Tuesday, July 03, 2007

Messages in Our DNA?

Dennis Overbye has an essay in the June 26 issue of the New York Times that discusses the possibility that DNA could be used to store messages - and perhaps that there already are messages from ancient aliens in our genomes. His starting point is the recent work of Masaru Tomita and colleagues at Keio University, who encoded Einstein's famous formula, E=mc2, and the year of its derivation, 1905, into a bacterial genome.

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.

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.

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:

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.

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.

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!



A.R.Yngve said...

Alien messages in DNA... that reminds me of a (rather morbid) 1-page comic-strip I made years ago.

The strip "explained," step-by-step, why we've never seen alien visitors: Some alien civilization has seeded other worlds with a genetic virus which actively prevents other intelligent beings from ever going into space.

The virus rides "piggyback" in mitochondrial DNA over countless generations, until it is exposed to cosmic radiation... such as happens to astronauts... which triggers the virus reproduce itself, until the host astronaut bursts... leaving behind a fresh new batch of viruses to spread through space and infect other lifeforms (and astronauts)!

A very nasty idea, and of course it couldn't happen... right?

Peggy said...

A.R.: That is a wonderfully nasty idea! I don't think that latent viruses hidden in mitochondrial DNA are any less likely than alien messages in our genomic DNA ;-)

I more uplifting take on "ready to be activated" alien sequences is in Spider and Jeanne Robinson's Starmind.
SPOILER! - - - In the final novel of the Star Dance trilogy it turns out that junk DNA is actually there to help us take our place among the stars.- - -/SPOILER!

Talia Mana said...

I have to admit I raised my eyebrows at the alien messages in DNA. I can see it making for a great theme in scifi books

Dídac López said...

Well, I suppose that looking for patterns in non-coding DNA may be useful to understand all-genome function and structure.

The idea of searching a "designer-made" message of DNA reminds me the proposal made by Carl Sang in Contact about a message encoded in mathematical constants such as PI. We don't know for sure if PI is a normal number or not. I suppose it would be easier to process DNA information from the several genome projects.

The question put by a.r.yngve is really interesting from an epistemological point of view. If an alien designer of life on Earth want to be "invisible" from its creatures, then the so-called undetectability conjecture may play a role.

However, I'm not convinced in the explanatory power of the "alien-designer hypothesis" to understand life on Earth. So, paraphrasing Laplace, I think we don't need aliens playing with our genomes to understand them.

Evan Soe said...

I imagien that if there were a hidden message in our genome it would say something along these lines: "There is no inherent meaning in anything. Stop looking for one, you fool."