Something I have been wondering for a while is looking at cancer from an evolutionary standpoint.
It's easy to conclude (from observations today) that cancer is something we would rather avoid. However I kept asking myself what would be the purpose of cancer existing in the first place? In my experience of studying biology if a organism or mechanism in nature exists it is because there was a pressure to create it.
It has led me to think that perhaps early on, when cells were just beginning to clump together forming very very primitive organisms, that cancer was a way for a cell to proliferate very quickly and make their particular genomic sequence more common within what would have been organisms made of a lump of cells. Perhaps the different organs we have today exist not just because there was environmental pressure to have a specific organ with a specific function. Perhaps the cells descended from a "cancer" that proliferated faster over other cells in a primitive ancestor of that organism.
The answer that "cancer exists because our bodies make mistakes" doesn't satisfy me when everything else around us evolved and formed due to a multitude of different pressures.
In an effort to make this question less broad my question is basically this:
Is it plausible that cancer is a phenomenon that began to occur relatively early in Earth's evolutionary history as a form of survival for cells in primitive organisms or am I applying evolutionary theory incorrectly?
(I know there is a better word for "pressure" to describe the variables that guide evolution but right now my brain can't come up with anything better).