Magic embryology: rapid stem cell differentiation (Introduction)

by David Turell , Wednesday, April 22, 2020, 23:22 (1463 days ago) @ dhw

DAVID: Correction. Stem cells are programmed to be exact copiers, not evolvers. That job is in the germ cells DNA to carry over new changes, but we do not know exactly how it works for new species.

dhw: According to my science dictionary, the stem cell is “an undifferentiated cell, particularly in an embryo, capable of unlimited division and of producing daughter cells that develop into different cell types, which in turn give rise to different tissues and organs.” How this comes to mean that they are “exact copiers” I really don’t know, and a cell that can give rise to different tissues and organs sounds to me like the perfect foundation for evolution.

DAVID: Your dictionary is correct. The stem cells follow what instructions the germ cells give in their DNA. The are bound by those instructions to exactly reproduce what came before: horse makes horse, fox makes fox, robin makes robin. An unwanted mutation in an embryo stem cell can create a monster.

dhw: Obviously, but the definition tells us that stem cells can produce cells which give rise to different tissues and organs, and the article you quoted says: "Our biological history can be traced back to a small group of cells called embryonic stem cells, which through cell division, give rise to cells that specialise to perform a specific role in the body—a process known as differentiation.” I’ve also read that stem cells are used in various treatments to repair defects, as they can adopt different “identities”. If our whole history can be traced back to stem cells, which are capable of giving rise to different organs, doesn’t that suggest that they provide the foundations for evolution? I’m asking, not telling. You are the scientist.

You are trying to stretch a definition. Stick with my quote above. The zygote, formed from the junction of sperm and egg carry all the genome instructions and stem cells follow the definitive rules.