I have long been interested in how memories of significant events live and die among populations. This is important, because these memories are not neutral, and carry values, fears, hopes and expectations that are often transmitted to future generations.
I suspect few events are more significant, and traumatic, for survivors than major natural disasters. Perhaps the most significant in Southeast Asia in living memory was the December 26 2004 tsunami, but there are already adults with no memory of that event.
As result, what I term “peak memory”, the time when the biggest percentage of adults with a distinct memory of that disaster, has already passed. Taking as a starting point the age of memory for a child as being five years old, that would mean for 13 years after the event new adults would have a memory of the event, but from that time (in this case the year 2017) the total percentage with memory will diminish more adults emerge with no memory of the event and those with a memory of the event pass on.
Nevertheless it will be a long time into the future before nobody has direct experience of the event. Noting again the selection of the age of first memory at five years old, and assuming nobody who experienced that event lives beyond 100 years of age, direct memory of the December 26 2004 tsunami will collectively die in around 2099.
This timeframe may also be understood by looking at historical examples.
My grandfather, who died in 1992, was born in 1907. As a result, he undoubtedly met someone who remembered, and possibly heard, the Krakatoa explosion (see here) just 24 years before his birth. What is far less likely is that he met someone who remembered the Tambora eruption (see here) some 92 years before he was born.
That would suggest peak memory of Tambora lasted from 1815 to around 1828, and direct memory ended in about 1900, several years before his birth. If, however, a 5 year old encountered one of the last of those with direct memory of Tambora then that (then) 5 year old could have carried that shared memory through to around 1995.
In contrast, the Krakatoa eruption, which now seems an impossibly distant 135 years ago, would have existed as a peak memory until 1898, a direct memory until 1978 and will possibly endure as a shared experience until 2073.
And the December 26 2004 tsunami? Well, as mentioned above peak memory would have ended less than two weeks ago and direct memory will pass around 2099, but personal knowledge of someone who lived through that time will linger until possibly the year 2194.
Those memories can indeed experience a long life.