If I got a nickel every time someone died of cancer, I'd be rich. And probably have a massive guilt complex.
If someone dies because of cancer, you're never sure about the real reason. If used wrong, quite everything may provoke cancer... we all are continuously exposed to so many dangerous things.
There isn't even a simple answer to what cancer really is -- it's more the description of a symptom, and not the real cause...
In contrast, religion could (in these terms) be characterized as a process in which someone has a revelation and tries to pass it on, it gradually becomes distorted through transmission, and there are recurring attempts to return to the original vision.
I completely agree: but sometimes you have to wait centuries for this to happen...
A far more important case is the effects of low levels of radiation on cancer. It's been assumed my some people that there is a linear relationship between the risk of cancer and total radiation but there is still a lot of debate on the topic.
In both cased their are competing ideas, but the entrenched idea is just older and unlike evolution or the general theory of relativity it's far from accepted as correct.
For the last 4 centuries, we have seen a continuous increase of science to form peoples' opinion.
But science is only science (no joke -- it's the current opinion of most scientists).
So, peoples' opinion and science are deeply related.
One of them seems to be real science, the other is more similar to religion than to real science.
The most important fact is: only the scientific one is full of adverse effects...
The one that has doubled the world average life expectancy over the last century.
Are you referring to the life expectancy for 20-year-olds?
[Edit: I found some data here: http://www.cdc.gov/nchs/fastats/lifexpec.htm http://www.cdc.gov/nchs/data/nvsr/nvsr56/nvsr56_09.pdf 20-year-olds do seem to have benefited quite a bit in the first half of the 20th century. I had assumed that life-expectancy was virtually unchanged across the century, except for that of infants and other under-five-year-olds.]
Life expectancy has been more or less like nowadays in past, and this for a long time.
Then came the Industrial Revolution (a product of modern science), and it went down to half. Then came modern medicine, and tried to bring it back to where it had already been for a long, long time...
If you look at other people, you see that there have been periods where people lived 100 years and more, and this many many centuries back.
Regarding science and religion: don't you know that the european scientists in past have all been christians? So, science and religion are not opposed to each other, as many modern people think: this is only a recent invention.