How cancer starts in the body?
In: Biology
A slightly different perspective is to imagine cancer from an evolutionary point of view.
Single-celled life began really soon after liquid water appeared on Earth, perhaps only a few 100 million years. It stayed single-cell for the next THREE BILLION YEARS, and only went multicellular about 600 million years ago.
Why did it take so long (really, it was amazingly long, 5x longer than the whole history of all multicellular life!) for the first complex organisms to appear?
In single-celled organisms, it’s every cell for itself. But in a multicellular creature, each cell has to be prepared to die for the health of the whole animal. It’s prepared to die because it knows that every other cell in the creature has the same DNA, so personal death doesn’t matter.
This “multicellular contract” has a range of biological mechanisms underpinning it. These mechanisms look for cells that are not quite right, perhaps because of a DNA change due to a random mutation, and quickly kills them. You can imagine every cell in your body having a large red button on its back with “KILL ME NOW” written on it. Patrol cells wander around your body looking for suspicious behaviour, and if they see a cell acting out, they’ll push that button.
This is why multicellular life took so long to appear — these mechanisms are the exact opposite of what single-celled creatures are trying to do: multiply as rapidly as possible and hang the consequences.
We humans have around 7 separate mechanisms like this, all aiming to exterminate cells which go rogue. When, without being detected, a cell accumulates enough mutations to let it evade all 7 regulation mechanisms, it can go crazy, reproduce like mad, and our bodies can’t stop it. The multicellular contract collapses, 3 billion years of evolution unwind, and your cells start acting like unicellular organisms again. This is cancer.
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