As long as I've been asked to comment on the conspiracy, here's
some information I have from a friend in the field of epidemiology.
Cigarettes are the fall-guys.  The experements her lab did involved
inserting a cigarette into the throats of animals so that their every
breath was a drag from a cigarette, and they did not get cancer.  What was
shown was that cigarettes improve long term memory and reduce the risk of
colon cancer.  When asked where all the cancer was comming from, she
proposed that it was from asbestos and petrochemicals.  She is a smoker,
but she tests as a non-smoker medically.  (She smoked immediately before
the test, too).
        What does this mean for paleolithic eaters?  They should probably
give up smoking, anyway.  There is good evidence that chewing tabacco does
cause mouth cancer, and we strive to drug ourselves in the absesnce of
technology as sophisticated as a Bic lighter.