Learn about the “superhabitable” planets that may have conditions better for life than Earth. Then, biologist and best-selling author Neil Shubin will explain a common misconception about how animals evolve.
Learn about the “superhabitable” planets that may have conditions better for life than Earth. Then, biologist and best-selling author Neil Shubin will explain a common misconception about how animals evolve.
Two dozen planets have been identified that may have conditions better for life than Earth by Grant Currin
Additional resources from biologist and author Neil Shubin:
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Find episode transcript here: https://curiosity-daily-4e53644e.simplecast.com/episodes/what-people-get-wrong-about-evolution-w-neil-shubin
[MUSIC PLAYING] ASHLEY HAMER: Hi. You're about to get smarter in just a few minutes with Curiosity Daily from curiosity.com. I'm Ashley Hamer.
NATALIA REAGAN: And I'm Natalia Reagan. Today, you'll learn about super habitable planets that may have conditions better for life than Earth. Then biologists and bestselling author, Neil Shubin, will explain a common misconception about how animals evolve.
ASHLEY HAMER: Let's satisfy some curiosity.
[SWOOSH]
NATALIA REAGAN: As far as planets go, Earth seems well, unbeatable. We've got mild temps, liquid water, and atmosphere. What more could we want, aside from teleportation? Well, I'm about to tell you. Because it turns out that Earth may not be the best possible place for life out there.
Scientists have recently identified a couple dozen faraway planets that aren't just habitable. They're super habitable. That means, they might even be friendlier to complex life than Earth. To be clear, there's no evidence that any of these 24 exoplanets are home to any life at all. But they sure have a lot of potential.
The first criterion that all the contenders have to meet is probably obvious, they had to have liquid water. That's most likely to happen when a planet is at the right distance from its star, not too close, not too far. That's a box that Earth can check too.
Next, the researchers considered the star of the planet orbits. The sun is what's called a G star. There's nothing wrong with G stars. But they have a small drawback when it comes to the appearance of life, a short lifespan. The sun will be lucky to see its 10 billionth birthday. That's less than ideal, because life takes forever to emerge.
The sun lucked out. It was about 1 billion years old when Earth got its first life forms. But other G stars might not be so lucky. That's why researchers paid a lot of attention to planets orbiting K dwarf stars. They don't burn as bright or hot as G stars, but they do last a lot longer. We're talking 20 billion to 70 billion years. That means, their planets will be older too.
That's good news. Because researchers think life is most likely to develop on planets that are old, but not too old, probably, 5 billion to 8 billion years old. That's enough time to give life plenty of chances. But not so much time that geothermal energy goes away completely.
Bigger might also be better. A planet 10% more massive than Earth would have even more surface area. And a planet 50% more massive would have enough extra gravity that its atmosphere would stick around for longer. That would give life more time and space to do its thing.
Finally, super habitable planets tend to be more humid and a touch warmer, about 8 degrees Fahrenheit to be exact. That might come as a surprise given that a much smaller increase in our global average temperature is an existential concern. But remember, these super habitable planets are good for a theoretical life in general. A concept astrobiologists have developed to help them analyze exoplanets. Life as we know it evolved on Earth. And that's almost certainly the best place for it to Thrive
[SWOOSH]
ASHLEY HAMER: There's a classic argument people make against the theory of evolution that goes something like this, for something as complex as a wing to evolve, there had to be steps along the way where an organism had half a wing. But what's the use of half a wing? Well, today's guest is going to give you the answer.
Neil Shubin is a biologist and bestselling author. And his latest book is entitled, Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA. He says it's a common misconception that when birds evolved to fly, they evolved wings. But it's just not true. I asked him if he could tell us what's really going on.
[SWOOSH]
NEIL SHUBIN: In fact, it's a general principle. The features we always associate with the great transitions, the great revolutions in the history of life, never happened at those revolutions. They always appeared before.
So if you naively think that when fish evolved to walk on land, they evolved lungs. They evolved arms and legs. You naively think that when birds evolved to fly, they evolve feathers. And in each one of those cases and many more, that's manifestly not true. Lungs were around for eons before fish took their first steps on land. Bones that make arms and legs, and wrists, and so forth were around for millions of years before animals took their first steps on land.
What it turns out, the more we look, the more we find that the revolutions happened, not by the origin as much of new structures, but by repurposing, using old structures and new ways. So lungs originally appeared in fish well before animals took the first steps on land. And those fish had both lungs and gills. And we know this from DNA research. We know this from the fossil record. It's a fact.
And what these fish were doing is they were using lungs to live in water that has variable oxygen content during the year. So they'd use their gills when the oxygen content was high. And then they'd shift to lungs when the oxygen content got really low. Well, that strategy was around long time, as were arms and legs, and the fins of different fish. But at some point in the distant past, then those things were repurposed for life on land. So these major revolutions aren't about always evolving new structures, they're about using old structures that existed for different reasons in new ways.
ASHLEY HAMER: Wow! It's hard to imagine. I mean, the lung one makes total sense. But what about-- A Lot of people will say, part of a wing-- how useful is half of a wing? Like what were wings doing?
NEIL SHUBIN: So let me just take it even further back. What uses half a limb? Remember, I told you that arm bones first appeared in fins. Well, the fish that gave rise to limbed animals walked on-- They were using-- The training wheels for them, where they were walking on water bottoms. They were supporting themselves with their fins in the water, in the shallows, right? So where it was a little easier. And they were using those appendages to move around.
Half a wing, same things. So look at it this way. Feathers first appear not in birds per se, but in dinosaurs and carnivorous dinosaurs. And those feathers, their original function was not per se for flying. It was more for what feathers-- other functions of feathers as thermoregulation, insulation for warm blooded creatures, for displays, for courtship, and so forth. But certainly, not for flying.
What you see is the dinosaurs that are most closely related to birds all share a number of things. They share a very active lifestyle. So you look at their bones, histologically. You look at a cellular structure, and see just how fast growing they are. So they clearly had high metabolisms.
What they had were feathers. Clearly, all these carnivorous dinosaurs did have feathers. They have wing-like structures in their forearms, and wishbone-like structures in their chest cavity. They clearly are animals that were very rapid running predators. They could run and jump. They can climb the sides of trees.
So what we know for a fact is that these critters had bird-like structures throughout their body. What were they doing with it? Well, there are a couple of ideas. One idea is that, as they are running faster, wings evolve for ever longer periods of time off the ground to capture prey. The other is that these carnivorous dinosaurs may have been partially arboreal. That they would climb trees, and then jump off those trees. And wings evolve to support ever longer periods of powered flight after a period of gliding flight.
So you can envision many different kinds of intermediate functions that these appendages with feathers could have done. But what's inescapable is when we look at the fossil record. And we look at the genetic record. The organs that animals used for flight, just like the organs animals use to walk on land eons before, arose for a different purpose, in this case, for life on land.
[SWOOSH]
ASHLEY HAMER: Again, that was Neil Shubin, a biologist and author of the book, Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA. You can find the link to pick it up in today's show notes. And tomorrow, Neil Shubin will be back to tell us about the viral DNA lurking in our genomes. And how the heck it got in there. Well, you'll have to tune in to find out.
[SWOOSH]
NATALIA REAGAN: Well, let's recap today's takeaways.
ASHLEY HAMER: Well, we learned that there are even better planets out there than Earth when it comes to supporting life. Scientists have discovered 24 super habitable planets that make the cut. They're looking at factors like, what kind of stars the planets are near, how close they are to those stars, how big the planets are, all sorts of stuff. And a lot of it makes these planets rank better than Earth does. But all of the life that we have ever known exists on Earth. And that's the best place for Earth life. So don't worry about it.
NATALIA REAGAN: Yeah, that's one of the things that I always tell my classes, is the environment shapes who and what we are. A lot of our behavior, a lot of our morphology, is very much dependent on the environment. And Earth is pretty great. You got to take care of it.
ASHLEY HAMER: Yeah, I mean, everybody talks about escaping to Mars. And it's like, Mars is not a good place to live. It's not ideal. We want to do as best we can with this planet.
NATALIA REAGAN: Yeah, I mean, I get it. I get the sexiness of it. Like, Oh, it's so cool. Let's leave this planet and go somewhere new and exciting. It's novel.
It's like, Oh, look, a new planet. It's shiny and new. And then you get there. And you're like, Oh, we have to live in caves, because we're going to die of radiation if we stick outside. Who wants to be cave people? Ashley, do you want to go live in a cave?
ASHLEY HAMER: No, I don't. This seems like the spacefaring version of selling your house, and living in an RV, and traveling the country. It'll be like, Oh, out on the open road. Wait, I don't have a toilet.
[LAUGHS]
NATALIA REAGAN: Speaking of life taking a long time to emerge and find its little ecological niche, we learned that wings and limbs evolved all before flight and terrestrial living did. And these morphological structures were actually kind of repurposed into wings and the legs, as animals continued to evolve. I found this to be super fascinating. Because it makes me wonder are there any anatomical things that we have that we're going to repurpose? Like, I'm going to turn my arm into maybe a crab limb, as we're going to talk about later in future episodes. I'm going to gain exoskeleton.
ASHLEY HAMER: Right. It's like when you use your car key as an ice scraper.
NATALIA REAGAN: Right.
ASHLEY HAMER: Sometimes you just have a tool and it's useful for something else.
NATALIA REAGAN: I'm going to buy you an ice scraper for Christmas.
[LAUGHS]
I know what I'm getting you. But what I'm going to get you is a giant key shaped ice scraper. So you're still going to feel at home, OK?
ASHLEY HAMER: Perfect. Yes, great. I appreciate the thoughtful gesture.
[LAUGHS]
NATALIA REAGAN: But yeah. I mean, even the stuff about feathers being on dinosaurs and not necessarily having the purpose to have anything to do with flight. To actually get mates in a courtship, hey, baby check out my cool feathers, rather than like, I'm flying. I'm fluffy.
ASHLEY HAMER: Or it's warmth, which makes me just think about penguins. And were dinosaurs more like penguins that were just like shivering from the cold, like cuddling up to each other? I love that image.
NATALIA REAGAN: Yeah, Jeanette and Carol, my house dinosaurs, as it gets cold, I see them-- They're molting right now, actually. And they're very cold. I can see. They go in earlier at night right now, because they're just like, I'm cold. It makes me sad. Maybe that's why-- maybe the dinosaurs just wanted to move to Mars where they could live in caves and be warm all the time.
ASHLEY HAMER: It could have been.
NATALIA REAGAN: It could have been.
[SWOOSH]
Today's first story was written by Grant Curran. And edited by Ashley Hamer, who's the managing editor for Curiosity Daily.
ASHLEY HAMER: Scriptwriting by Natalia Reagan. And editing by Jonathan McMichael. Our producer is Cody Gough.
NATALIA REAGAN: Join us again tomorrow to learn something new in just a few minutes.
ASHLEY HAMER: And until then, stay curious.
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