start on embryonic stem
cells. Thus, potential treatments have already advanced to human trial
stage. Unfortunately, adult cells are limited in flexibility.
Many pro-lifers believe that human life, in the form of an ovum and
spermatozoon, becomes a human person at the time of fertilization. Thus, killing
an embryo in order to extract its stem cells is a form of homicide. They are
generally opposed to such research. Others disagree. They believe that an embryo
has the potential to develop into a person, but is not a person itself. They
note that an embryo is not sentient; it has no brain, sensory organs, ability to
think, awareness of its surroundings, consciousness, internal organs, arms,
legs, head, etc. They feel that research using stem cells derived from embryos
is ethical.