A science writer I like very much, Matt Ridley, summarizes the evidence for a controversial theory that AIDS was caused when thousands of Africans were given a live polio vaccine grown on chimpanzee kidney tissue in the ’50’s. “(A) particular type of live polio vaccine called Chat may have been grown in the 1950s in cells

derived from chimpanzee kidneys. Chimpanzees are the probable animal source of the AIDS virus; live

vaccines could have been contaminated if an infected animal was used. Chat was tested on more than 1 million Africans in 1957-60, in the very areas where AIDS subsequently became epidemic for the first time.

Two other, less serious forms of AIDS developed in parts of west Africa at about the same time, each epidemic closely associated with an

area in which similar live polio vaccines may have been tested.

Stated thus, the theory seems purely circumstantial. It boils down to seven assertions, all of which must be tested to destruction….”