Is there a purpose to a cancer cell?
In: Biology
In addition to the already posted replies, you might be wondering why, if cancer is just our own cells being jerks, why it exists if it seems to harm us and doesn’t provide any benefit.
First, you have to consider the circumstances under which we evolved. People often didn’t live long enough for cancer to a reason for death. Now that it’s much more common to live longer, it’s much more common for cancer to be a cause of death. (Same with teeth. I’ll never forget overhearing my dentist coming out of an elderly patient’s room saying to his assistant, “Fuck. Teeth just weren’t made to last 80 years.”) So, if cancer doesn’t have much effect on our reproductive success it won’t be selected against very strongly. Pretend there’s a “kidney cancer at age 70 gene” and a “brain cancer at age 5 gene”. The kidney cancer gene can easily be passed down to offspring while the brain cancer gene won’t be.
What about cancers that DO affect young people? Well, whatever circumstances (genes, hormones, etc.) allow for cancer most likely have an overall beneficial effect. You’ve probably heard of the famous example of sickle cell anemia. It’s a heritable disease common among people whose ancestors lived in areas where malaria was common. The same genes which cause sickle cell anemia also provide some defense against malaria. Since it is (or was), on balance, a net positive for that population of humans, it survived.
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