DNA is one of those things that becomes more amazing the more you think about it.
Inside almost every cell in your body is a copy of your DNA. The human genome contains roughly three billion base pairs, all built from combinations of only four chemical bases.
A. C. G. T.
That’s it.
Four letters, repeated in different combinations, contain the genetic information needed to build a human being.
Obviously, it’s much more complicated than that. DNA isn’t a computer program, even though we often talk about it that way. Nobody sat down and wrote it. What we have today is the result of billions of years of evolution, mutation, natural selection, duplication, deletion, and probably a lot of biological accidents along the way.
But DNA does store information.
That got me thinking about something.
If you wanted to hide information somewhere and wanted it to survive for an incredibly long time, could you put it inside DNA?
And if someone had already done that, would we even know what we were looking at?
When scientists began sequencing the human genome, one of the surprises was how little of it directly codes for proteins.
Humans have around 20,000 protein-coding genes, but the protein-coding portions make up only a small percentage of our DNA.
So what’s everything else doing?
For years, a lot of non-coding DNA was casually called “junk DNA.” That gave people the impression that most of our genome was useless material left behind by evolution.
That’s not really an accurate way to look at it.
Some non-coding DNA helps control when genes turn on and off. Some is involved in chromosome structure. Some produces RNA that has a function of its own. There are repeated sequences, old copies of genes, genetic material that has moved around, and plenty of other things.
And there are still parts we’re trying to understand.
That doesn’t mean something mysterious is hiding there. Not knowing what something does isn’t evidence that aliens put it there.
It just means we don’t know yet.
But some of what we’ve already discovered is strange enough without needing aliens.
This is one of my favorite things about genetics.
Viruses have been infecting living things for a very long time.
Retroviruses can insert their genetic material into the DNA of the cells they infect. Usually that doesn’t become part of the species permanently. But if viral DNA ends up in a reproductive cell and gets passed to offspring, something unusual can happen.
The viral DNA becomes inherited.
Then the next generation carries it.
And the next.
Millions of years later, descendants can still carry pieces of that ancient virus.
Humans do.
Over time, mutations usually damage the viral sequences so they no longer behave like the original virus. What remains is basically a genetic fossil.
Think about that.
You’re carrying evidence inside your body of infections that happened to your ancestors millions of years before you were born.
DNA isn’t just instructions.
It’s history.
And once I started thinking about DNA that way, I started wondering what else could survive in it.
We like to compare DNA to computer code, but I don’t think that’s quite right.
Computer code is written for a purpose.
Biology isn’t.
Evolution works with whatever is already there.
Something gets duplicated. One copy changes. A virus inserts something. Another section gets damaged. A mutation happens. If the organism survives and reproduces, that change might get passed along.
Then evolution keeps building on top of it.
Nobody cleans up the old code.
Nobody starts over.
Nobody says, “This is getting messy. Let’s rewrite the whole thing.”
So our genome isn’t a perfectly organized instruction manual.
It’s more like a document that’s been copied and edited for billions of years by people who never saw the original.
Some paragraphs have been copied twice.
Some have been deleted.
Some were added from somewhere else.
Some no longer make much sense.
And somehow the whole thing still works.
Here’s where you have to be careful.
Finding a mathematical pattern in DNA wouldn’t automatically mean anything unusual.
Nature creates patterns everywhere.
Look at the spiral arrangement of seeds in a sunflower. Look at the branching of trees, blood vessels, rivers, and lungs.
Mathematics describes the natural world because the natural world follows physical rules.
DNA is no different.
There are repeated sequences, statistical patterns, structural relationships, and all kinds of things that can be described mathematically.
There’s another problem.
The human genome has about three billion base pairs.
Search through three billion pieces of anything and you’re eventually going to find coincidences.
So let’s say someone finds a DNA sequence that can be converted into:
2, 3, 5, 7, 11.
Prime numbers.
Interesting?
Yes.
Proof of intelligent design?
Not even close.
But what if it didn’t stop?
This is where we leave established science and start playing with an idea.
Suppose researchers found a section of DNA containing a mathematical pattern.
They assume it’s a coincidence.
Then the pattern continues.
2, 3, 5, 7, 11, 13, 17, 19, 23…
Not five primes.
Not twenty.
Hundreds.
Then they find something else.
Geometry.
Mathematical constants.
Repeated structures.
Maybe one section seems to explain how another section should be read.
Then someone notices that damaged pieces of the sequence can be reconstructed using information elsewhere in it.
Basically, error correction.
Now you’ve got something interesting.
That still wouldn’t mean scientists would announce that aliens had modified our DNA.
They’d do the opposite.
They’d assume something was wrong.
Sequencing error.
Contamination.
Software problem.
Unknown biological process.
Statistical coincidence.
They’d try to tear the discovery apart.
And that’s exactly what they should do.
But what happens when they can’t?
That’s the point where things get interesting.
Prime numbers show up in science fiction all the time when we’re talking about communication with extraterrestrial intelligence.
There’s a reason for that.
Prime numbers aren’t a human invention.
Our symbols are.
We decided that this symbol—”11″—represents eleven.
Another civilization might represent eleven completely differently. They might not even count in base ten.
But eleven is still prime.
You can’t divide eleven objects into equal groups other than one group of eleven or eleven groups of one.
That mathematical relationship exists whether humans are around to notice it or not.
So if we received a signal from another star containing a long sequence of prime numbers, people would pay attention.
Not because nature can’t produce strange patterns.
It can.
But because a long, deliberate mathematical progression would be difficult to explain as an accident.
Now imagine finding that same kind of progression inside DNA.
The obvious question would be:
How did it get there?
Then you’d have an even bigger problem.
How long has it been there?
This is one of the problems I had to think about when playing with this idea.
DNA isn’t permanent.
It mutates.
Species go extinct.
Entire branches of life disappear.
If you put a message inside one animal today and came back 100 million years later, there’s a pretty good chance that animal and every descendant carrying your message would be gone.
So how would you make a message survive?
Maybe you put copies everywhere.
Maybe you put it in DNA important enough that evolution tends to preserve it.
If a mutation destroys something an organism needs to survive, that organism is less likely to reproduce. Natural selection ends up protecting the important sequence.
But there’s another possibility that I find much more interesting.
Don’t put the message in one species.
Put it in life.
Imagine someone visited Earth a very long time ago.
Not thousands of years ago.
Not even millions.
A billion years ago.
They find primitive life and change something inside it.
Then they leave.
Life keeps going.
Species evolve.
Species disappear.
Continents move.
Oceans form and vanish.
Asteroids hit.
Ice ages come and go.
Eventually animals appear.
Then dinosaurs.
Then mammals.
Then us.
The original organism carrying the sequence has been gone for an unimaginable amount of time.
But descendants of that organism are everywhere.
Eventually humans learn how DNA works.
We sequence ourselves.
Then we sequence other primates.
Mammals.
Fish.
Plants.
Fungi.
Bacteria.
Nobody notices anything at first because no single species has the entire sequence anymore.
Humans have one piece.
A fish has another.
A plant preserved something we lost.
Some microorganism contains another section.
Then somebody puts them together.
Suddenly the pieces form something that couldn’t possibly be accidental.
That’s the kind of discovery I would love to see unfold.
Not because I think it’s actually hiding in our DNA.
Because of what would happen if it were.
This would be incredibly difficult.
Saying something “looks designed” isn’t enough.
Nature produces things that look designed all the time.
Scientists would need something much stronger.
Imagine reconstructing a sequence and discovering that the first section establishes a number system.
The next contains prime numbers.
Then geometry.
Then a mathematical constant.
Then instructions for decoding another section.
Each piece builds on the one before it.
At some point, the odds of all of that happening naturally would become very hard to defend.
Scientists would argue about it.
A lot.
Some would insist there had to be a natural explanation we hadn’t discovered yet.
Others would start considering the possibility that nobody would have taken seriously a year earlier.
Someone made it.
And if that were eventually proven, finding out who made it might not even be the most important question.
The first thing I’d want to know is:
When?
Imagine finding an artificial sequence shared by humans and chimpanzees.
That means it predates the point when our evolutionary lines separated.
Find it in other mammals and it gets older.
Find related pieces in reptiles, fish, plants, fungi, or microorganisms and suddenly you’re going very deep into Earth’s history.
Eventually you’re no longer asking whether somebody modified humans.
You’re asking whether somebody modified life on Earth.
That’s an entirely different question.
It would mean someone was here before humanity.
Maybe before mammals.
Maybe before dinosaurs.
Possibly before complex animal life existed at all.
At that point, human history becomes a very small part of the story.
This is where the idea gets a little darker.
We would naturally assume that anything hidden inside our DNA was meant for us.
Why?
Humans tag animals all the time.
Scientists put bands on birds. We tag sharks and whales. We implant tracking devices in animals.
The tag isn’t meant for the animal.
It’s meant for us.
So what if an artificial sequence inside Earth’s DNA wasn’t a message to humanity?
What if it was a label?
Maybe it identifies this planet’s biosphere.
Maybe it’s a date.
Coordinates.
A warning.
A catalog number.
Maybe whoever put it there never expected the life carrying it to become intelligent enough to read it.
That’s a much more interesting possibility to me.
Because now we’re not reading a message.
We’re reading the label someone put on us.
This is where the science-fiction part runs into something we’re already doing.
Researchers have stored digital information in synthetic DNA.
Text, images, and other digital files can be converted into sequences using the same basic chemical alphabet biology uses. The DNA can then be synthesized, stored, sequenced, and converted back into digital information.
There are good reasons people are interested in doing this.
DNA can store an enormous amount of information in a very small space.
That doesn’t mean we’re capable of safely putting a complex message into living organisms and expecting it to remain readable for a billion years.
We’re not.
But the basic idea of using DNA to store information isn’t science fiction anymore.
We’ve already done it.
So the leap isn’t:
Can DNA contain information someone intentionally put there?
We know it can.
The leap is:
What if somebody figured that out long before we did?
This was one of the ideas that eventually worked its way into The Inheritance War.
I kept coming back to the same thought.
If humanity ever discovers proof that someone else has been to Earth, why does it have to be a crashed spaceship?
Why does it have to be a pyramid?
Why does it have to be something buried underground?
What if the evidence has been sitting right in front of us?
Better yet, what if it’s been sitting inside us?
I started imagining the scientist who finds it.
She doesn’t immediately think she’s discovered aliens.
She thinks she made a mistake.
So she runs the test again.
Same result.
She checks the equipment.
Nothing wrong.
She checks the software.
Runs another sample.
Then another.
Eventually she reaches the point every scientist probably both dreams about and dreads.
The data is right.
What she’s looking at shouldn’t exist.
But it does.
That’s a much more interesting beginning to me than a spaceship suddenly appearing over a city.
Although, eventually, spaceships can create their own problems.
There is no credible scientific evidence that extraterrestrials placed a message inside human DNA.
I want to be clear about that.
The real story of DNA is already incredible.
We carry the results of billions of years of evolution. We carry mutations inherited from people who lived long before us. We even carry genetic remains from viruses that infected our ancestors millions of years ago.
We’re still learning how parts of the genome work.
None of that requires aliens.
But science fiction gives us the freedom to take something real and move it one step farther.
DNA stores biological information.
That’s real.
Humans can deliberately store non-biological information in DNA.
That’s real too.
An extraterrestrial civilization placed a mathematical signature inside life on Earth a billion years ago?
That’s where I start making things up.
But the question behind it is still interesting.
If you wanted to leave information somewhere that might survive long enough for an intelligent species to eventually find it, where would you put it?
A building will eventually collapse.
Metal corrodes.
Mountains erode.
Continents move.
Even civilizations disappear.
Life does something different.
It makes copies.
Then those copies make copies.
Again.
And again.
For billions of years.
Maybe the greatest archive on Earth wouldn’t need to be buried somewhere waiting for us to find it.
Maybe it could have been traveling with us the entire time.
And if we ever did find an unmistakably artificial signature buried inside the DNA of life on Earth, we wouldn’t have to ask whether we’re alone anymore.
We’d already have the answer.
I’d want to know something else.
How long have they known about us?
D. M. Bachmann is the author of The Inheritance War, a science-fiction novel exploring DNA, deep time, first contact, and the possibility that humanity doesn’t know the whole story of life on Earth.
