I got this from Wikipedia, as it states most clearly what I wanted to say, I'm just copying it here for your examination:
"The story of the hundredth monkey effect was published in the foreword to Lawrence Blair's Rhythms of Vision in 1975. The claim spread with the appearance of Lifetide, a 1979 book by Lyall Watson. In it, Watson repeats Blair's claim. The authors describe similar scenarios. They state that unidentified scientists were conducting a study of macaques monkeys on the Japanese island of Koshima in 1952."
These scientists purportedly observed that some of these monkeys learned to wash sweet potatoes, and gradually this new behavior spread through the younger generation of monkeys—in the usual fashion, through observation and repetition. Watson then claimed that the researchers observed that once a critical number of monkeys was reached—the so-called hundredth monkey—this previously learned behavior instantly spread across the water to monkeys on nearby islands.
Michael also mentions this story at the end of his documentary, only he says it is a coconut, rather than a sweet potato.
The effect discredited
An analysis of the appropriate literature by Ron Amundson, published by the Skeptics Society, revealed several key points that demystified the supposed effect.
Unsubstantiated claims that there was a sudden and remarkable increase in the proportion of washers in the first population were exaggerations of a much slower, more mundane effect. Rather than all monkeys mysteriously learning the skill it was noted that it was predominantly younger monkeys that learned the skill from the older monkeys through the usual means of imitation; older monkeys who did not know how to wash tended not to learn. As the older monkeys died and younger monkeys were born the proportion of washers naturally increased. The time span between observations was in the order of years.
Claims that the practice spread suddenly to other isolated populations of monkeys may be dis-proven given the fact that at least one washing monkey swam to another population and spent about four years there. It is also to be noted that the sweet potato was not available to the monkeys prior to human intervention.
This may be a social myth, but it does exemplify a point. One of critical mass. When some things reach a critical point, it can suddenly explode across the board. Change can suddenly happen. You can put up with something as status quo, then when you least expect it, it can change, bounce 180 degrees. Be aware of it. Notice, when it happens, was it explainable, something building to a point of change? Or, was it unexplainable, and something that was building, then suddenly tips the scale and appears to be far more than it every appeared to be.