The introduction of a new cultural trait may take generations in a society before it takes hold. The variables include the necessity of the trait, the size and degree of interaction of the population, geophysical barriers, and susceptibility.
As an experiment, three months ago I made the first wave of greeting on a one-mile diameter island in the Amazon River. There are four little pueblos of about 200 inhabitants each living on stilted huts that I passed by or under during my daily hikes. Apparently, it was the first time any had seen a hand wave, for all of every age to the last person stared back with puzzled looks. They included farmers, a few dirt floor businessmen, schoolchildren, and entire families at the rate of about fifty people a day.
For the first month of daily hikes, there was zero response and I was like a cloud passing by. Then I began assisting the wave with a hearty ‘Buenos dais´, and the recipients all replied, ‘Buenos dais´, without a wave. However, in about another month the first wave returned from some children who appeared like puppies discovering their tails for the first time, and not knowing what to make of them while they wiggled.
The waves propagated exponentially by imitation of seeing others until three months into the experiment nearly every person I waved to – without the verbal greeting – waved back. Now the island is flooded with them. Do they wave to each other? – I haven´t seen it. However, today 25 out of the 30 people I waved at responded in same, and about a third of them initiated the gesture.
The conclusion is a cultural trait has been instilled in three months. I imagine it will be passed to future generations and last for as long as the happy people do.