For almost seven years, NASA’s Curiosity rover has been exploring the terrain of Mars. Two weeks ago, it made a stunning discovery: relatively large concentrations of methane gas. The rover also found methane in 2013, but the readings recorded this month—approximately twenty-one parts per billion—were about three times as concentrated. The reason this news registered among scientists is that methane is often a sign of life; although the gas can be produced by various chemical reactions, most of it comes from animate beings. Does this mean that we are on the verge of discovering life on Mars, and, if so, what kind of life is it likely to be?

To discuss these questions, I spoke by phone with Gary Ruvkun, a molecular biologist and professor of genetics at Harvard Medical School. Ruvkun has what he admits are somewhat unusual opinions about life’s origins, and about the possibility of finding life elsewhere. In short, he questions the common assumption that our form of DNA-based life began on Earth. What began as an interview about the methane discovery turned into a discussion about why he wants to send something called a DNA sequencer to Mars. (After our conversation, NASA announced that the methane concentrations had descended back to their usual levels, further confounding scientists.) During our conversation, which has been edited for length and clarity, we also discussed the ways in which scientific debates about the origins of life intersect with religious ones, the reasons he might be dead wrong, and what it feels like to hold a minority opinion in the scientific community.

What is your biggest takeaway from this methane discovery?

Looking for methane is a good method to indirectly look for life. The problem is, there are chemical ways to make methane as well. It is not a perfect surrogate for life. So the way most life-detection experiments are proposed from NASA, especially in this era of exoplanets, where so many planets have been detected around stars, is to do spectroscopic studies of their atmosphere. It is always involving abundant chemicals, like methane and CO₂.

Do you think that’s the best way to do it? Or are you suggesting that there’s a better way to do them?

It’s the only way to do it with things that are far away. My favorite way to look for life is to go to a planet and look for DNA. And that assumes that life on another planet would be exactly like life here, which is not how most astrobiologists think about things.

How do you think differently about it?

I think viewing life as having started here is a little bit presumptuous. It seems we’re very, very, very special and it all happened here. I find the idea aesthetically appealing that life as we know it is universal across the Milky Way. It just seems like, once it evolves, it spreads. And one way to argue this is running the clock forward instead of running it in reverse. If we’re really talking about colonizing Mars, step one is to send bacteria to Mars to generate an atmosphere. So if you run the clock forward a million years, presumably, we will be sending bacteria to planets a million light years from us.

O.K., wait, I just want to understand this. So what you’re saying is that you find romantic or nice the idea that other life forms would be like us?

Yeah. That life didn’t start here. It just landed here. That it came from somewhere else. And a lot of people complain about that. They say, "Well, then you’re just putting the problem of origin of life somewhere else." Which is true.

In an e-mail to me, you referred to your views as "not very standard for microbiology." And this is partly because you want to send a DNA sequencer to Mars, yes?

Here on Earth, if you go to some lake or a forest and want to know who lives there, the current method of choice for figuring out who’s there is to just take dirt, make DNA, and do all the genome sequences inside that DNA. And you get a pretty good fingerprint of who lives there. And of course there’s a lot of different kinds of bacteria that live in soils and things like that.

And, if you look in the literature, there are tens of thousands of papers now that do that, and it was done the first time maybe twenty years ago, using DNA as a kind of signature to look for living things. So we would say, "We’ll just do that on Mars and do the sequence." And you could ask, "Well, do you find anything there that looks like it’s our cousin?" It doesn’t have to be our brother. It can just be more distantly related than a brother, but a cousin, and therefore coming from the same tree of life. Once you do that, you can say, "Oh, well, life on Earth and Mars is similar, and that’s sort of the least-interesting idea, because Earth and Mars are right next to each other." So it’s kind of almost obvious that they would share the same kind of life, because there’s an exchange. But what if it actually is the entire Milky Way that has the same life?

What would people who are skeptical of the way you’re thinking about it say in response to this?

They’d say that’s just stupid. [Laughs.] Because they’re saying, "Well, it had to start somewhere, and so why would you not think it started here? Why are you positing that we caught life instead of evolved it?" Because there’s clearly evidence for how life evolved in our genomes. It’s what’s called the RNA World, which was kind of the earliest form of life, and is still present in our genomes. We can see it there, and so you can discern early steps in evolution just by looking in modern genomes. In orthodoxy and all the textbooks, the RNA World—that’s kind of the precursor to the DNA world—was here on Earth four billion years ago. And I would propose, no, it was probably ten billion years ago, somewhere on the other side of the Milky Way, and it’s been spreading all across the Milky Way.

So the four-billion-year and the ten-billion-year estimates—there is no scientific basis for either estimate? Is that what you are saying?

No, no, no. The Earth is 4.5 billion years old. And the universe, at least based on estimates from the Big Bang, is something like fourteen billion years. So, if life evolved somewhere else, that buys you about ten billion years of time. But I’d rather it bought you a hundred billion years of time or a thousand billion years of time. That would be more satisfying.

Why would it be more satisfying?

Well, because it allows more time. See, the thing is, if you look in the fossil record, where’s the first evidence of life? Well, you can see evidence of bacterial life, things that look like bacteria, the things that are called stromatolites, which are a kind of blue-green algae bacteria that live in colonies. Those things form good fossils, and you can see those about three and a half billion years ago. So, life had already evolved to the point of there being pretty complicated bacteria very quickly, after the Earth cooled.

And, you know, most lay people would say, "Well, yeah, duh, bacteria are pretty simple." But bacteria are not simple. Bacteria are incredibly complicated. Bacteria are the self-replicating robots that electrical engineers dream of. These guys can make a copy of themselves in twenty minutes, with four thousand parts.

So, O.K., what’s the upshot of what you’re saying about the bacteria?

They were super highly evolved, and I think they got here as soon as the Earth cooled, and they just started growing. And they’ve been spreading across the Milky Way and maybe the whole universe. For example, you’ve heard about SETI, right? The people who are looking for intelligent life?

Yes. [I hadn’t, really.]

Usually, they’re mathematicians, and they expect the smarty-pants on some other galaxy to be sending pi or, you know, some mathematical signal. And, really, what they’re all going to be sending is DNA sequences.

So you’re saying that life came here as it spread to other places, too. And, so, if we send the DNA sequencer out and we find that it suggests that this stuff was spreading and then came to Earth, not that we are the origins of everything—

Exactly.

So the other people, the people who think differently about this than you, think, No, our version of life started here, and there may be other types of life on other planets, which we would still get from methane or something like that? And so we should look for things like methane, because we might just see totally different types of life.

Exactly, yes. This field of astrobiology is a field of people who think about life on other planets. And there’s probably, I don’t know, a thousand to five thousand people who would call themselves astrobiologists, and NASA has done a very good job of fomenting that field. And, if you asked a thousand astrobiologists, do they believe life spread or it’s independently evolved, I would say one per cent would buy into the idea of life spreading the way I’m sort of promoting it.

O.K., so if ninety-nine per cent of scientists believe in global warming, and a tiny minority say that it’s not man-made or not happening, whatever, we roll our eyes and we say, "Well, that’s not really scientific." These people are fossil-fuel-industry hacks or something along those lines. You’re obviously an extremely respected scientist, who is not looked at as a kook. Does this give you some degree of pause or self-reflection?

If I was rational, you’d probably be right. [Laughs.] But I don’t know why. It’s just caught on. Basically every textbook talks about the origin of life being on Earth and it is a little ad hoc to say, you know, oh, we just flew in here. You know? It’s sort of not satisfying in a way because it puts the problem off somewhere else. Right? It’s still had to of start somewhere else.

I think what I’m gagging on is this idea that it’s so easy to go from a bag of chemicals to full bacteria, and that it would have happened in a couple of hundred million years on Earth. The other thing that you have to realize is that, with plate tectonics on Earth, Earth erases its history very, very quickly, because the continents are drifting around and the crust is getting recycled. It’s very hard to find samples that are more than three billion years old. There’s not a lot of them on Earth. So looking for the oldest fossils is kind of hard here. And that’s actually one of the advantages of looking on Mars—they don’t have plate tectonics. So, if you want to find old things on Mars, it hasn’t continually been sort of burying its past like we have here.

What discovery could be made on Mars that would suggest to you that you were right or you were wrong in your theory about this?

Well, I mean, again, if you did DNA sequencing there, which is super sensitive, right? So you can find extremely rare organisms on Mars. And if you found it, and if you found that it wasn’t just, you know, dandruff or acne that came from the spacecraft-assembly room but it was deeply branching—that is, it’s related to life on Earth, but sort of in the same way that a kangaroo is an animal but it’s clearly different than anything else you saw in the old world—then you know that you found something new, right? And it’s that way with bacteria, too.

Or if the SETI people ever got a signal that had four symbols, like a DNA sequence, and if you did a substitution code and said, "Oh, my God, this looks like some of the genes we recognize"—this is the evidence that there’s a commerce in genomics out there on some other planet.

And what discovery could convince you that you are wrong or that you’re in the minority for a reason?

So, if somebody found an entirely new life form that’s not DNA-based, I think that’s pretty good evidence against this idea of Panspermia.

I’ll let you go in a minute, but what if it started here and then spread elsewhere? And so we found some sort of DNA on Mars, but that’s because it spread there from Earth. Is that possible?

Yeah, but that sort of places us at the center of the universe, and all the force of history is to say, "Don’t think of us as the center. We’re nothing."

What are the religious implications here? Do you find any sort of religious aspect to this debate?

So I sent you a link, or I told you to search for the video? [Ruvkun had suggested that I watch a YouTube video of his views on "life away from earth."]

I watched the video.

So one of the things I did in that video that I was a little bit wary that I did is I refer to the wonderful motor the ATP synthase. This is one of the most amazing little machines that bacteria have, for generating energy by pumping protons across membranes. And they basically have a molecular motor that rotates it, I don’t know, a thousand r.p.m. or something.

So the intelligent-design people—I’m almost wary to tell you this, because the last thing I want is for what I’ve said in public to be interpreted by intelligent-design people—they use ATP synthase as their poster child for intelligent design.

ATP synthase is what?

It’s the little rotary motor that generates ATP by using proton pumps. It’s absolutely a beautiful piece of evolution. And I want to stress that I believe it’s evolution, but it’s also used by religious fanatics to say how evolution couldn’t have done this, because it’s so beautifully designed.

And so what does that have to do with the two theories—

Well, there are religious fanatics who use the same example that I use. I use that example to say, "This is so highly evolved." You know, you’re not talking about primitive life three and a half billion years ago. You’re talking about very highly evolved life. It had already reached a high plane of evolution.

I see. And they say that shows that humans are so special because God created us?

Yes. And I say, "No, it’s because there’s been a lot more time than four billion years."

I assumed you were going to say the opposite about the religious dimension, that your theory doesn’t look at Earth as the center of things, and so religious people don’t buy it. Whereas the other scientists’ belief would at least be more akin to some kind of religious belief, because it sees Earth as the beginning.

Yeah. I don’t think—well, it could be that the orthodoxy of origin of life on Earth has its roots in Adam and Eve. I don’t know. It could be that I’ve never had a religious thought in my life.

Shocker. How easy is it to send one of these sequencers to Mars? And will it happen anytime soon?

Well, NASA has been supporting us. Maria Zuber—who’s a card-carrying planetary scientist, she’s a real space person—and I have been working on this together for almost twenty years, and NASA has supported it. It’s a high-risk endeavor that they’re willing to throw some dough at, but they have not approved it for flight yet.

They’re not yet there. On the other hand, if you look at how NASA runs itself, it’s quite interesting. Every ten years, they do what’s called a decadal survey, where they go around and talk to all the planetary scientists in the U.S. and Europe and the world and ask them, "What do you think is the most important thing to do?" And they distill this down to a two-hundred-page document, and, if you look at their priorities for what they think is important as a space organization, looking for life on other planets is their No. 1 priority.

Do the increased methane levels say anything about this debate?

Most astrobiologists would say, "Oh, well, maybe there’s methanogens." Those are bacteria that take in carbon dioxide, use hydrogen from the soil, and generate methane. That’s a metabolism. And most astrobiologists would say, "Oh, the methane could come from microbes." And so, yes, I think probably many people would like the idea of methanogens on Mars.

And probably a lot of them would say, "Yeah, the idea that they might be related to methanogens on Earth is not crazy."

So, just to clarify, my takeaways from this conversation are that you believe in intelligent design, you don’t believe in global warming, and you have crazy views about life on other planets.

Wait, wait. [Laughs.] Oh, no, don’t. This will be the end of my career.

An earlier version of this piece misstated the type of device Ruvkun wants to send to Mars and the enzyme that makes ATP.