Overbye points out that only about 3% of the human genome encodes genes, and the remaining 97% which he calls "junk DNA" could be used to store information. Of course the stretches of DNA that don't encode proteins aren't simply junk; they contain sequences that control the when and in which cells the genes are expressed, for example. Just because some sequences don't have a known function does not mean that they necessarily have no function*. Even with functional non-coding DNA, however, there are likely spots where messages could be inserted. Of course it's not quite as simple as simply inserting the code: over many generations mutations would likely completely corrupt the message sequence.
If there was a message inserted into our DNA would we even be able to recognize it? If it were placed there millions of years ago, it certainly won't be in English, and Bejerano points out that people who are looking for codes will probably see messages, even if they aren't there**. It would have to be in some kind of universal language. University of Arizona cosmologist Paul Davies suggests a way it could work:
Calling the idea of storing information in living DNA “a nifty idea,” [UC Santa Cruz geneticist Gill] Bejerano said: “The bottom line is if you want something to perpetuate forever, you can’t just come in and type what you want. It would get washed away.”
That dream, he said, “is hopeless with our current knowledge.”
If we want to leave a message that would last for eons, it seems, we have to be clever enough to make sure that the message would remain beneficial to its host pretty much forever.
Davies figures the notion is "probably no dafter than radio SETI," which is more a comment on that project than the likelihood of messages in our DNA.
A good way to do this would be to use the letters to represent pixels on a screen tracing out a shape like a circle - an idea mooted in a different context by the late Carl Sagan in his novel Contact. That way, the artificial nature of the pattern would still be apparent even if a few pixels got scrambled.
The arresting pattern would serve to flag the message itself, which would otherwise be overlooked as a meaningless jumble. The message would then need to be decoded with the help of a computer. What would ET have to say to us? Most likely, any message in the genome would be rather basic, like people waving between mountain tops.
It might contain the co-ordinates and transmission times of a conventional radio message, broadcast every century, perhaps. Or it could direct us to a larger artefact located safely in the fringes of our solar system, in which we would find the entire contents of an encyclopedia galactica, including the rise and fall of ET's civilisation, which may have died out long before human beings even existed.
Science fiction writers seem to like the idea too. James Hrynyshyn of The Island of Doubt points to the Star Trek: TNG episode "The Chase." Some other examples of fiction featuring ancient "more than junk" DNA are David Zindell's Neverness and Robert J. Sawyer's Frameshift. I'm sure there are a number of others.
*The 2003 Scientific American article "The Unseen Genome: Gems among the Junk" for a layman's explanation and examples.
** There are codes in the amino acid sequences of proteins, though. That's where ELVIS still lives!
Tags:science fiction, junk DNA