The 100th Monkey Effect?

[Jim Lane]

2. The "hundredth monkey" effect is a New Age urban legend

Some monkeys figured out the benefits of washing sweet potatoes and taught others, that's all. In particular, the startling "jumping across the sea" effect, supposed evidence of a collective unconscious, has not actually been observed.

A summary of the debunking:

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 observational learning, which is widespread in the animal kingdom;[8] 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 by the Japanese scientists was on the order of years so the increase in the proportion was not observed to be sudden.

Claims that the practice spread suddenly to other isolated populations of monkeys may be called into question given the fact that at least one washing monkey swam to another population and spent about four years there and also the monkeys had the researchers in common. Amundson also notes that the sweet potato was not available to the monkeys prior to human intervention.[1][8]

(From the "Hundredth monkey effect" article in Wikipedia)