The idea comes from this (which I came across via an article in last week's customers' magazine from the supermarket Waitrose):
Barcoding wild SalmonPerhaps the distinction between natural and semantic information is not so clear after all. [Later thoughts after the comments below: I don't think this scenario affects the distinction. It is just that the tree-rings, or the ear-rings, can be used to convey semantic information.]
To increase wild salmon populations in Alaska, hatcheries raise batches of salmon from eggs and release them into the wild. The little fish are held just long enough to remember the scent of the stream where they will later return to spawn.
How do scientists tell the difference between a salmon born in a wild fish hatchery and one born in a stream? The answer, barcodes.
For almost thirty years, fish were tagged by removing an unnecessary fin and placing a metal id tag in the fish’s nose. However, this process was time consuming, and only about a tenth of the fish that came from hatcheries could be marked.
Researchers then discovered that a kidney bean shaped bone in the salmon’s inner ear, called an “otolith,” is sensitive to water temperatures during embryonic development. When the temperature of the water running over the salmon eggs is raised by a few degrees, the developing otolith adds a darker layer of calcium to its surface. This is done repeatedly to the embryos. Later on when the adult fish return to spawn and are harvested, the otolith can be removed and cut in half to reveal a pattern of dark rings.
By reading this “barcode,” the hatchery can tell which batch the fish came from and how long it had been in the wild.
In a diagram with trapeziums the decoding would be the same, regardless of how the tree/ear rings were created - whether they were due to natural conditions or human coding. The difference would be in the coding. In one case you could draw a trapezium for the encoding, the human control of the growing conditions, in the other, well, you could still draw the trapezium but it would represent the natural conditions.
The point, though, is that in both cases the rings are a medium for communicating information, no different conceptually from, say, a genuine barcode.