For 5/6 of the history of life, all life was unicellular, and went through the cell cycle on a regular basis. As soon as enough growth had occurred, the cell would begin the "S" phase, eventually leading to mitosis and cell division. Between 600 and 400 million years ago, some eukaryotes became multicellular (animals, plants, fungi). Most of their cells now divide only a limited number of times before pausing in "G1" and specializing. These cells, all formed …showed first 75 words of 1734 total…

…showed last 75 words of 1734 total…five years cancer free". Notes by teacher: It is important to remember that cancer cells are just doing what evolution has programmed into their genes for the last 3.5 billion years. It is not surprising that the "mitotic brakes" that have evolved over the last 600 million years sometimes fail. Only by investing in research will we learn the details of how this failure occurs in specific cells, and how we can prevent or repair the damage.