The Drake Equation is a series of variables used to calculate the likelihood of other intelligent life in our galaxy, the Milky Way. For decades, astronomers have used the equation to estimate the odds that Earthlings are alone in this corner of the universe.
According the equation, it’s reasonably likely that there’s other intelligent life out there. But new research offers some revisions to Drake’s ideas that could drastically reduce the probability of us sharing the Milky Way with other complex life forms.
Robert Stern, a professor of geoscience at the University of Texas at Dallas and one of the paper’s authors, spoke to the Texas Standard about how a planet’s geology can determine its biology.
This transcript has been edited lightly for clarity:
Texas Standard: You have concluded that for a planet to house intelligent life, that planet needs three major geologic features: continents, oceans and long-term plate tectonics. Why are those important for complex life?
Robert Stern: Well, let’s be clear: It’s not complex life. So, for example, whales are very complex. They might be more intelligent than we are, but they couldn’t possibly build a radio that could transmit, and they couldn’t possibly build a rocket ship. So actually we call it advanced communicative civilizations.
So, you know, we needed to evolve from a very simple single-celled organism 4 billion years ago to something that was complex and could swim and had eyes and limbs that could be adapted to crawl out of the ocean onto land, which we did about 400 million years ago. But then, something happened and we started walking and we started looking up, and we started making tools with our hands.
Now, you know, whales and dolphins can’t really study the sky the way a human can. And they can’t possibly make tools – they don’t have fingers; they have flippers.
And the other thing is electricity. I mean, we can’t imagine a life without electricity nowadays. Controlling electricity is completely impossible in the ocean. So for that reason, you’ve got to have an ocean for the nursery and actually all through, you know, quite a bit of the evolution, but you have to have a big place for things to crawl out on land and evolve further and look at the sky and build the things that we built in the last few hundred years.
And what about plate tectonics? How do they fit in?
Now, plate tectonics is is critical. We take that for granted, too, because we have plate tectonics. So the Earth’s outer part is divided into a series of plates that move independently towards each other, away from each other, right by each other. And that creates a flux of lots of things.
Number one, it creates an increased mountain ranges because you get these collisions and those mountains begin to weather and they turn into soils and they wash nutrients into the sea, and these nutrients stimulate life.
And the other thing that happens is that plate tectonics creates new habitats all the time. So these new habitats that plate tectonics creates allows for the isolation and what we call speciation of new genuses. And that’s plate tectonics, you know, the opening and the closing of the oceans, the building of mountain ranges, the breaking up of continents.
These things are much better at creating these isolated habitats than what the other tectonic regime that we see on Venus and Mars have, which is nothing’s really moving around. There’s no major movement of blocks … I mean, continents and oceans don’t mean anything if you don’t have an ocean, right?
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Do we know how many planets in the Milky Way fit this profile?
No. We don’t know how many planets there are in the Milky Way. So, we just started discovering planets – you know, what we call exoplanets – in the 1990s.
And it’s very, very difficult work. Planets are trivial in size compared to the stars they orbit. There’s so many things that have to go right for you to be able to see these planets, that almost certainly there’s many, many more.
I wonder, is this hypothesis limited by human beings’ powers of perception? Could there be life in the galaxy that exists in ways that we are just not able to detect with our senses and technologies?
Exactly. You’ve put your finger on probably the main criticism of our study, and it could be that, okay, science is always failing the imagination test. And I think that’s because scientists are human.
So, yes, if there is some other way of evolving an advanced civilization, it would be fun to learn about it. But just working from scientific principles and thinking about what plate tectonics does and what the absence of plate tectonics does, and thinking about the importance of oceans and continents, we came up with some some reasonable estimates given our sad state of affairs of what’s actually out there orbiting other stars.
I think the dominant narrative is, oh, there’s thousands and thousands of advanced civilizations out there, but they’ve all heard about us, and they don’t want to have anything to do with us.
I know as a scientist, it’s your job to remain dispassionate. But if you could take that hat off for a moment, just as a curious human being, are you at all disappointed by the results of this work?
Oh, not at all. I mean, number one, I’ve been in science writing papers for 42 years. I’ve never seen anything like the interest in this story. I’m grateful, and so is my coauthor, for this remarkable outpouring.
Because we’ve been developing a new approach – we call it bio-geodynamics, and the idea is that organismal evolution is a response that is more controlled by the way the solid planet behaves than most people think. So, for example, Drake, he assumed that, okay, once you get life, any kind of life, it will evolve to intelligent communicative civilization. And so we’ve focused on just that one variable, that fraction of life that evolves to intelligent life.
But I think my coauthor put it best. And the way he put it was sort of humorous: He said the universe would be sorry if our civilization doesn’t succeed.
And I thought that was hilarious. It’s like everyone else is going, we’re doomed – climate change, politics, the standard litany of woes. But it’s like, wait a minute. We’re pretty damn special, and we’re special for a reason.
