If you have a Java enabled browser (e.g Netscape Communicator or Internet Explorer 4.0) you should be able to see a graphic example of the tit-for-tat strategy becoming more widespread over generations when competing with other strategies, including a suspicious tit-for-tat by clicking on the “this is” link below.

The two main competing strategies are:

"always defect" (orange) and "co-operate then always defect" (green).

This is the original example provided by the Philosophy Dept. at Stony Brook, NY.

There are some (old) abstracts of more papers on tit-for-tat and related issues here for anyone interested.