Do you like Wikipedia? I do. While it's certainly not the last word on anything, it is sometimes a wonderful launching pad for research on just about any subject. Take "embryonic stem cells," for example. (A topic this blog is very interested in.)Here's the Wikipedia lead in to the subject:

Embryonic stem cells (ES cells) are stem cells derived from the inner cell mass of an early stage embryo known as a blastocyst. Human embryos reach the blastocyst stage 4-5 days post fertilization, at which time they consist of 50-150 cells.

ES cells are pluripotent. This means they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm. These include each of the more than 220 cell types in the adult body. Pluripotency distinguishes ES cells from multipotent progenitor cells found in the adult; these only form a limited number of cell types. When given no stimuli for differentiation, (i.e. when grown in vitro), ES cells maintain pluripotency through multiple cell divisions. The presence of pluripotent adult stem cells remains a subject of scientific debate.

One thing I like about Wikipedia is the Table of Contents that divides each topic into sub-categories, many with links of their own. Under Embryonic Stem Cells, one can click on "stem cell controversy" in the second paragraph, which will take you to a separate entry on just that. (Of course the controversy is grounded in differences of opinion on when human life begins.) From the "controversy" entry:

The status of the human embryo and human embryonic stem cell research is a controversial issue as, with the present state of technology, the creation of a human embryonic stem cell line requires the destruction of a human embryo. Stem cell debates have motivated and reinvigorated the ‘pro-life’ movement, whose members are concerned with the rights and status of the embryo as an early-aged human life. They believe that embryonic stem cell research instrumentalizes and violates the sanctity of life and constitutes murder.[1] The fundamental assertion of those who oppose embryonic stem cell research is the belief that human life is inviolable, combined with the opinion that human life begins when a sperm cell fertilizes an egg cell to form a single cell.

Most stem cell researchers use embryos that were created but not used in in vitro fertility treatments to derive new stem cell lines. Most of these embryos are slated to be destroyed, or stored indefinitely. In the United States alone, there have been estimates of at least 400,000 such embryos.[2] This has led some opponents of abortion, such as Senator Orrin Hatch, to support human embryonic stem cell research.[3]

The bracketed numbers are links to the source material for that particular item (and many of the sources cited have links to the source itself). Ah, the wonders of the Web. As long as you remember not to believe everything you read, and to check and re-check the sources, Wikipedia is a great resource for an initial look into a subject.

Labels: beginning of human life, embryo, embryonic stem cell, in vitro, Wikipedia