The most important thing learned from this experiment is that embryonic development employs similar mechanisms in a wide variety of mammals. This is important for human developmental studies because we now know that what does or doesn t work in a cow will be the same for humans. Developmental experiments can be carried out on other animals and the knowledge can be extrapolated to humans. Ethicists are concerned because human embryos are normally used to obtain human stem cells. It is possible for a single stem cell to become an entire organism, so in essence scientists are keeping people in petri dishes and not allowing them to mature past the blastula stage.
Ethicists are also concerned about a hybrid between a human and a cow.
What is especially troubling is that this cell can grow into a complete person. The benefits of germ line therapy seem limitless. Every year many genes that lead to medical disorders are discovered. Germ line therapy may be able to help cure these diseases in the present population and eradicate it from future generations. Adult body cells are much more abundant than embryonic cells, and no fetuses are sacrificed to make new tissue.