One thing which I always thought of, but which the article doesn't mention, is age. Especially older people seem more prone to cancer, so in my mind a lower life expectancy will naturally lead to a lower cancer rate, as people die before cancer "is able to get them". Or am I missing something?
This is a common misconception. Life expectancy hasn't changed much. It's children dying that bright down the average in earlier years. If you lived to your 20s your life expectancy was pretty much the same as it is now.
It's 82 today.
The effects are not as dramatic as when infant mortality is included but our life expectancy has absolutely increased.
It's a compelling theory, too, because the average age of a cancer is 66 today. But it really addresses the idea of cancer being less prevalent than less likely.