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Q. & A.


WHAT IF LIFE DID NOT ORIGINATE ON EARTH?

By Isaac Chotiner

July 8, 2019
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The Curiosity rover recently discovered methane on Mars, which could be a sign
of life. The biologist and genetics professor Gary Ruvkun wants to search for
DNA on Mars.Source Photograph Courtesy NASA / JPL / University of Arizona

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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?


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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.

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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.





Isaac Chotiner is a staff writer at The New Yorker, where he is the principal
contributor to Q. & A., a series of interviews with public figures in politics,
media, books, business, technology, and more.

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